EVALUASI PRODUKTIVITAS TANAH – TANAMAN Mk. Stela-smno.fpub.jun2013

EVALUASIPRODUKTIVITAS

TANAH – TANAMAN

Mk. Stela-smno.fpub.jun2013

CPI = CROP PRODUCTIVITY INDEX RATING

Sumber:.

Nilai CPI menyediakan informasi ranking relatif tanah-tanah berdasarkan potensinya

untuk produksi tanaman.

Indeks ini dapat digunakan untuk menilai potensial-hasil tanaman pada suatu tanah

dibandingkan tanah lainnya selama periode waktu tertentu.


Sumber:.

Productivity Index (PI)

Model Productivity index (PI) merupakan suatu ukuran yang diturunkan dari produktivitas

tanah. Asumsi mendasar dari model PI ini adalah

bahwa hasil tanaman merupakan fungsi dari pertumbuhan akar, yang selanjutnya

pertumbuhan akar ini dikendalikan oleh kondisi lingkungan tanah.


Sumber:.

CPI menunjukkan produksi pertanian setiap tahun, relatif terhadap tahaun dasar tertentu (misalnya

2004-2006). Indeks ini melingkupi semua tanaman, kecuali

tanaman pakan ternak.

Regional and income group aggregates for the FAO's production indexes are calculated from the underlying values in international dollars, normalized to the base period 2004-2006.


Sumber:. http://www2.bot.or.th/statistics/Download/EC_EI_010_ENG.PDF

Indeks produksi tanaman merupakan indikator tingkat produksi tanaman.

Indeks ini mencerminkan perubahan volume produksi dan siklus produksi.

The index covers 21 major crops and 20 vegetables and fruits, accounting for 67.7% of total value of agricultural

produc ts.

Monthly index is calculated, then quarterly and yearly indices are derived as the average of monthly series.

Data can be dated back to 1988.


Sumber:.

Data sekunder dari instansi resmi pemerintah dapat digunakan untuk perhitungan. Indeks dihitung dnegan formula Laspeyres, tahun

dasarnya misalnya 1988.

Produksi bulanan tahun dasar (1988) merupakan rata-rata total-produksi setiap tanaman selama seluruh tahun.

Weight applied to each product is the relative value-added of each product to that of the entire agricul tural sector as appeared in the

national account disseminated by the National Economic and Social Development Board (NESDB).

Formula yang digunakan adalah sbb:


Sumber:.

dimana

= CPI untuk bulan t,

= Kuantitas produk tanaman i bulan t pada tahun sedang berjalan

= Kuantitas produk tanaman i pada tahun dasar 1988

= Bobot produk i pada tahun dasar 1988

n = Banyaknya produk tanaman yang dipakai dalam perhitungan.

Sumber:. http://www.fao.org/docrep/V9926E/v9926e05.htm#TopOfPage

ASPEK –ASPEKFISIKA

PRODUKTIVITAS TANAH

ASPEK FISIK PRODUKTIVITAS TANAMAN

Sumber:http://www.fao.org/docrep/V9926E/v9926e04.htm.

Hubungan Sumberdaya Tanah dengan Sistem Pertanaman

Pandangan tradisional tentang pengaruh tanah ialah bahwa “tanah” menyediakan “peluang” atau “kendala” bagi tipe-tipe sistem-pertanaman yang dapat diimplementasikan dan

produktivitasnya.

A more responsible view is that 'the soil' combines various properties which interrelate and are directly influenced by

the procedures of cropping.



Dampak thd produktivitas

tanaman

Efek pd TanahPengelolaan

Agrokimia

Kehilangan hara

Olah Tanah

Beban kendaraan

Penyingkapan muka tanah

Hara tidak seimbang

Siklus Hara lambat: Waktu lebih lama untuk

melepaskan kembali hara yg diikat tanaman

sebelumnya menjadi tersedia bagi tanaman

sekarang

Ketersediaan air tanah berkurang.

Kemungkinan genangan meningkat dan

anaerobiosis

Pemadatan tanah, pori tanah berkurang

Penghancuran pori tanahPemadatan: kekuatan tanah

meningkat

Kehilangan bahan organik

Kehilangan hara anorganik

Organisme tnh yg berasosiasi dnegan akar tanaman berkurang:

Fiksasi N, Fasilitator P

Kelimpahan dan jumlah Organisme tnh dekomposer

berkurang

Agregat tanah hancur, membentuk kerak

permukaan

PORI TANAH & KARAKTERISTIK AIR

Tanah tersusun atas tiga bagian: bahan mineral, bahan organik dan rongga (disebut pori tanah).

Peranan relatif dari bagian-bagian ini beragam dengan tipe-tipe tanah , tetapi biasanya pori menempati separuh dari volume

tanah yang teksturnya medium.

At optimum water content for plant growth, approximately half the pore space is filled with water and half with air.

The proportions of water and air can change rapidly depending on weather, evapotranspiration and other factors.



Dimensi (ukuran, bentuk dan tatanan) dan banyaknya ruang pori sangat penting dalam menentukan lengas-tanah dan struktur-tanah.

Porositas merupakan volume rongga tanah (ruang pori). Pori ini dinyatakan dalam hubungannya dengan keseluryuhan volume tanah.

Kapasitas menyimpan air suatu tanah tergantung pada porositasnya, dan distribusi ukuran porinya. Pori-halus menahan air dnegan

tegangan lebih besar daripada pori besar.

The moisture (or water) potential is the amount of energy required to remove water from a soil; field capacity is the water-holding capacity

after a free-draining soil has been allowed to drain. The suction corresponding to this state has variously been defined as 0.33, 0.1 and 0.05 bar and so the convention used should always be checked. Wilting

point, beyond which plants cannot exert sufficient suction to remove water from a soil, is generally considered to correspond to a suction of

15 bar.



1 Equivalent particle size = 3.2 x pore size (assuming spherical, uniform size particles).2 Based on equation: Pore diameter (mm) = 0.30/soil water tension (kPa).

Sumber:.

Kelompok ukuran-pori tanah dan fungsinyaDiameter Pori tanah

(mm)

Fungsi Equivalent particle atau

Ukuran Agregat1

Sebab-sebab biologis (if not due to natural

particle arrangement)

Equivalent soil water2

tension (kPa)

>0.5 Aeration and water transmission

>1.6 (mostly gravel size, some coarse sand size)

ants, worms <0.6

0.50-0.05 Water transmission (infiltration, permeability)

0.16-1.6 (mostly coarse sand size, some fine sand size)

roots 0.6-6.0

0.0005-0.05 Water storage 0.0016-0.16 (mostly silt and fine sand size, some clay size)

lateral roots, root hairs

6.0-600

< 0.0005 Residual (bound) water, unavailable to plants

<0.0016 (mostly clay size)

fungal hyphae and bacteria

>600

Nilai-nilai WHC dari berbagai kelas tekstur tanah (diadopsi dari Salter & Williams 1967)

Kelas Tekstur Tanah Kapasitas Lapang (10 kPa) (gravimetric)

%

Tititk Layu (gravimetric) %

Air tersedia per meter Tanah

Coarse sand 8 4 80Sand 14 4 150Loamy sand 18 7 160Sandy loam 26 9 180Loam 30 13 180Silty loam 34 16 200Sandy clay loam 26 15 150

Clay loam 34 18 180Silty clay loam 43 20 190Sandy clay 29 19 140Clay 42 25 180


Nilai-nilai Konduktivitas Hidraulik jenus berdasarkan Tekstur dan derajat Struktur Tanah.

1 Strongly structured polyhedral subsoils, e.g. Krasnozem.TEKSTUR TANAH Structure Infiltration Permeability (mm/h)

Sand Apedal Very rapid >120 can be measured >250 Sandy loam Weakly pedal Very rapid >120

Apedal Rapid 60-120 Loam Peds evident Rapid 60-120

Weakly pedal Mod. rapid 20-60 Apedal Mod. rapid 20-60

Clay loam Peds evident Mod. rapid 20-60 Weakly pedal Moderate 5-20 Apedal Slow 2.5-5

Light clay Highly pedal Moderate 5-20 Peds evident Slow 2.5-5 Weakly pedal Very slow <2.5

Medium to heavy clay Highly pedal Slow 2.5-201 Peds evident Very slow <2.5 Weakly pedal Very slow <2.5

Clay Sodic and saline Moderate 8.0

Sodic Very slow <2.5 Highly sodic Extreme <1.0 Sumber:http://www.fao.org/docrep/V9926E/v9926e04.htm.

Air tanah tersedia (ASW) adalah jumlah air yang tersedia untuk diserap oleh akar tanaman, yaitu air yang ditahan dnegan tegangan antara

titik layu dna kapasitas lapang.ASW ini beragam dnegan tipe tanah dan biasanya berkorelasi dnegan

kandungan liat dan struktur tanah. ASW juga beragam dnegan perlakuan tanah, karena ukuran dan distribusi pori dalam topsoil

mencerminkan “terbukanya permukaan”, pembasahan-pengeringan musiman, dan pengelolaan tanah.

Williams et al. (1983), studying the water content of 244 soil samples, found that the ASW of well-structured soils was one-third to twice as large as that in comparable (similarly-textured) poorly structured or

degraded soils. Bearing in mind that ASW varies with natural weathering and management, Table 8 gives typical values of ASW for

various soil texture classes.



Konduktivitas hidraulik (K) tanah merupakan kemampuan tanah merembeskan gerakan air menuruni gradien

tegangan. Nilai-nilai K yang tinggi berhubungan dnegan tanah-tanah yg strukturnya baik dan prositasnya kontinyu; kondisi ini memungkinkan laju infiltrasi air yang cepat dan

drainage yng cepat.

Earthworm channels, which can have populations of 500 m-2 in Mediterranean climates (Barley 1959), and continuous

deep voids left by dead roots (5-10 000 m-2) contribute greatly to hydraulic conductivity.

Nilai K beragam dengan tipe tanah dan pengelolaannya (Table 9).



Nilai-nilai K kurang dari 10 mm/h termasuk RENDAH dan senderung menyebabkan runoff setelah terjadi hujan atau

problem irigasi, kalau intensitas hujan sekitar 10 mm/h.

K values of 10 to 20 mm/h can give intermittent runoff (a downpour falls at about 50 mm/h) while values up to 120

mm/h are associated with occasional, increasingly rare runoff.

Nilai-nilai K lebih dari 120 mm/h dapat membantu drainage reguler hingga groundwater, menyebabkan masalah

potensial untuk tanah yang dipupuk dosis tinggi, pupuk kandang, limbah , herbicide dan pesticida.



Both soil water content and saturated hydraulic conductivity generally relate to the number and continuity of pores, particularly the larger macro-pores. It is, however, difficult to measure these soil attributes and they are highly location-specific, so that variability is great and

they sometimes have little interpretive value.

Moran et al. (1988), however, in a study of a soil in a wet-and-dry environment, show that a soil treated with minimum tillage had more

pores, identified directly by image analysis, and higher hydraulic conductivity, measured in the field, than did a similar soil traditionally

cultivated.

Gambar berikut menunjukkan dampak pengelolaan terhadap karakteristik pori tanah dan air tanah.



Penampang vertikal tanah : Penampang vertikal tanah diambil dari perlakuan “direct drill (DD)” (a) dan tanah yg diolah konvensional (b)

di lokasi yang sama. Nilai konduktivitas hidrauliknya berturut-turut adalah 42.5 dan 5.0 mm/h (Moran et al. 1988)


PASIR: Butir lepas, terasa kasar dan cukup besar ukurannya untuk dapat diloihat secara individual butirannya; pasir kasar mempunyai

ukuran partikel 2 - 0.2 mm dan pasir halus 0.2 - 0.05 mm. Silt: imparts a smooth, soapy or silky and only slightly sticky feeling, silt grains cannot be individually detected; their particle sizes range

from 0.05 to 0.002 mm. Clay: gives a sticky feel to the soil. Clay particles are less than 0.002

mm diameter. These solid fractions contribute to the consistence and strength of the

soil, and their packing determines bulk density.

Bobot isi merupakan ukuran pemadatan atau pemampatan tiga komponen tanah. BI tanah dipengaruhi oleh komponen-komponen

tanah, nilai-nilai BI yang menghambat penetrasi akar berkisar mulai dari BI = 1.4 g cm3 pada tanah-tanah liat hingga BI = 1.8 g cm3 pada

atanah-tanah berpasir.



Soil strength is the resistance of soil to shearing or structural failure. This reflects the friction which is built up between the soil and an implement, and

depends on the density, and the roughness and shape of the soil particles. The shear strength of an individual clod decreases with wetting but, more

importantly, the strength of the bulk soil increases with increasing moisture to about the lower plastic limit (known to field operators as the 'sticky

point'), at which each particle is surrounded by a film of water which acts as a lubricant.

Kekuatan tanah menurun drastis mulai dari suatu titik tertentu hingga batas atas-plastisitas, dimana tanah menjadi viscous.

Perbedaan kandungan lengas-tanah antara batas atas plastis dan batas bawahnya disebut INDEKS PLASTISITAS, yg mencerminkan “daya-olah”

suatu tanah. Besarnya nilai indeks plastisitas tanah mengisyaratkan perlunya banyak

energi untuk mengolah tanah.



STRUKTUR Tanah dan Pertumbuhan Tanaman

Sifat fisik tanah mempengaruhi pertumbuhan akar dan batang secara langsung dan tidak langsung, misalnya melalui

drainage yg buruk menyebabkan pori tanah dipenuhi air dan tanaman menderita akibat anaerobiosis.

Root growth has been described under various soil physical conditions, but relationships have only rarely been

established between features such as crop yield, root growth and soil pore size distribution or conductivity, a more

aggregate measure.



Akar dapat tumbuh memanjang ke arah bawah dengan kecepatan 8 cm/d, misalnya, kedelai yang tumbuh pada

tanah lempung-debu dalam suatu rhizotron (Kaspar et al. 1978).

Deep-rootedness and maximum rooting depth reflect soil properties (for example, roots will not grow through pores

that they cannot deform to a larger diameter than the root).

Kedalaman maksimum perakaran tanaman beragam dengan spesies tanaman dan tipe tanah.



Akar tanaman gandum mampu menembus lapisan tanah sedalam 0.8 m pada tanah-tanah yg teksturnya berat (halus) dan mampu

menembus hingga kedalaman 1.2 m pada tanah pasir berlempung (Rickert et al. 1987); tetapi biasanya ditemukan suatu varietas

tanaman mempunyai kedalaman akar yg konsisten pada tipe-tipe tanah yang serupa dalam tahun tanam tertentu (Hamblin and Hamblin 1985) atau dalam suatu tipe tanah tertentu selama

beberapa tahun. (Pearson et al. 1991).

Angus et al. (1983) found that rice and six dryland crops (mung bean, cowpea, soybean, groundnut, maize and sorghum) extracted different amounts of stored soil water (ranging from 100 mm for rice to 250 mm

for groundnut) and that extraction was, in part, related to rooting depth.



The spread of roots with age can be related to the growth (increase in weight) of the whole plant, and to accumulated temperature or growing day-degrees (GDD); indeed, there is some evidence that

temperature influences the direction of newly-appeared roots as well as the rate of appearance and extent of growth (Tardieu and Pellerin

1991). Clearly, however, there are factors other than plant size, temperature and soil which influence root proliferation. Otherwise the plants sown at three different times of year in the same soil would align their root

growth along a single growth-GDD relationship.

Faktor-faktor lain, seperti panjang hari, mungkin sangat penting, biasanya digunakan untuk menjelaskan hubungan antara

pertumbuhan tanaman dan struktur tanah.



Persebaran akar gandum dengan umur, dan efek pengolahan tanah terhadap pertumbuhan akar (Pearson et al. 1991)


Pengolahan tanah dapat mempengaruhi panjang akar, meskipung efeknya baru muncul dalam tiga tahun.

Perbedaan porositas tanah dapat diukur pada dua perlakuan pengolahan tanah : Pada tahun pertama ternyata pertumbuhan akar dan infiltrasi air (K sekitar 5 mm/h) sama besarnya pada kondisi olah

tanah minimum dan pengolahan konvensional.

By the third year, when differences were measured between roots, infiltration rates were 84 mm/h in minimum tillage and 0.2 mm/h

under conventional tillage.

Despite the differences in root growth there were no substantial differences in grain yield, reflecting the overall constraint of climate in

the semi-arid environment.



Sumber:.

Values of air-filled porosity (%) and bulk density (g cm3) which are critical and which limit root growth for various soils (Source: Pierce et al. 1983)

1 "Critical" is defined as causing <20% reduction in root growth; "limiting" is about the value at which root growth ceases.

Texture class Non-limiting Critical1 Limiting Air-filled porosity Fine loamy 20 10 5 Coarse silty 20 10 5 Fine silty 20 10 5 Clay:

35-45 15 10 5 >45 15 10 5

Bulk density Sandy 1.60 1.69 1.85 Coarse loamy 1.50 1.63 1.80 Fine loamy 1.46 1.67 1.78 Coarse silty 1.43 1.67 1.79 Fine silty 1.34 1.54 1.65 Claye:

35-45% 1.40 1.49 1.58 45% 1.30 1.39 1.47

Peningkatan kerapatan tanah atau kekuatan tanah dapat menghambat penetrasi akar, sehingga membatasi volume tanah yang dapat

dieksploitasi oleh tanaman dan air tersedia. Biasanya sulit mengkuantifikasikan hubungan antara sifat tanah ini dnegan

pertumbuhan tanaman. In the cases of bulk density and strength, particularly, a gross measure of either for an undisturbed mass of soil

can give only a remote indication of what a root encounters.

A determination of gross bulk density does not assess whether a root is growing within a pore (in which case it may deform surrounding soil

before its radial environment reaches the density or strength of the gross soil) or if it is growing within the soil material, in which case it

has already exerted a radial force equivalent to that measured for the gross soil.



Efek bobot isi tanah dan kekuatan tanah terhadap proses perkecambahan dan pertumbuhan panjang batang juga dipelajari.

Batang (Shoot) mampu memanfaatkan pori makro tanah dengan tidak dibatasi oleh kondisi tanah secara keseluruhan.

Nilai-nilai aktual lokal yg menghambat pemanjangan batang kecambah (shoot) tampaknya sangat kecil, misalnya, 0.76 kPa (Addae and Pearson 1992). Nilai-nilai ini berasal dari kajian pada kondisi yg

terkendali, bebeda dnegan kondisi aktual di lapangan.

The relative ranking of genotypes is, however, the same when under near-critical stress as when growing with virtually no mechanical stress. Genotypes suited to stressful situations may be selected,

therefore, by screening at a single soil strength (Addae and Pearson 1992).



Hubungan antara kekuatan tanah dengan panjang akar relatif tanaman jagung (Kang and Ghuman 1991)


TABLE 11. Grain and stover yield (t/ha) of maize and seasonal water runoff and soil loss under maize grown with and without alley cropping, with two tree legumes, and

tillage in Nigeria (Source: Kang and Ghuman 1991) .1 Seasonal rainfall (March-July 1988) = 704.2 mm.


Treatment Maize Runoff1

(mm [% of rainfall])

Soil loss (t/ha)

grain stover

Without alley cropping

Tilled control 2.3 3.1 66.0 (9.4) 6.18

No-tillage 2.4 3.2 5.6 (0.8) 0.43

Alley-cropped

2 m Gliricidia 3.2 4.6 4.8 (0.7) 0.57

4 m Gliricidia 2.8 4.2 23.1 (3.3) 1.44

2 m Leucaena 3.4 4.9 2.6 (0.4) 9.17

4 m Leucaena 3.1 3.9 10.7 (1.5) 0.82


Tanaman dapat mempengaruhi kualitas tanah melalui ground-cover, kedalaman perakaran, dan sifat-sifat tanaman

lainnya. The crop attributes that most influence soil physical

properties are speed of establishment and development of foliage cover.

Rapid establishment and growth minimizes topsoil structural decline and soil erosion by wind and water.

Thereafter, deep-rooting directly affects soil structure, particularly if deep-rooted crops, such as safflower, are grown in rotation as a

'biological plough' to create macropores and these are minimally disturbed before the next crop is sown.



Sumber:.

TABLE 12. Desirable crop attributes that sustain soil productivity ASPEK FISIK PRODUKTIVITAS TANAMAN

Attribute Contributing characteristicRapid establishment (Relatively) large seed for establishment and seedling vigour;

abundant seed for propagationGroundcover to reduce soil exposure, suppress weeds

Early branching; perhaps rhizomes or stolons; horizontal leaves (high canopy-extraction coefficient)

Low requirements for nutrients · Colonization by associative bacteria (e.g., Brachyrhizobiun), micorrhizae (e.g., Glomus) and free-living organisms (e.g., Azospirillum)· Low P, K, etc. requirement per unit dry matter, e.g., high "phosphate efficiency"

Efficient water use Short growth duration (to utilize residual moisture after crop); high water use efficiency

Deep rooting to reduce water table (salinity) and recover nutrients at depth and increase macropores

Vertical root distribution; roots penetrate high impedence soils

Useful products High leaf/stem ratio; edible seeds; easily digestible; no nutritional compounds in material for livestock; leaf retention on stems for cut and carrying to livestock

Non-host for diseases and pests of main crop (to break disease cycle) or decoy (to attract diseases from concurrent crops)

Botanically unrelated to main food crop(s)

Suppress other species Allelopathy (leachates, exudates which suppress or kill other plant species); also physical attributes (as above)

Indikator Lapangan problematik Fisika-tanah

Indikator lapangan yang lazim bagi kondisi fisika tanah yang buruk adalah:

1. Patchiness or absence of vegetation. This can be an obvious sign of degraded structure or other factors. When structural, it may reflect surface structure degradation (see previous sections) or non-wetting characteristics which give rise to poor infiltration, or subsoil impermeability.

2. Vegetasi bergulma. Cyperaceae atau Juncaceae dapat mencerminkan jeleknya struktur tanah, karena mereka tumbuh subur kalau air tergenang di permukaan tanah, menunjukkan jeleknya laju infiltrasi atau adanya lapisan bawah yang kedap air.



Indikator Lapangan problematik Fisika-tanah


3. Erosi permukaan dan erosi alur. Erosive runoff may be symptomatic of poor surface structure. The turbidity of water in ponds and lakes after rain may be a good indicator of erosion.

4. Kerak tanah di permukaan. 5. Permukaan tanah yang mengeras. 6. Infiltrasi yang jelek dan genangan air. This may be indicated by

puddles following rain in an area where one would expect rapid infiltration, or by wetting to only a shallow depth (as seen when dug with a spade).




7. Warna tanah permukaan pucat dan tidak ada bahan organik. The surface of degraded soils may be brittle and pale, lacking organic matter and having lost clay either through eluviation (differential movement downwards) or by water or wind erosion.

8. Berbongkah-bongkah (Cloddiness). This may be apparent if after a single cultivation, large, tough clods are formed requiring further cultivation to form a reasonable seedbed.




9. Peetumbhuhan akar terhambat. This can be seen by digging with a narrow-faced spade and washing the roots free of soil. The root mass can be restricted to the upper soil or be constricted in particular places such as a less pervious layer, above and below which the roots may proliferate.



TABLE 16. Examples of farmer concepts/statements concerning aspects of sustainable crop production (Source:

Fujisaka and Garrity 1991)

Tanaman dan Hara dalam tanah

1. Ubikayu dapat mengasamkan tanah.2. Ubikayu “menguras” hara dari tanah.3. Padi lebih toleran tanah-tanah masam dibandingkan

Jagung.4. Rice is more vigourous on an area previously planted

in tomato.5. Intercropping bagus kalau ketersediaan haranya

cukup


Pengurasan Hara Tanah:

1. Kesuburan tanah telah digunakan oleh tanaman.2. Tanah menjadi lemah.3. Fertility is spotty.4. Soils are overtrained.5. Tanah-tanah menjadi semakin lebih tua.6. Poor, but not used up, in the sense of the hardest

part within a log.


Contoh Konsep/Pendapat Petani tentang aspek-aspek Produksi Tanaman Berkelanjutan (Fujisaka and Garrity 1991)

Contoh Konsep/Pendapat Petani tentang aspek-aspek Produksi Tanaman Berkelanjutan (Fujisaka and Garrity 1991)

Lahan bero (kosong) - Fallows:

1. Biomasa gulma yg terdekomposisi membantu memperkaya tanah.

2. Lahan istirahat sehingga tanah dapat menyimpan sejumlah hara.

3. Kaya karena beristirahat.4. Fertility is added and the soil is made cool.5. The soil is slightly enriched if left a short time.


TABLE 16. Examples of farmer concepts/statements concerning aspects of sustainable crop production (Source: Fujisaka and

Garrity 1991)

Gulma - Weeds1. Padi dirugikan oleh akar-akar cogon (I. cylindrical).2. Tanah menjadi jelek kalau cogon dominan.3. D. longiflora and cogon consume soil nutrients and destroy soil

quality.4. Kemasmaan tanah meningkat kalau cogon dominan.5. Gula kurus pada tanah-tanah tidak subur.6. R. cochinchinensis rapidly produces seed; thus, easily soars in

population; if not weeded, it exceeds the height of rice or corn.7. Fertility is added and the soil is made cool" (re. Calapogonium

spp.).8. Tanah menjadi baik kalau ada gulmua/rumput mempunyai bintil

akar.


TABLE 16. Examples of farmer concepts/statements concerning aspects of sustainable crop production (Source:


Erosi Tanah:1. Tanah terkikis dan terangkut ke tempat lain.2. Hara terangkut.3. Tumbuhan tererosi bersama dnegan tanahnya.4. Soil was drawn down and fertility was washed out.5. The land was shaven and eroded after trees were

removed.6. Pupuk terkumpul (di bagian bawah petakan) karena

terbawa air hujan.


Tabel 16. Examples of farmer concepts/statements concerning aspects of sustainable crop production (Source:


Kontrol Erosion :1. Pisang dan Kelapa lebih baik karena mereka mampu

menahan tanah.2. Pengolahan menurut kontur mengurangi kehilangan

erosi.3. Jalur-jalur rumput dapat mengurangi efek erosi4. Trees planted above and below fields can decrease

erosion effects.5. Banana planted above and below fields can decrease

erosion effects.Sumber:http://www.fao.org/docrep/V9926E/v9926e04.htm.

Aspek-aspek penting dalam memelihara atau ameliorasi sifat fisika tanah

Pengelolaan: Pencegahan degradasi sifat fisika tanah

Pilihan Pola Pertanaman: 1. Rotations + sequential cropping2. Mixed cropping3. Relay cropping4. Alley cropping, parkland + agroforestry



Budidaya Tanaman :

1. Olah Tanah + pengelolaan residu2. Waktu Tanam3. Seed quality and soil organism symbioses4. Pupuk anorganik5. Pengelolaan Bahan Organik6. Cultivar: ground cover, complementarity with other crops7. Manajemen gulma+hama secara hayati.




Inter-crop ley and fallow :1. Cover crop2. Pasture ley3. Maintenance of surface litter in absence of living

vegetation




Mulsa :1. Mulsa hidup in situ2. Tumbuhan pupuk hijau3. Residu / seresah In situ4. Residu dari tempat lain5. Limbah ternak, kompos6. Limbah industri7. Penutup anorganik, mis. Kerikil




Amelioration to control damage :Pengelolaan erosi oleh air :1. Pengolahan tanah menurut garis kontur2. Saluran air bertingkat3. Guludan4. Saluran air berumput5. Ponds .




Ameliorasi untuk Mengendalikan Kerusakan

Pengelolaan erosi oleh angin :1. Wind-breaks + interplanting dengan pohon2. Penanaman kembali dnegan Semak + pohon3. Penutupan muka tanah4. Pematang / tanggul



TABeL 19. Aspek-aspek yg dipertimbangkan dalam ameliorasi sifat fisika tanah



Ameliorasi untuk Mengendalikan Kerusakan

Pengelolaan Permukaan Tanah1. Menutupi dengan residu, limbah dari tempat lain, dll.2. Inter-cropping dan mulsa

Pemadatan :3. Pengolahan tanah secara dalam, subsoiling4. Menanam tumbuhan yang perakarannya dalam



ASPEK – ASPEK BIOLOGIS DAN KIMIA

PRODUKTIVITAS TANAH


BIOLOGI TANAH & LINGKUNGAN MIKRO

Bahan organik, organisme mikro dan makro (mis. fungal hyphae dan invertebrates), detritus dari fungi dan binatang, bacteria, dan eksudat

biologis, semuanya membantu menstabilkan struktur tanah.

The role of each part of the biomass differs according to its size.

Broadly, large aggregates greater than 250 m m diameter (macro-aggregates), are stabilized by their inherent physical structure , wetting

and drying cycles, and organic matter.

Mikro-agregat (< 250 mm) distabilkan oleh bentuk-bentuk hidup atau mati dari akar, fungi, invertebrata dan mikroba.

ASPEK BIOLOGIS DAN KIMIA PRODUKTIVITAS TANAH


FIGURE 22 - Model of aggregate organization with major binding agents indicated (Source: Tisdall and Oades 1982) - Major binding

agent

Tanah

Pori


Model organisasi agregat tanah dengan bahan perekatnya (Tisdall and Oades 1982) – Akar dan Hifa (keduanya bahan

organik hidup)

Akar

Hifa

Agregat tanah


Model organisasi agregat tanah dengan bahan perekatnya (Tisdall and Oades 1982) – Plant and fungal debris encrusted with inorganics

(bahan organik persisten)

Hifa

Bakteri

Paket-paket

partikel liat


Model organisasi agregat tanah dengan bahan perekatnya (Tisdall and Oades 1982) – Residu mikroba dan fungi encrusted with inorganics

(bahan organik persisten)

Partikel Liat

Limbah Mikroba (material humik)


Model organisasi agregat tanah dengan bahan perekatnya (Tisdall and Oades 1982) – Bahan amorf alumino-silikat, oksida-oksida dan polimer organik yg diserap pada permukaan liat dan ikatan

elektrostatika, flokulasi (bahan anorganik permanen)

Lempengan Liat

Cement = Perekat


Populasi organisme tanah dari semua ukuran berhubungan secara fungsional melalui peranannya dalam degradasi

bahan organik tanah.BOT ini meluputi bahan tumbuhan hidup dan mati, serta

biomasa organisme lainnya hidup dan mati.

Gambar berikut menyajikan jaring-jaring makanan (food web ) dalam tanah.

This shows that animals such as nematodes and some fungi feed directly on live plants while other fungi and bacteria

feed predominantly on litter.



Representation of detrital food web in shortgrass prairie. Fungal-feeding mites are separated into two groups (I and II) to distinguish the slow-growing cryptostigmatids

from faster-growing taxa. Flows omitted from the figure for the sake of clarity include transfers from every organism to the substrate pools (death) and transfers

from every animal to the substrate pools (defaecation) and to inorganic N (ammonification). Source: Doran (1987)


Earthworms and other large invertebrates create, and inhabit, burrows and pores, and are very mobile.

The most notable of these are termites, which are divided into three groups according to the structure of their nests: those that build mounds (a) above ground, (b) on the soil

surface, and (c) below ground.

Small arthropods, microfauna and fungi live mostly in larger voids and in association with roots.



Foster (1988) reviewed the location of the various types of soil-dwelling organisms and found that fungi, which constitute about 80% of the biomass in many soils, tend to be restricted to the rhizosphere

of roots, to larger pores between aggregates and to the surface of aggregates.

Bacteria, by contrast, are found on roots in the rhizosphere, in small colonies in the larger micropores, within aggregates and on and within

cell debris. For more information on location refer to Foster (1988).

Smiles (1988) describes the physics of the micro-environment of small soil organisms.



BAHAN ORGANIKTumbuhan dan hewan menyediakan bahan organik bagi tanah. Bahan

organik tanah dapat dibedakan berdasarkan struktur kimiawinya, misalnya substansi humik kaya lignin yang sukar lapuk.

The standing crop of litter in semi-arid grasslands is usually more than 3 t/ha and in temperate dry steppe may exceed 11 t/ha (e.g.,

Klemmedson 1989). There has been much debate about the relative contents of organic matter in tropical and temperate soils.

Within those wet-and-dry climates that have hot summers assisting rapid decomposition, there is no evidence of inherently lower levels of

organic matter in the tropics than in comparable temperate regions (Juo and Payne 1993).



EFEK BAHAN ORGANIK TERHADAP KESUBURAN TANAH (Young 1989)

Efek-efek Primer KonsekwensiEfek FisikaBinding of particles, root action leading to improved structural stability, balance between fine, medium and large pores

Improved root penetration, erosion resistance and moisture properties; water-holding capacity, permeability, aeration

Efek KimiaNutrient source, balanced supply, not subject to leaching, with slow, partly controllable, release

Including better response to fertilizers, non-acidifying source of N, mineralization of P in available forms

Complexing and enhanced availability of micronutrientsIncreased cation exchange Better retention of fertilizer nutrients

Improved availability of P through blocking of fixation sitesEfek Biologis

Provision of a favourable environment for N fixationEnhanced faunal activity


Kowal and Kassam (1978) ; Juo and Payne (1993) mengkaji peranan bahan organik di tanah-tanah tropika. Ternyata BOT

mempunyai berbagai efek yang saling bertalian dengan kesuburan tanah.

In particular it should be noted that both chemical and physical effects are of relatively great importance in the soils

of the semi-arid tropics because these generally have low cation exchange capacity (effective CEC values less than 14

meq/100 g clay).



Kepentingan relatif seresah tanaman (crop residue) dan pupuk kandang sebagai inputs bahan organik, beragam di

antara sistem-sistem pertanaman dan beragam secara spatial di salam suatu sistem pertanaman.

The figure illustrates the flow of litter, manure and by-products (such as dung cake for fuel) in Indian villages

practising approximately one-third single cropping and two-thirds double cropping.

Sebagian besar biomasa bagian-tanaman di atas tanah dimakan oleh ternak, tetapi sejumlah yg hampir sama

biomasa bawah tanah menjadi cadangan BOT.



Energy flow through the agro-ecosystems. Values are means from five villages = 1 SE (× 106 KJ/yr/ha cultivated land solar radiation = 6.5 x 1010 kJ/yr/ha (Source: Singh

and Singh 1992)


Pola aliran biomasa pupuk kandang dan sisa panen tanaman di lahan pertanian sangat beragam sesuai dengan praktek

budidaya pertanian di daerah iklim basah dan kering.Biasanya semua biomasa akar ( misal, 40% dari total

pertumbuhan tanaman) dan 10-30% dari biomasa tajuk tanaman di-daur-ulang dalam sistem pertanaman semusim.

Where alley cropping and agroforestry are practised, values are more variable, but possible inputs could be very

significant where the trees, from which the litter is taken, are grown away from the annual crops.

ASPEK BIOLOGIS & KIMIA PRODUKTIVITAS TANAH


Kalau dua-pertiga daun-daun pohon legume dipanen setiap tahun, nilai biomasa seresah ini sangat besar dan kualitasnya lebih baik dibanding dengan jerami sisa panen tanaman semusim lain; biomasa legum

ini sebagai pupuk hijau di-daur-ulang di lahan.

Tree root material is not available for decomposition in the crop field unless it is spatially overlapping (e.g. as an intercrop), in which case the trees will compete

with the crop for soil nutrients, water, light and space.



Produksi biomasa dedaunandari Pohon Multiguna (Young 1989)

Country Land use Tree t/ha/yearMalaysia Plantation Acacia mangium 3.06Philippines Plantation Albizia falcataria 0.18Costa Rica Hedgerow intercropping Calliandra calothyrsus 2.76Philippines Plantation Gmelina arborea 0.14Indonesia (Java) Plantation L. leucocephala, A.

falcataria, Dalbergia latifolia, Acacia auriculiformis

3.00-5.00

Cordia alliodora 2.69Plantation crop C. alliodora + cacao, 6.46

Costa Rica combination Erythrina poeppigiana, 4.27E. poeppigiana + cacao 8.18

Nigeria Hedgerow intercropping Cajanus cajan 4.10Nigeria Hedgerow intercropping Gliricidia sepium 2.30Nigeria Hedgerow intercropping L. leucocephala 2.47Nigeria Hedgerow intercropping Tephrosia Candida 3.07India Plantation L. leucocephala 2.30


Laju dekomposisi biomasa seresah daun tergantung pd kondisi lingkungannya, terutama suhu dan lengas tanah.

Kedua kondisi lingkungan tanah ini mempengaruhi penghancuran fisik seresah dan menentukan populasi & aktivitas hewan tanah serta fungi tanah yang “makan”

bahan organik tersebut. Decomposition also varies with plant type and age of litter, being

slower for heavily lignified material. The specific properties of litter from different species, and the

generally exponential form of litter decay (the rate of decomposition slowing with time) lead to values that suggest

half-lives of litter ranging from 1 to about 10 years .



Beberapa faktor yg mempengaruhi kecepatan dekomposisi BOT dan siklus hara adalah spesies tanaman, suhu dan

lengas tanah, serta faktor pengelolaan tanaman.

Ada empat cara untuk mengelola residu tanaman: 1. Stubble mulch in which residues are left standing; 2. Surface mulch, where above-ground residues are cut and left on

the top of the soil after harvest; 3. Incorporation by ploughing; and 4. Cut-and-carry, in which surface residue is removed and (if not used

for livestock or thatching, etc.) returned as a surface mulch about planting time for the subsequent crop; this is usually combined with ploughing of below-ground residues.



Konstante dekomposisi, k, untuk biomasa jenis legum tropis. Nilai-nilai ini dihitung dnegan persamaan exponential untuk dekomposisi BO

dengan memakai data dalam pustaka ( Juo and Payne 1993) Species Location Mean annual

rainfall Mean annual

temperature °C k/year

Gliricidia sepium Ibadan, Nigeria 1250 23-31 8.48

Flemingia congesta Ibadan, Nigeria 1250 23-31 3.66

Cassia siamea Ibadan, Nigeria 1250 23-31 2.17

Lonchocarpus cyanescems

Ibadan, Nigeria 1250 23-31 8.87

Inga vera El Verde, Puerto Rico

4000 22 1.65

Inga sp. And Erythrina (mixed)

Caracas, Venezuela 1200 20 3.01

Erythrina sp. (mixed with non-legumes)

Caracas, Venezuela 1200 20 3.81

Inga edulis Yurimaguas, Peru 2200 26 0.91

Cajanus cajan Yurimaguas, Peru 2200 26 1.45

Erythrina sp. Yurimaguas, Peru 2200 26 3.72

ORGANISME TANAH YG BERASOSIASI DNEGAN TANAMAN

Bacteria dan NitrogenCropping in dryland regions needs nitrogen to be economically

successful (e.g., Keating et al. 1991). Two sources of nitrogen are from organic matter (Chapter 2, section Soil pores and water characteristics)

and from nitrogen-fixing bacteria associated with plant roots. Bradyrhizobium and Rhizobium species infect plant roots forming galls or nodules, and fix nitrogen from the soil atmosphere directly to the

plants. Locally-adapted, heat-tolerant strains survive from crop to crop in wet-and-dry climates and, whether established by natural colonization or

by inoculation of the crop seed at sowing, they subsequently fix variable quantities of nitrogen.

Kalau infeksi bakteri dapat efektif, bacteria biasanya dapat memfiksasi sekitar 70-100% dari total nitrogen yg digunakan oleh tanaman, proporsi ini lebih rendah kalau ada aplikasi pupuk N anorganik.


Efek N mineral tanah dan pupuk N terhadap produktivitas N tanaman dan proporsi (P) serta jumlah N-tanaman yg berasal dari fiksasi N2

( Peoples and Craswell 1992)


Species Location Level Total crop N2 fixed Soil mineral N

(kg N/ha) Fertilizer N (kg N/ha)

N (kg N/ha/crop)

Proportion Amount (kg N/ha/crop)

Groundnut India - 0 196 0.61 120 100 210 0.47 99 200 243 0.42 102

Chickpea Australia 10 (to 120 cm) 114 0.85 97

326 184 0.17 33

0 109 0.80 87 50 110 0.55 60

100 104 0.29 30 Soybean Australia 70 (to 120 cm) 230 0.34 78

260 265 0.06 16

India - 0* 63 0.29 18 100 148 0.26 28

- 0** 89 0.48 43 100 115 0.24 28

ORGANISME TANAH YG BERASOSIASI DG TANAMAN

The extent of the effectiveness of infection of legume crops in the wet-and-dry tropics needs to be surveyed.

Temperate research indicates that nitrogen fixed by bacteria ranges from 20 to 120 kg N/ha in a growing season for annual crops (Table

24). In the semi-arid tropics, amounts of nitrogen fixed per hectare range

from none, where nodulation is ineffective, to 16 kg N in soybean naturally colonized by rhizobia, to 84 kg N when inoculated.

Fiksasi Nitrogen pada kedelai dan kacang-tanah sebesar 50-70 kg N/ha/musim tanam dilaporkan di Senegal (Gigou et al. 1985).

Bakteri fiksasi Nitrogen berasosiasi dnegan pohon legume dapat memfiksasi sejumlah nitrogen seperti kedalai dan kacangtanah.


Fiksasi Nitrogen oleh pohon dan belukar. Values are per growing season or per year unless the number of months is given in brackets

(Young, 1989 ; Peoples and Craswell 1992)


Species N fixation (kg N/ha/year) Acacia albida 20 Acacia mearnsii 200 Allocasuarina littoralis 220(?) Casuarina equisetifolia 60-110 Coffee + Inga spp. 35 Coriaria arborea 190 Erythrina poeppigiana 60 Gliricidia septum 13 Inga jinicuil 35-40 Inga jinicuil 50 Inga jinicuil 35 Leucaena leucocephala 100-500 Leucaena leucocephala (in hedgerow intercropping)

75-120

Leucaena leucocephala 100-13 (6)

ORGANISME TANAH YG BERASOSIASI DG TANAMAN

Fungi, Algae dan Hara

Berbagai jenis fungi membantu penyerapan hara oleh akar tanaman, terutama phosphorus. Banyak jenis fungi hidup

berasosiasi dengan akar tanaman.

One group, vesicular arbuscular micorrhizal fungi (VAM), form both vesicles and arbuscules (knot-like structure) on

the surface and within the root. They also colonize soil animals including earthworms and

woodlice.



Mikroba ini banyak dijumpai dalam topsoil hingga kedalaman 10 cm (Habte 1989). Mereka ini membantu penyerapan hara, terutama

fosfor dari tanah yang miskin fosfor. Mereka ini juga menyediakan proteksi bagi tanaman inangnya, keberadaannya dapat menurunkan

kolonisasi oleh patogen. Ellis et al. (1985) also found that wheat plants inoculated with VAM were more drought-tolerant than plants without VAM. Importantly,

comparisons of conventional cropping systems using inorganic fertilizers and herbicides with organic systems not using herbicides have found much higher levels of infection of crop roots by these

beneficial fungi in the organic system (Ryan et al. 1994).

Pengelolaan organisme tanah yg bersifat asosiatif dan menguntungkan menjadi bagian penting dari sistem pertanaman yg lestari.


Frequency (%) fungi VAM dalam macro-invertebrata tanah yang diambil dari ekosistem alam dan pertanian di Ohio (data are combined from 1986 and 1987

samplings) (Source: Rabatin and Stinner 1989)


Taxa Ekosistem

Conventional tillage maize

No-tillage maize

Pasture Old field

Lumbricidae (earthworms)

25.0 83.3 50.0 75.0

Isopoda (woodlice)

100.0 35.7 64.7 36.8

Carabidae (ground beetles)

2.1 19.8 14.5 12.8


GULMA, HAMA & PENYAKIT TANAMAN

Gulma, hama dan penyakit semuanya bersaing dnegan tanaman atau secara langsung mereduksi vigour tanaman. Banyak hama dan

penyakit bersifat “soil-borne”.

Weed life-cycles depend on replenishment of the soil seed bank and survival of the seeds against natural decay, predation by soil animals

and depletion by human management, particularly cultivations.

Ecological weed control thus aims to minimize recruitment of new seed into the soil as a long-term strategy as well as trying to reduce

artificially the size of the weed seed bank in the soil.


KETERSEDIAAN HARA DALAM TANAH

HARA ANORGANIKHara anorganik dalam tanah dapat berbentuk ion dan mineral misal. Oksida-oksida, silikat dan fosfat; keduanya dijerap pada permukaan

partikel liat dan bahan organik , dan ada dalam larutan tanah. Sebagian besar dari hara, terutama nitrogen, ditemukan dalam bahan organik tanah, sehingga BOT dan organisme tanah sangat penting bagi

per-hara-an tanah.

Clay particles, because of their crystalline structures, carry an inherent electrical charge. This results in attractive forces (mainly van der Waals forces) and repulsive forces (electrostatic forces) which give clay species their particular characteristics.

The inherent surface charge also causes a layer of associated ions to align next to the solid particles forming a so-called diffuse double layer because it consists of a

relatively inexchangeable layer (the Stem layer) closest to the surface of the particle and an outer, readily exchangeable layer, of varying thickness, called the diffuse

layer. Sposito (1984) explains this more fully.


Penjerapan (Adsorption) merupakan akumulasi neto materi pada ruang antara fase padatan dan fase cairan. Ion-ion yang mudah

ditukar dijerap dg kekuatan “lemah” pd permukaan koloid tanah dan mudah dapat digantikan dnegan jalan pencucian menggunakan larutan

elektrolit. KTK tanah merupakan jumlah mole ion yg dijerap dan dapat

digantikan dari suatu unit massa tanah; ion-ion seperti ini lazim disebut “ion mudah ditukar”.

Sposito (1984) notes that 'Much controversy exists over the surface chemical significance of ion exchange capacities'. The maximum

surface charge measurement indicates a soil's potential to adsorb ions while its actual capacity, which is more relevant agriculturally, has a

lesser value. Table 28 gives representative cation exchange capacities (CECs) for selected soil orders. It is notable that though the CEC of each

order ranges widely, the predominant soils in wet-and-dry climates have low CECs.



Nilai-nilai KTK lapisan tanah permukaan (molC/kg) (: Sposito 1984)


ORDO TANAH KTKAlfisols 0.1 2 ± 0.08Aridisols 0.16 ± 0.05Entisols 0.13±0.06Histosols 1.4±0.3Inceptisols 0.19±0.17Mollisols 0.22±0.10Oxisols 0.05±0.03Spodosols 0.11 ±0.05Ultisols 0.06 ±0.06Vertisols 0.37 ± 0.08


Proporsi kation tukar dalam KTK beragam dengan pH tanah; proporsi basa-tukar yg mudah tersedia menurun dari sekitar 1 pada pH 8 dan 0.5 pada pH 6 menjadi sekitar 0.2 pada pH 4.5. Pada kondisi pH kurang dari 6 terjadi peningkatan ion-

ion aluminium yang dapat bersifat toksik.

The electrical conductivity and CEC of a soil are related to its clay content (e.g., Rhoades 1990a). Similarly, because of the electrical

charge of the clay particles, a high but variable percentage of the soil organic matter is bound to them. It may be as high as 90% ; and there

are the two postulated main ways that organic matter is bonded to clay. These are weak anion exchange and strongly-held ligand

exchange which is a form of chemical bonding.



Proporsi C-organik dalam tanah yang berbentuk Kompleks Liat-Organik.

1 Defined as the material sinking when the soil was ultrasonically dispersed in an organic liquid of density 2 g/cm3.


Percent organic carbon in soil

Percent soil carbon in clay-organic complex1

Podzol 1.5 18Solonized brown soil 1.5 77

Grey clay soil 1.1 91Terra rossa 2.8 82Groundwater rendzina

5.4 69

Black earth 1.8 82Krasnozem 4.9 90Red brown earth 2.5 66

Liat dan bahan organik tanah mempunyai muatan listrik, dan keduanya mempunyai sumbangan besar dalam menentukan

kemampuan tanah menahan hara-tersedia dan stabilitas struktur tanah.

Pieri (1992) mengusulkan bahwa stabilitas struktur tanah (untuk tanah-tanah di Afrika yg ditelitinya) dapat

dideskripsikan dengan nilai kritis S lebih besar dari 9, dimana S adalah rasio bahan organik dengan (liat plus

debu) , dinyatakan dalam persentase.



Diagram jembatan anionik : Pertukaran Anion. R adalah Koloid humik poli-anionik humic colloid.


Diagram jembatan anion: Pertukaran ligand. R adalah koloid humik poli-anionik.


Tingkat kritis BOT untuk mempertahankan stabilitas fisik struktur tanah (Pieri 1992)


Akar tanaman menyerap hara anorganik dari larutan tanah (kecuali legumes, yang mampu memfiksasi nitrogen langsung dari udara

tanah). Unsur hara dapat tersedia bagi tanaman kalau ia berbentuk ion bebas dan berada dalam zone perakaran.

Ion-ion hara dalam tanah bergerak memasuki zone akar melalui pergerakan air tanah, dan ion hara memasuki tanaman melalui

evapotranspiration.Diffusion along concentration gradients is important for less-mobile ions such as phosphorus, particularly where soil solution concentrations are

weak and root densities are high (i.e., the transport path is short). Sposito (1984) and others give calculated values for the diffusivity of nutrients.

Diffusion times range from 1 day for an ion to move 3 mm (which is comparable with the time it would take to move by convection in the

mass flow of water) for nitrate to about 200 days for potassium, magnesium and molybdenum, and to thousands of days for other

nutrients. Sumber:. http://www.fao.org/docrep/V9926E/v9926e05.htm#TopOfPage


pH rendah mempengaruhi akar tanaman secara langsung karena efek konsentrasi H+ thd integritas membran sel akar dan kapasitas

pertukarannya. Kemasaman jug mempengaruhi akar secra tidak langsung melalui dua cara. Ia mengubah ketersediaan ion dalam larutan tanah (membuat

spesies Al tersedia yg toksik bagi tanaman plants). Ia juga mempengaruhi mineralisasi melalui proton yg bersaing dengan cations

untuk mendapatkan ligand yg terlarut dan gugus fungsional pd permukaan yg bermuatan.

Soil pH also affects micro-organisms, and thus the speed of transformations, for example, those between nitrate and ammonium.

Poor plant growth on acid soils may thus be caused directly by hydrogen ions, by toxicities of aluminium or manganese, or through

deficiencies of calcium, magnesium, potassium, phosphorus, nitrogen or trace elements.



Chase et al. (1989) describe these relationships for sandy Sahelian soils. Variation in pH across distances of 15 m can be as much as pH 4.5 to 7.5, with associated decreases in

aluminium and hydrogen ions, and increases in crop productivity.

Nilai kritis pH yang mempengaruhi pertumbuhan tanaman ternyata beragam dnegan jenis tanaman, cultivar dan tipe

tanahnya.

Tingkat kritis ini dapat sebesar pH 5 - 5.5 untuk jenis tanaman yg tidak toleran Al , tetapi jenis tanaman lainnya

yang toleran mempunyai nilai kritis pH 3.9 - 4. Sumber:. http://www.fao.org/docrep/V9926E/v9926e05.htm#TopOfPage


Bahan organik tanah berhubungan dengan partikel (mineral) tanah secara kimiawi dan secara fungsional.

BOT berhubungan erat dengan berbagai problematik biologis dan ketersediaan hara dalam tanah.

Rates of loss of organic matter independent of erosion tend to be slow, but important as they are cumulative.

Pada kondisi lingkungan lahan-kering di Afrika Barat, laju kehilangan BOT dapat mencapai 2-4% per

tahun. Sumber:. http://www.fao.org/docrep/V9926E/v9926e05.htm#TopOfPage

INDIKATOR PROBLEMATIK BIOLOGIS DAN HARA

TABLE 31. Annual rate of organic matter loss measured in the field in the savannah area (Source: Pieri 1992)



Place and source Dominant rotation Clay + silt(%)

(0-20 cm)

Annual rate of loss Notes k (%) No. of years

Burkina Faso Ploughed

Sorghum monocropping

12 1.4 10 No fertilizer


12 1.9 10 Low rate manure


12 2.6 10 High rate manure


12 2.2 10 m + crop residues

Cotton-cereal 19 6.3 15 Much erosion

Cameroun Cotton-cereal 17 3.2 5 No fertilizer

Cotton-cereal 17 2.9 5 Fertilizer

Cotton-cereal 17 2.5 5 Fertilizer + kraal

Côte d'Ivoire Cotton-cereal - 2.6 5 Low rate manure

Cotton-cereal - 2.3 3 Low rate manure

Cotton-cereal - 0.4 3 Improved fallow

Larson dan Pierce (1991) mengusulkan bahwa seperangkat data yg dikumpulkan secara analitik sangat penting untuk

memantau kelestarian tanah. They include two measures of organic matter among the ten

attributes that they consider essential (Table 32). Their concept of requiring agreed minimum data sets is

consistent with the approach to assessing sustainability .

Kalau seperangkat data tersebut telah diperoleh (Larson and Pierce 1991), setiap atribut tanah ditentukan dengan waktu referensi tertentu (T0) dan perubahan kondisi tanah dapat diukur selama periode waktu tertentu (T1), misalnya 1 – 10

tahun.



TABLE 32. Soil attributes and standard methodologies for their measurement to be included as part of a minimum data set (MDS) for

monitoring soil quality (Source: Larson and Pierce 1991)


Soil attribute MethodologyTotal organic carbon Dry or wet combustionLabile organic carbon Digestion with KCINutrient availability Analytical soil testpH Glass electrode-calomel electrode pH meter

Electrolytic conductivity Conductivity meterTexture Pipette or hydrometer method

Plant-available water capacity Determined in field best or from water desorption curve

Structure Bulk density from intact soil cores field measured permeability of Ksat

Strength Bulk density or penetration resistance

Maximum rooting depth Crop specific - depth of common roots or standard

Pengukuran C-organik tanah secara langsung dianggap tidak-efektif biaya dan tidak informatif.

It is more likely that surrogate measures are adequate and, if sufficiently simple and cheap, have some likelihood of being

used. Pieri (1992) suggests that a bleached (possibly brittle) soil

surface and plant deficiency symptoms are useful surrogates for loss of organic matter, low CEC and soil nutrient imbalances.

Kehilangan BOT biasanya dibarengi dengan degradasi struktur tanah, indikator-indikator seperti turbiditas air permukaan (mis. Air

sungai) dianggap sangat berguna.



Hara Mineral dan Problematik Kesuburan Tanah (Source: Pieri 1992)



General problems Signs of simple problems Where they occur Probable causes

Limitation of nutrient supply to crops· Nutrient imbalanceDeficiency in organic matter

Bleaching and destruction of soil surface

Senegal, Niger, Burkina Faso, Mali

Insufficient return of crop residuesAccelerated mineralization of dry matterToo little fertilizer

Defisit N (S) N (S) deficiency in cereals, legumes and cotton

Throughout area Too little N (S) applied in fertilizers or manures. High C/N ratioVery little N fixationLeaching of nitrate

K-Ca-Mg deficit K deficiency, Al toxicity Frequent K deficiency in cottonAl toxicity in groundnut and cotton (Senegal)

Severe leaching of Ca, Mg, K.Fertilizers low in Ca, Mg, K.

· Low buffer capacityProgressive drop in CEC

Loss of fine mineral and organic soil particles

Senegal, Mali, Cote d'Ivoire, Burkina Faso, Niger, Chad

Poor erosion controlRapid mineralization

Acidification Senegal, N Cote d'Ivoire, Burkina Faso, Chad

NO3/Ca + Mg leachingFertilizers too low in Ca, MgToo little or no liming

Tanah-tanah Marjinal

Nutrient deficiencies Senegal, N Togo, S Mali, Burkina Faso

Land shortagePoor cultivation

Indikator defisiensi hara meliputi : warna (mis. Kemerahan unt defisiensi kalium); pucat (gejala umum, tetapi

merupakan gejala khusus defisiensi N); daun-daun kecil dan tanaman kerdil.

Other symptoms, such as leaf curling and accelerated dropping of older leaves, may also be helpful but might

equally indicate water deficits.

There are several publications with photographs of nutrient deficiencies; these, however, might require further tailoring

to specific combinations of crops and soils.



Gejala efek kemasaman tanah dicirikan oleh tanaman kerdil, muka tanah bersih vegetasi, dan jenis-jenis gulma yg toleran

asam tumbuh lebih baik. Salinitas juga dicerminkan oleh perubahan vegetasi seperti

pohon mati tanpa alasan yg jelas atau meningkatnya populasi herba yg toleran garam.

Other symptoms of salinity include: waterlogged or bare soil; livestock congregating and licking the soil surface for

salt; visible salt crystals; the smell of salt; and clear catchment water because salt settles sediment.



Pengelolaan unt Memelihara Biologi dan Hara Tanah

The aim of management should be to create balanced organic matter and mineral budgets. It should ensure that, over several years (a

complete crop rotation), soil organic matter is not depleted and that nutrients added equal or exceed those removed by cropping or lost in

various ways.

When managing organic matter farmers should recognize that the effects of animal and human manure, sewage sludge and plant

residues last longer than those of green manure crops.

Manfaat pupuk hijau biasanya berlangsung selama satu atau dua musim, karena bahan organik ini dimasukkan ke tanah sebelum dewasa (tua) dan berlignin. Efek jangka panjang bahan organik

terhadap organisme tanah juga ada. Sumber:. http://www.fao.org/docrep/V9926E/v9926e05.htm#TopOfPage


Aspek-aspek yg dipertimbangkan dalam memelihara dan ameliorasi biologi tanah dan hara tanah


Pemeliharaan: Pencegahan Degradasi1. Pemilihan Tanaman· Preference for rotations and intercropping with several species, as for Table 19· Inclusion of legume in rotation

2. Praktek Budidaya Tanaman· Aplikasi pupuk anorganik untuk menjaga neraca hara yg netral· Konservasi seresah tanaman · Aplikasi kotoran manusia dan hewan· Incorporation of organic wastes from industry and cities· Olah tanah minimum· Pengelolaan hayati hama dan gulma· Mengurangi laju pengasaman melalui pemilihan jenis tanaman, pengelolaan seresah dan pupuk.

3. Pengelolaan Air· Water harvesting· Minimization of salinity, if a problem is likely, through seasonal leaching and other practices

Aspek-aspek yg dipertimbangkan dalam memelihara dan ameliorasi biologi tanah dan hara tanah



Ameliorasi untuk mengontrok kerusakan :

1. Ketidak-seimbangan dan defisiensi hara· Berdasarkan gejala visual, aolikasi pupuk anorganik· Mengubah pola tanam untuk mengurangi efek kemasaman

2. Degradasi permukaan tanah melalui kehilangan BOT, erosi tanah oleh air dan angin :

Aplikasi bahan organik berupa limbah organik, mulsa, tanaman penutup tanah dll.

Pola dan Pergiliran Tanaman mempengaruhi ketersediaan hara tanah.

Diversitas pertanaman meningkatkan jumlah dan ragam organisme tanah dan mengurangi hama dan penyakit.

Soil acidification and salination are extreme cases of nutrient imbalance and, unlike other deficiencies, cannot be corrected simply

by adding mineral fertilizers.

Teknik pengelolaan tanah unt mengurangi asidifikasi: (a) Mengurangi produksi proton dengan jalan meminimumkan pencucian nitrat

(problem khusus di daerah iklim musimaan basah-kering); (b) Menghindari penggunaan pupuk ammonium dan mengurangi akumulasi bahan

organik; (c) Mengapur tanah.



EVALUASI PRODUKTIVITAS TANAH-TANAMAN

Pengelolaan bahan organik sisa panen untuk

mengembalikan kesuburan tanah

EVALUASI PRODUKTIVITAS TANAH – TANAMAN Mk. Stela-smno.fpub.jun2013

Documents

Transcript of EVALUASI PRODUKTIVITAS TANAH – TANAMAN Mk. Stela-smno.fpub.jun2013