Faktor lingkumgan tanaman dapat dibagi/digolongkan menjadi:

• Environmental conditions (Faktor lingkungan yang mengendalikan penyerapan sumber daya = resource); seperti: – Abiotic (e.g., weather, certain soil

characteristics)

– Biotic (e.g., weeds, pests, pathogens, soil organisms)

• Consumable resources (Sumber daya yang dapat dikonsumsi) : CO2, light, water, dan nutrients

Environmental conditions: merupakan benda/faktor, baik biotik ataupun abiotik, yang mempengaruhi laju dan efisiensi penangkapan/kehilangan dalam memanfaatkan sumber daya alam

Resources merupakan sesuatu yang dikonsumsi tanaman dalam pertumbuhan dan perkembangbiakannya.

Resources

Sesuatu (SDA) yang sangat dibutuhkan tanaman agar mampu tumbuh berkembang untuk menghasilkan produk pertanian (a harvestable yield).

Pada sebagian besar agro-ecosystems, produktivitas tanaman ditentukan oleh ketersediaan salah satu atau lebih SDA yang dibutuhkan tanaman, seperti nutrisi, air, dan cahaya matahari.

Jumlah hasil tanaman yang diperoleh merupakan fungsi dari tingkat keterbatasan SDA yg tersedia bagi tanaman dan efisiensi penggunaan SDA.

Environmental factorsI. CLIMATEImportant features of climate include: • light• temperature• humidity• precipitation• Wind

Climate includes both:• Resources [light, precipitation (actually, soil

water is the resource)]• Conditions (e.g., temperature, day length,

humidity, wind)

Environmental factors

II. SOILS

1. SOIL CONSTITUENTS2. MINERAL (INORGANIC) FRACTION3. SOIL ORGANIC MATTER4. SOIL STRUCTURE5. SOIL TYPES6. SOIL ORGANISMS7. SOIL pH

Environmental factors

III. RESOURCES• Light• Carbon dioxide• Water• Nutrient

CLIMATE

I. LIGHT (Solar Radiation)• The seasonal distribution of light is

controlled by latitude. [How does the light environment of tropical latitudes differ from that of temperate and boreal latitudes?]

• Plants (including many crops) show photoperiodic responses to day length, particularly in their phenology.

CLIMATE

I. LIGHT (Solar Radiation)• Phenology has been defined as

"the sequence of development events during the plant's life cycle as it is determined by environmental conditions" (Hall, 2001); these include flowering, bolting, tuber formation, etc.

• "Long day" (LD) plants; "short-day" (SD) plants; and "day neutral" (DN).

CLIMATE

II. TEMPERATUREThe seasonal and diurnal variation in

temperature increase with latitude Temperature also decreases with

increasing altitude The rate of temperature change with

altitude is called the lapse rate and is about 1 0C 100 m-1 for dry air and about 0.6 0C 100 m-1 for wet air.

CLIMATEII. TEMPERATURE• Most plant processes have an optimum

temperature. • Respiration increases with increasing

temperature.• Plant development is mostly controlled by

temperature. Plants sense environmental temperature in terms of degree days --the cumulative number of the degrees above a base or threshold temperature.

• Crop plants exposed to higher than normal temperatures develop at a more rapid rate (for example, flower earlier), which could decrease yield.

CLIMATE

III. PRECIPITATION

GO TO ANOTHER SLIDE :

RAINFALL N CROPPING SYSTEMS IN INDONESIA…Ю

SOILSI. SOIL CONSTITUENTS/KOMPONEN TANAH• Atmosphere/Atmosfer• Water/Air• Mineral (inorganic) materials/Mineral• Soil organic matter (SOM)/Bahan Organik• Soil organisms/Organisme dalam tanahAtmosfer tanah sangat berbeda dengan kondisi

atmosfer bumi. Dalam atmosfer tanah, kadar CO2 lebih tinggi dan kadar O2 lebih rendah.

(The atmosphere below ground in the soil difference substantially from that aboveground. The soil atmosphere is higher in CO2 and lower in O2)

SOILSSoil provide an important environment for plants/crops due

to (Tanah menyediakan lingkungan yang penting bagi tanaman, karena alasan sbb) :

1. Plants need anchorage, so that there should be adequate soil layer. Tanaman memerlukan media tumbuh, sehingga dibutuhkan lapisan tanah yang memadai

2. Plants need water, so that soil should hold adequate water and supply. Tanaman perlu air, sehingga tanah harus mampu memegan dan menyediakan sejumlah air bagi tanaman.

3. Plants need oxygen for respiration, so that soil should be able to provide it without any interruption. Tanaman butuh Oksigen untuk respirasi, sehingga tanah harus mampu menyediakannya tanpa ada interupsi/ganggian

4. Plant roots release CO2 during respiration, and soil should be able to regulate the movement of this gas without allowing it to build up to toxic levels. Akar tanaman melepad CO2 selama melakukan respirasi, dan tanah harus mampu mengatur pergerakannya tanpa membiarkannya menjadi senyawaan toksik.

SOILS5. Plants need nutrients from soils, which are

absorbed by roots, so that soils should have some characteristics to supply and retain nutrients. Tanaman butuh nutrisi dari dalam tanah. OKI tanah haruslah memiliki sifat-sifat terkait dengan penyediaan dan penyimpanan nutrisi tanaman.

6. Plants add a lot of dead material (OM) and the soil should have able break them to some form so that they will not interfere with plants and their root systems. Tanaman menambah banyak bahan organik (organ tanaman yang mati) dan tanah harus mampu menguraikannya dehingga tidak mengganggu tanaman dan sistem perakarannya.

SOILS7. Some plants through root exudates add to soil toxic

chemicals (allelo-chemicals) and soil should be able to decompose them to avoid root damage. Beberapa tanaman, melalui eksudasi akar, menambah senyawaan toksik (allelo0chemicals) dan tanah harus mampu mendekomposisinya agar tidak merusak akar.

8. During heavy rainy periods, large volumes of water are added with a very high intensities and the soil should be able to handle these volumes without severe soil losses. Selama hujan lebat berlangsung dengan intensitas tinggi, ada penambahan air ke dalam tanah dalam volume banyak. OKI tanah harus mampu merubahnya sehingga tidak menimbulkan kerugian akibat hilangnya lapisan tanah atas.

SOILS9. There are toxic gases released when animal and

root systems grow in soils and soil should be able to either release these gases to atmosphere or convert to non-toxic form by other reaction. Ada beberapa gas toksis yang dikeluarkan oleh hewan atau akar tanaman dan tanah harus mampu melepaskannya ke atmosfer atau merubahnya menjadi senyawaan non-toksis.

10. When both plant and animals live in soil, it should be able to maintain suitable temperatures required by those living beings. Ketika tanaman dan hewan hidup di dalam tanah, maka tanah harus mampu menjaga temperatur tanah sedemikian rupa sehingga cocok bagi kehidupan mereka.

SOILSTherefore… Oleh karena itu ......Soils is suitable for everything at anytime. Tanah

selalu cocok bagi makhluk hidup It is required to treat the soil with the right

knowledge of it in order to receive benefits the mankind wants Perlu dilakukan perlakuan terhadap tanah berdasarkan pengetahuan yang benar aga diperoleh manfaat seperti yang diinginkan oleh manusia.

Soil always have many associations and interactions among these factors (physical, chemical, physico-chemical and biological factors). Tanah selalu memiliki berbagai assosiasi dan interaksi antara faktor-faktor: fisik, kimiawi, fisiko-kimiawi, dan faktor biologi tanah)

Physical factors/Faktor Fisik

Soil texture/ Tekstur tanahParticle size distribution (clay, silt and

sand)/Distribusi ukuran partikael tanah (lempung/liat, debu,dan pasir)

In general/Secara umum:Coarse sand (Pasir kasar) 0.25 – 2.0

mmFind sand (Pasir halus) 0.05 – 0.2 mmSilt (Debu) 0.002 – 0.05 mmClay (Lempung/liat) < 0.002 mm

Physical factors/Faktor Fisik

Bulk density and porosityKeduanya berkaitan dengan:1. Capacity for gas

exchange/Kapasitas pertukaran gas2. Root growth and penetration/

Pertumbuhan dan penetrasi akar3. Drainage and retain water/Drainase

dan penahanan/penyimpanan air4. Infiltration and percolation/Infiltrasi

dan perkolasi

Physical factors/Faktor FisikSoil structure/Struktur TanahComposition of pores and soil aggregates

(Komposisi pori-pori dan agregat tanah)Pores consist of (Pori tanah terdiri atas):Micro pores/Pori-pori mikro (capillary water

retained = pori berisi air kapiler)Macro pores/Pori-pori makro (gas exchange

and drainage = pertukaran gas dan drainase)

Crumb structure/Struktur remah – best for agriculture (baik untuk pertanian)

50 % each of micro and macro pores (Jumlah pori mikro dan makro, masing-masing 50%).

Physical factors/Faktor FisikSoil water content/Kadar air tanah• Saturated condition/Jenuh• Field capacity/Kapasitas lapang• Permanent wilting point/Titik layu permanenSoil temperature/Temperatur tanah• Increase root growth and activities/

Meningkatkan pertumbuhan dan aktivitas akar

• Increase microbial population/ Menngkatkan populasi mikroba tanah

• Increase organic matter decomposition/ Meningkatkan dekomposisi bahan organik

• Increase seed germination/ Meningkatkan perkecambahan biji

Chemical factors/Faktor KimiaNutrient contents in soil/Kandungan nutrisiGas content/Kadar gasChemical reactions/Reaksi kimiawi

Physico-chemical factors/Faktor fisiko-kimiawi

(good for agriculture)pH (6 – 7)CEC (Cation exchange capacity) (> 40

mg/100 g soil)EC (electrical conductivity) = water quality

parameter (0.4 – 0.7 m mhos/cm)

Biological factors/Faktor Biologi

Micro and macro both fauna and floraImportant activities/Aktivitas penting:• Mineralization of organic matter/ Mineralisasi bahan

organik• Nitrogen fixation in legumes / Fiksasi nitrogen dalam

legume• Micorrhyza promoting P absorption / Micorrhyza:

absorpsi P• Enzymes activities and nutrient transformation in soils /

Aktivitas enzym dan transformasi nutrisi dalam tanah• Improve porosity by earthworm (tunneling) /

Peningkatan porositas tanah oleh cacing tanah (pembentukan tunnel/saluran)

• Improve root absorption activities /Peningkatan aktivitas absorpsi di dalam tanah

RESOURCES/Sumber Daya Alam

Light/CahayaQuantity/Kuantitas• Full Sunlight/Cahaya penuh/langit cerah: 200-500

Wm-2 or 1000-2000 µmol m-2 s-1 (W = J s-1)• Cloudy sky/berawan: 20-90 Wm-2 or 100-400 µmol

m-2 s-1

• Seasonality/Sebaran musiman: The highest monthly (i.e., growing season) maximum light levels are at higher latitudes (Kuantitas cahaya bulanan tertinggi terdapat di daerah lintang tinggi).

Crop yields in the tropics (compared to temperate zones) are ultimately limited by (Hasil tanaman di daerah tropis (dibandingkan dengan zona temperate) sangat dibatasi oleh):

• incident radiation/ Cahaya datang• cloudiness-compare wet season and dry season

yields /Keawanan – bandingkan hasil tanaman musim kemarau dan penghujan

RESOURCES/SDAGrowth and Yield are ultimately related to light

interception. Pertumbuhan dan hasil tanaman sangat berkaitan dengan intersepsi cahaya. – At the leaf level: There is a minimum amount of light

required for a positive net photosynthesis to occur, called the light compensation point. Pada tingkat daun: ada jumlah cahaya minmal yang dibutuhkan tanaman agar diperoleh fotosintesa bersih positif (dikenal sbg: Titik kompensasi cahaya)

– At the canopy level: Some leaves in a canopy will be shaded by other leaves, some below, and perhaps some below the light compensation point. Pada tingkat kanopi: Beberapa daun akan ternaungi oleh daun d atasnya dan mungkin mendapatkan beberapa poin di bawah titik kompensasi cahaya.

• Rates of canopy photosynthesis are usually proportional to LAI. Laju fotosintesis kanopi biasanya proporsional dengan LAI

RESOURCES/SDA• At the crop level: Crop growth (and yield) is

generally a function of leaf-area duration (LAD), the area under a curve of LAI vs. time. Pada Tingkat tanaman: Pertumbuhan (dan hasil) tanaman umumnya merupakan fungsi dari Leaf Area Duration (area di bawah kurva dari LAI vs waktu

• LAD is proportional to the total amount of light energy absorbed during the crop's growing season, and thus to yield. LAD proporsional dengan total seluruh energi cahaya yang diserap tanaman selama masa pertumbuhannya dan tentunya juga hasil tanaman.

RESOURCES/SDA (CO2)The direct (physiological) effects of this increase in

atmospheric CO2 are Pengaruh fisiologis langsung dari CO2 atmosfer:

• increased rates of photosynthesis, especially in C3 plants, resulting in higher crop yields. Meningkatkan laju fotosintesis, khususnya tanaman C3, sehingga diperoleh hasil tinggi

• increased water-use efficiency. Meningkatkan efidiensi penggunaan air

• higher C:N ratios in plant biomass. Nisbah C:N pada biomassa tanaman lebih tinggi.

• Higher CO2 concentrations induce partial closing of the stomates, which increases the resistance to the flow of water vapor, reducing transpiration and thus increasing water-use efficiency (WUE). Konsentrasi CO2 tinggi penutupan stomata secara parsial, yang meningkatkan hambatan terhadap aliran uap air, sehingga menekan laju transpirasi dan alkhirnya meningkatkan WUE

RESOURCES/SDA• Higher leaf temperatures (caused by

stomatal closure) associated with increased [CO2] can lead to increased leaf turnover rate (higher leaf temperatures and more rapid leaf aging)/ Temperatur daun yg tinggi (disebabkan oleh penutupan stomata) yang disertai dengan peningkatan CO2 cenderung dapat meningkatkan laju turnover daun (suhu daun tinggi dan penuaan daun lebih cepat),

• Decreased specific leaf area, reducing the CO2-fertilization effect. Penurunan luas daun spesifik menurunkan pengaruh CO2 – pemupukkan.

RESOURCES/SDA

Soil Water/Air Tanah• Field capacity (FP) is the amount of water held in

a saturated soil after all excess water has drained off; the water potential at field capacity is -0.1 to -0.2 MPa. Kapasitas lapang (FP): jumlah air yang tersisa setelah kondisi jenuh air didrainase dan tidak menetes lagi. Water potensial pada FP: -(0,1) s/d –(0,2) Mpa.

• Permanent wilting point is the point at which a (particular) plant can no longer absorb water from the soil, for most plants in most soils the water potential at the permanent wilting point is about -1.5 MPa. Titik layu permanen: titik dimana, utk tanaman tertentu, tidak mampu menyerap air dari dalam tanah. Air biasanya tedapat pada poei-poei kapiler. Nilai potensial airnya berkisar – 1,5 Mpa.

RESOURCES/SDA• Available water is the amount of water between field

capacity and permanent wilting point. Air tersedia: kadar air tanah yang berada di antara FP dan titik layu permanen.

• Soil water content is influenced by both soil texture and soil organic matter (SOM). Kadar air tanah dipengaruhi oleh tekstur tanah dan bagan organik tanah.

• Fine-textured soils have a higher total pore volume, and hence can hold more water. Tanah bertekstur baik memiliki total pori tanah lebih banyak, sehingga dpt menahan air lebih banyak.

• Clay particles hold water more tightly. SOM functions similar to clay particles in affecting soil water-holding capacity and soil water potential. Partikel liat memegang air lebih kuat. Fungsi SOM mirip dengan liat dalam hal kemampuannya menahan air dan potensial air tanah.

RESOURCES/SDANutrition/Nutrisi• Macronutrients, those required in rather high

amounts by plants, are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Most fertilizers contain N, P, and/or K. Hara makro, hara yg dibutuhkan tanaman dlm jml banyak, meliputi: nitrogen (N), K, Ca, Mg, dan S. Biasanya, pupuk mengandung N, P, dan K.

• Micronutrients are elements that are also essential for growth but are required in lower amounts; these include iron (Fe), copper (Cu), zinc (Zn), boron (Bo), molybdenum (Mo), manganese (Mn), cobalt (Co), and chlorine (Cl). Hara mikro, hara esensial yg dibutuhkan tanaman dlm jml sedikit, contoh: Fe, Cu, Zn, Bo, Mo, Mn, Co, dan Cl.

Nutrient cycling/Siklus NutrisiRefers to the processes that transfer nutrients to and

from plants and the various soil (and atmospheric) pools. Merupakan proses perpindahan hara dari dan menuju ke bagian tanaman dan tanah (termasuk atmosfer)

These pools can be characterized as: Semua proses pada semua bagian tsb dicirikan oleh:

• active, inorganic forms and microbial biomass-very rapid turnover; aktif, perputaran antara bentuk anorganik dan mikrobial-biomassa sangat cepat

• slow, new crop residues and coarse particulate organic matter; and perlahan/lambat, sisa-sisa tumbuhan baru dan partikel bahan organikyang kasar

• Passive, fine particulate organic matter and humic substances-very slow turnover. Pasif; partikel halus dari bahan organik dan senyawaan humat – perputarannya sangat lambat.

Interactions between Resources and Environmental Factors

Crop yield is a function of resource use. In general, resource-use efficiencies are the products of resource uptake (capture) and resource utilization (biomass or yield produced per unit of resource captured) (Janssen, 1998). Hasil tnm merupakan fungsi dr pemanfaatan resources/ SDA. Scr umum, efisiensi pemanfaaran SDA merupakan hasil dari penyerapan/penangkapan SDA dan penggunaan SDA (biomassa atau hasil yg diperoleh per unit SDA yang ditangkap)

Yakni hubungan antara yield (Y) dan supply SDA (S) termasuk penyerapan SDA(U):

• Y/S = U/S (resource uptake) × Y/U (resource utilization efficiency)

• Y/U is the physiological RUE, whereas U/S is the ecological RUE.

Faktor-faktor yang berpengaruh terhadap hasil tanaman melipoti

beberapa tipe dan termasuk:• Resources not under grower control: light, CO2,

water (precipitation), nutrients released by mineralization. SDA yg tdk dpt dikendalikan oleh petani, seperti: cahaya, CO2, air (presipitasi), dan nutrisi yg dilepaskan melalui proses mineralisasi.

• Environmental conditions, not under grower control: temperature, wind, seasonality, topography, length of growing season, relative humidity; soil type, soil depth, SOM, soil pH; pest, weed and pathogen populations (in part). Kondisi lingkungan yg tdk dikendalikan petani: suhu, angin, musim, topografi, lama musim tanam, kelembaban, jenis tanah, solum tanah, SOM, pH tnh, hama, gulma, dan patogen.

• Resources under grower control: nutrients (from fertilizer), water (from irrigation). SDA yd dikendalikan petani: hara/pupuk dan air irigasi.

Faktor-faktor yang berpengaruh terhadap hasil tanaman melipoti beberapa tipe dan termasuk:

• Environmental conditions under partial grower control: pest, weed, and pathogen populations; SOM; soil structure; soil pH. Kondisi lingk dibawah kendali petani: populasi hama, patogen, dan gulma; SOM, struktur tanah, dan pH tanah.

• Crop varieties/ Varietas tanaman • Management: land preparation, choice of cropping

system; choice of cultivars; date of planting; plant population; timing of nutrient input; timing of pest, weed and pathogen control; date of harvest; management of residues. Pengelolaan: persiapan lahan, pemilihan sistem bertanam, pemikihan kultivar, saat tanam,populasi tanaman, saat pemupukan, saat penfendalianhama/penyakit dan gulma, saar panen, dan pengelolaan residu.

• Infrastructural or institutional factors: access to credit, suitable varieties, extension services, inputs, markets. Faktor infrastruktur atau institusional; kemudahan kredit bank, varieras yg cocok, penyuluhan, input, dan pasar.

Interaksi antar spesies dalam Agroecosystems

This part of the course considers some of the other organisms, in addition to crops and soil organisms, that occur in agroecosystems, particular herbivores (mostly insects) and their predators, and competitors (weeds). Pathogens are discussed only briefly.

Kecuali interaksi antara tanaman dan organisme dalam tanah, pada bagian ini akan dibicarakan interkasi dengan beberapa organisme lain yang sering terjadi di agroekosistem; khususnya herbivora (terutama insek) dan predator serta kompetitor (gulma) mereka. Patogen hanya dibahas secara singkat.

Herbivores/Herbivora• Why don't insects (and other herbivores)

consume all available plant biomass? That is, Why is the world green?-most likely answers are plant defenses that limit which herbivores can feed on which plants, and predators that keep herbivore populations in check.

• Mengapa tidak semua insek (dan herbivora lain) mengkonsumsi semua biomassa tanaman yang ada? Itulah sebabnya.. Mengapa dunia ini hijau? Jawaban yang mungkin mendekati kebenaran adalah bahwa tanaman mempunyai pertahanan yang membatasi herbivora mana yang dapat memangsanya dan predator apa yang mengendalikan popukasi herbivora.

Herbivores/HerbivoraGroups of herbivores:• Vertebrates-birds, mammals• Invertebrates-insects, arachnids (mites),

mollusks (snails, slugs). Of these groups insects cause the greatest crop losses in most agroecosystems.

Penggolongan herbivora:Vertebrata: burung dan mamalia Invertrebrata: insek, arakhnida (tungau), moluska (kerang,

siput). Dari kelompok ini, serangga menyebabkan kerugian tanaman terbesar di kebanyakan agroecosistem

Herbivores/Herbivora

Tanaman Strategi untuk mengatasi herbivora:Escape-pendek siklus hidupToleransi - Kompensasi thd kehilangan jaringanPertahanan - perlindungan jaringan

Masalah ekologi yang terkait dengan penggunaan insektisida :Resistensi terhadap insektisidaPemunculan hama tipe baru (kasus wereng)Wabah Hama sekunder

Integrated Pest Management (IPM).

Herbivores/Herbivora

Plant Strategies to cope with herbivory:• Escape-short life cycle• Tolerance--Compensation for tissue loss• Defense--protection of tissues Ecological problems associated with insecticide

use:1. Insecticide resistance2. Pest Resurgence3. Secondary Pest Outbreaks

Integrated Pest Management (IPM).

Competitors (Weeds)Characteristics of Weeds• High seed production, competitiveness, low

attractiveness, seed longevity, seed dormancy, rapid emergence.

• Most weeds evolved from early successional species; many are crop relatives

Karakteristik gulmaProduksi biji tinggi, daya kompetisi kuat, daya

tarik kurang, daya hidup biji sangat lama, dormansi biji, cepat berkecambah.

Kebanyakan gulma berperan dalam suksesi spesies sejak awal; Kebanyakan gulma berkerabat dekat dengan tanaman budidaya.

Competition/Niche Theory Two species can occupy the same habitat and

not compete if:• The species use different resources. This is

often true for animals, but seldom true for plants.

• Resources are sufficient for both. For example, plants in the desert seldom compete for light.

• The species obtain their resources from different parts of the habitat. I.e., the species have a somewhat different niche with respect to resource acquisition.

• Many plant ecologists (e.g., David Tilman) maintain that plant species specialize with respect to their ability to capture different resources. This is probably not true, however, for crops and weeds.

Kompetisi/Teori Niche (Ceruk) Dua spesies dapat menempati tempat/habitat yang sama

dan tidak berkompetisi jika:• Kedua spesies memanfaatkan SDA yang berbeda. Hal

ini sering terjadi pada hewan, untuk tanaman jarang atau bahkan mustahil terjadi.

• SDA (resources) tersedia dalam jumlah cukup (mencukupi kebutuhan keduanya). Sebagai contoh, tanam di padang pasir jarang berebut cahaya matahari.

• Kedua spesies mendapatkan kebutuhan mereka (SDA) dari bagian habitat yang berbeda; mereka memiliki niche/ceruk/wilayah tempat pengambilan SDA yang berbeda.

• Beberapa ahli ekologi tanaman (e.g., David Tilman) menyatakan bahwa spesies tanaman memiliki kemampuan yang spesifk dalam menyerap/menangkap SDA yang berbeda. Akan tetapi hal ini tidak benar, khususnya untuk tanaman dan gulma.

Competitors (Weeds)Weeds reduce crop yield by reducing the supply of resources through

competition.• Plants use common resources--Light, C02, Water, Nutrients.• Plants obtain resources from resource depletion zones, which depend

on root and shoot architecture, and on resource mobility.• Intensity of competition depends on the degree of overlap of resource

depletion zones.Gulma menurunkan hasil panen dengan mengurangi pasokan sumber daya alam melalui persaingan.Tanaman menggunakan sumber

daya umum- Light, C02, Air, Nutrisi.Tanaman memperoleh sumber daya alam dari zona yang

kekuranga sumber daya alam, yang tergantung pada arsitektur akar dan pucuk, dan mobilitas sumber daya.

Intensitas kompetisi tergantung pada derajat tumpang tindih zona deplesi sumber daya.

Pathogens/Penyebab Penyakit• Penyakit menurunkan ecological resource use

efficiency dengan mengurangi penyerapan SDA melalui beberapa mekanisme: penutupan jaringan pembuluh angkut, merusak akar, menghambat pertumbuhan akar, atau menurunkan luas daun (LAI).

• Tanaman memiliki sistem pertahanan thd patogen baik secara morfologi maupun kimiawi.– Morphological-- cuticle– Chemical-- both constitutive and inducible

(inducible defenses against pathogens are called phytoalexins)

• These defenses most effective for aboveground pathogens.

Pathogens/Penyebab Penyakit

• Diseases reduce ecological resource use efficiency by reducing resource uptake by various mechanisms: obstructing vascular tissues, damaging roots, restricting root growth, or removing leaf area.

• Plants possess morphological and chemical defenses against pathogens:

• Morphological-- cuticle• Chemical-- both constitutive and inducible

(inducible defenses against pathogens are called phytoalexins)

• These defenses most effective for aboveground pathogens.

Fungsi Keanekaragaman pada Agroecosystems

Most agroecologist menyatakan: Kenekaragaman merupakan faktor penentu atau kunci dari keberlanjutan (sustainability).

Keanekatagaman pada cropping systems:• Monoculture (Monokultur):

– Continuous (Secara terus menerus)– Crop Rotation -- short rotations vs. long rotations

Polyculture (polikultur):– Intercropping– Agroforestry– Home-garden systems

The Functional Role of Diversity in Agroecosystems

Diversification is the Key to sustainability, according to most agroecologists.

Diversity in cropping systems:Monoculture:• Continuous• Crop Rotation-short rotations vs. long

rotationsPolyculture:• Intercropping• Agroforestry• Home-garden systems

Keanekaragaman didefinisikan sebagai:• Richness/kekayaan - number of species/

banyaknya spesies• Equitability / kesetaraan -- number and relative

abundance / jumlah dan jumlah relatif• Connectance/Keterkaitan or

complexity/kompleksitas – contohnya: kompleksitas pada jejaring makanan

Fungsi ekosistem biasanya didefinisikan atas dasar:• energy capture / penangkapan energi (i.e.,

productivitas-yield in agriculture)• nutrient cycling / siklus nutrisi• population regulation (including food web

structure)• stability

Crop Rotation/Rotasi Tanaman

Sebelum industri agrokimia berkembang, rotasi tanaman merupakan praktik dasar/standar dalam pengendalian hama dan penyakit serta pemeliharaan kesuburan tanah.

Pengembangan pestisida dan herbisida memungkinkan praktik monokultur secara terus menerus. Jadi praktik monokultur dmkn merupakan teknik pertanian yang relatif baru.

Crop RotationShort rotations vs Long (Extended) Rotations:

Short rotation:• Usually just 2 years/ Berlangsung 2 tahun• Objective is typically pest control/Bertujuan untuk

mengendalikan hama/penyakit• Corn-soybean is the commonest crop system in the US-both

crops have a high demand. TS Jagung-Kedelai : wujud tumpangsari terpopuler di USA. Permintaan terhadap kedua komoditas tinggi

Long (extended) rotations:• 3 years or longer/ 3 tahun atau lebih• Objectives are pest control, maintain soil organic matter,

reduce agrichemical inputs/Bertujuan untuk pengendalian hama, menjaga bahan oragnik tanah, dan mengurangi penggunaan agrokimiawi

• Usually includes hay, pasture, or "green manure" to improve soil fertility. Umumnya meliputi hay, pastur, atau pupuk hijau untuk meningkatkan kesuburan tanah.

Crop RotationRotation Effect! Pengaruh rotasi tanamanThis term refers generally to the higher yields of most

crops when grown in rotation, and more specifically to the yield increases that cannot be compensated for by input substitutions.

Hal ini berkaitan dengan hasil yang lebih tinggi bagi sebagian besar tanaman ketikaditanaman secara berotasi, dan lebih khusus lag peningkatan hasil yang tidak dapat fikompensasi oleh penambahan input

Most crops produce higher yields in rotation than in continuous cultivation, usually 10-15% higher in maize (Singer & Cox, 1998).

Sebagian besar tanaman memberikan hasil lebih tinggi pada sistem rotasi dibandingkan yang tanpa rotasi (continuous cultivation). Peningkatan hasl jagung : 10 – 15% (Singer & Cox, 1998).

Intercropping• Intercropping involves growing two crops in the same

field at the same time. The following are different ways of intercropping, in order of increasing degree of association between crop components:

• Relay-intercropping-planting a second crop before harvesting the first crop.

• Strip-intercropping-growing 2 or more crops in alternating strips. Smith & Carter (1997) found that maize grown in a strip intercrop with alfalfa produced yields 6% higher in 40-ft wide strips, 11% higher in 20-ft wide strips, and 17% higher in 10-ft wide strips. May be due to extra light in border rows of maize.

• Between-row intercropping -growing 2 or more crops in alternating rows.

• Within-row intercropping -growing 2 or more crops in the same rows.

• Between-row and within-row intercrops may be either additive or replacement designs.

Intercropping Concepts.• Additive vs. replacement intercrops. In an additive

intercrop both species are planted at the same density as in their respective monoculture; in a replacement intercrop a row of one crop "replaces" a row of the second crop in forming the intercrop. Additive intercrops double the density, and therefore may use resources more completely.

Duration refers to the temporal overlap of the intercrop components:

• Differing duration-usually combines a short season crop and a long season crop. Intercrops of differing duration are usually additive.

• Similar duration-competition more intense because both components are using resources at the same time. Intercrops of similar duration tend to be replacement types.

Intercropping Concepts.

• Dominant vs. subordinate components. Typically, one crop component of the intercrop is more competitive and hence dominates the mixture in terms of growth and yield.

Dominance may be due to:• Rapid initial growth• Height• Photosynthetic pathway (C4 crops tend to

be dominant when grown with C3 crops)• Legumes are usually subordinate

Measuring Intercrop Performance• The performance of intercrops relative to

monocultures of the component crops is usually measured as Land-equivalent ratios (LER) or relative yield totals (RYT):

• Relative Yield (RY) = Yield in intercrop/Yield in monoculture

• LER = RYT = Y(i)/Y(m) = RY(1) + RY(2) + RY(3) + ....

• When LER or RYT > 1, the intercrop is said to show overyielding. That is, the intercrops are more productive than the monocultures of the components crops.

• The RYs of dominant components are often close to 1.0; efforts to increase intercrop performance often center on increasing the RY of the subordinate component.

Global Change and AgricultureGlobal warming

Evidence of global warming: • Temperature records-most of the increase

has been in night temperature• Retreat of glaciers; decreased snow and

ice cover• Measurable rise in sea level• Increased heat content of oceans• Increased plant growth (Myneni et al.

1997)

Global Change and Agriculture

The latter include: • Increased values of NDVI (normalized difference

vegetation index) detected by remote sensing• Increased biomass deposition in European forests• Increased recent tree-ring growth in Mongolia• Upward migration of plants on European

mountain tops• The increase in plant growth is likely due to

longer growing seasons; high latitude winter temperatures increased up to 4 C in the winter.

• Nicholls (1997) attributes 30-50% of the increased wheat yield in Australia since 1952 to decreased frequency of frost.

Global Change and Agriculture

Presumed causes of global warming: • Greenhouse gases-CO2, CH4, N20 (nitrous

oxide), CFCs (chloroflurocarbons)• Land-use changes. • Deforestation• Increased fire frequencyThat greenhouse gases have caused global

warming as not been "proved", there are still valid disagreements.

Global Change and Agriculture

Robinson et al. (1998, unpublished paper privately distributed) dispute that any global warming has occurred in response to increased CO2. It is accurate to say that there is currently a strong concensus among scientists that changes in atmospheric chemistry are affecting climate in predictable and understandable ways.

Global Change and Agriculture

Effects of [CO2] on Plant Growth• Gross photosynthesis increases and

photorespiration decreases.• Stomatal resistance increases (stomates close

partially in response to increased [CO2]), transpiration therefore decreases, and water-use efficiency increases (since stomatal closure affects transpiration rates more than CO2 uptake rates).

• C3 vs C4 plants: Growth of C3 plants would be enhanced more than that of C4 plants

Global Change and Agriculture

Interactions need to be considered:• [CO2] and other resources. For example, if

N is limiting, increased [CO2] may not increase crop growth.

• [CO2] and environmental influences (especially temperature).

Global Change and AgricultureAffects of Global Change on Agriculture• The overwhelming evidence from (short term)

experiments with increased [CO2] (either greenhouse or FACE-free atmosphere carbon dioxide enrichment-studies) is that biomass and/or seed production increases with increasing [CO2].

• These studies are almost always done with (1) no temperature increase, and (2) optimum levels of other resources, especially N and water.

• [One interesting conclusion we might draw is that much of the crop yields experienced in the past 50 years must be due to increased [CO2] and not just breeding and improved management, as usually assumed.]

Example of case

CROP ECOLOGY