EKTAN INA-2

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 (SDA)SDA: Sesuatu yang sangat dibutuhkan

tanaman agar mampu tumbuh berkembang untuk menghasilkan produk pertanian (a harvestable yield).

Pada sebagian besar agro-ecosystems, produktivitas tanaman dibatasi oleh ketersediaan satu atau dua resources yang dibutuhkan, seperti: nutrisi, air, dan cahaya.

Hasil yang diperoleh tanaman merupakan fungsi dari tingkat keterbatasan SDA yang tersedia dan tingkat efisiensi tanaman dalam memanfaatkan SDA.

FAKTOR-FAKTOR LINGKUNGAN

I. CLIMATE/IKLIMBeberapa unsur iklim yang penting;

diantaranya: • Light/cahaya matahari• Temperature/suhu• Humidity/kelembaban udara• Precipitation/curah hujan• Wind/angin

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

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

humidity, wind)


II. SOILS/TANAH

1. SOIL CONSTITUENTS/KOMPOSISI TNH2. MINERAL (INORGANIC) FRACTION/FRAKSI

MINERAL3. SOIL ORGANIC MATTER/BAHAN ORGANIK4. SOIL STRUCTURE/STRUKTUR TANAH5. SOIL TYPES/JENIS TANAH6. SOIL ORGANISMS/ORGANISME DALAM TANAH7. SOIL Ph/pH tanah


III. RESOURCES/(SDA)• Light/Cahaya matahari• Carbon dioxide/CO2

• Water/Air• Nutrient/Nutrisi

CLIMATE/IKLIM

I. LIGHT (Solar Radiation = Radiasi Surya)

• Penyebaran cahaya secara musiman bergantung pada letak lintang. [How does the light environment of tropical latitudes differ from that of temperate and boreal latitudes?]

• Tumbuhan (termasuk tanaman tertentu) menunjukan tanggap fotoperiodisitas terhadap panjang hari, khususnya fenologinya.

CLIMATE/IKLIM

I. LIGHT (Solar Radiation)• Fenologi tanaman didefinisikan sebagai

tahapan perkembangan tanaman selama siklus hidupnya dan tahapan tsb dipengaruhi oleh kondisi lingkungan. (Hall, 2001); meliputi: perkecambahan, juvenil, pembungaan, bolting, pembentukan umbi dsb.

• Tanaman berhari panjang, berhari pendek, dan tanaman neutral. "Long day" (LD) plants; "short-day" (SD) plants; and "day neutral" (DN).

CLIMATE/IKLIM

II. TEMPERATURE/SUHUVariasi suhu musiman dan harian

(diurnal) meningkat sejalan dengan peningkatan garis lintang.

Suhu menurun seiring peningkatan tinggi suatu tempat.

Laju perubahan suhu karena perubahan tinggi tempat dikenal sebagai lapse rate dan laju penurunan suhu udara kering sekitas 1OC 100 m-1 dan 0,6 OC 100 m-1 untuk udara basah.

CLIMATE/iklimII. TEMPERATURE/SUHU• Sebagian besar proses=proses di dalam

tubuh tanaman memiliki suhu optimum. • Respirasi meningkat sejalan dengan

peningkatan suhu.• Perkembangan tanaman umumnya

dikendalikan oleh suhu. Satuan tanggap tanaman terhadap temperatur lingkungan biasa dikenal dengan istilah degree days –jumlah kumulatif derajat suhu di atas suhu dasar (base or threshold temperature).

• Tanaman yang tumbuh pada temperatur lebih tinggi dari temperatur normalnya akan tumbuh lebih cepat (contoh: cepat berbunga), yang dapat mengakibatkan penurunan hasil.

CLIMATE

III. PRECIPITATION

GO TO ANOTHER SLIDE :

RAINFALL N CROPPING SYSTEMS IN INDONESIA…Ю

SOILS

I. SOIL CONSTITUENTS• Atmosphere• Water• Mineral (inorganic) materials• Soil organic matter (SOM)• Soil organismsThe 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:1. Plants need anchorage, so that there

should be adequate soil layer.2. Plants need water, so that soil should

hold adequate water and supply.3. Plants need oxygen for respiration, so

that soil should be able to provide it without any interruption.

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

SOILS5. Plants need nutrients from soils, which

are absorbed by roots, so that soils should have some characteristics to supply and retain nutrients.

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.

7. Some plants through root exudates add to soil toxic chemicals (allelo-chemicals) and soil should be able to decompose them to avoid root damage.

SOILS8. 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

9. 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

SOILS

10.When both plant and animals live in soil, it should be able to maintain suitable temperatures required by those living beings

SOILSTherefore…Soils is suitable for everything at

anytime It is required to treat the soil with the

right knowledge of it in order to receive benefits the mankind wants

soil always have many associations and interactions among these factors (physical, chemical, physico-chemical and biological factors)

Physical factors

Soil textureParticle size distribution (clay, silt and

sand)In generalCoarse sand 0.25 – 2.0 mmFind sand 0.05 – 0.2 mmSilt 0.002 – 0.05 mmClay < 0.002 mm

Physical factors

Bulk density and porosityBoth factors related to:1. Capacity for gas exchange2. Root growth and penetration3. Drainage and retain water4. Infiltration and percolation

Physical factors

Soil structureComposition of pores and soil

aggregatesPores consist of :Micro pores (capillary water retained)Macro pores (gas exchange and

drainage)

Crumb structure – best for agriculture50 % each of micro and macro pores.

Physical factorsSoil water content• Saturated condition• Field capacity• Permanent wilting pointSoil temperature• Increase root growth and activities• Increase microbial population• Increase organic matter

decomposition• Increase seed germination

Chemical factorsNutrient contents in soilGas contentChemical reactions

Physico-chemical factors (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 factorsMicro and macro both fauna and floraImportant activities:• Mineralization of organic matter• Nitrogen fixation in legumes• Micorrhyza promoting P absorption• Enzymes activities and nutrient

transformation in soils• Improve porosity by earthworm

(tunneling)• Improve root absorption activities

RESOURCESLightQuantity• Full Sunlight: 200-500 Wm-2 or 1000-2000

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

m-2 s-1• Seasonality: The highest monthly (i.e.,

growing season) maximum light levels are at higher latitudes.

Crop yields in the tropics (compared to temperate zones) are ultimately limited by:

• incident radiation• cloudiness-compare wet season and dry

season yields

RESOURCES

Growth and Yield are ultimately related to light interception.

• At the leaf level: There is a minimum amount of light required for a positive net photosynthesis to occur, called the light compensation point.

• 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.

• Rates of canopy photosynthesis are usually proportional to LAI

RESOURCES

• 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.

• LAD is proportional to the total amount of light energy absorbed during the crop's growing season, and thus to yield.

RESOURCESCO2

The direct (physiological) effects of this increase in atmospheric CO2 are:

• increased rates of photosynthesis, especially in C3 plants, resulting in higher crop yields.

• increased water-use efficiency.• higher C:N ratios in plant biomass.• 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.

RESOURCES

• 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),

• Decreased specific leaf area, reducing the CO2-fertilization effect.

RESOURCES

Soil Water• Field capacity 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.

• 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.

RESOURCES

• Available water is the amount of water between field capacity and permanent wilting point.

• Soil water content is influenced by both soil texture and soil organic matter (SOM).

• Fine-textured soils have a higher total pore volume, and hence can hold more water.

• Clay particles hold water more tightly. SOM functions similar to clay particles in affecting soil water-holding capacity and soil water potential.

RESOURCESNutrition• 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.

• 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).

Nutrient cycling

Refers to the processes that transfer nutrients to and from plants and the various soil (and atmospheric) pools.

These pools can be characterized as:• active, inorganic forms and

microbial biomass-very rapid turnover;

• slow, new crop residues and coarse particulate organic matter; and

• Passive, fine particulate organic matter and humic substances-very slow turnover.

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).

That is the relationship between yield (Y) and resource supply (S) involves resource uptake (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.

Factors that influence crop yield are of several types and include:

• Resources not under grower control: light, CO2, water (precipitation), nutrients released by mineralization.

• 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).

• Resources under grower control: nutrients (from fertilizer), water (from irrigation).

Factors that influence crop yield are of several types and include:

• Environmental conditions under partial grower control: pest, weed, and pathogen populations; SOM; soil structure; soil pH.

• Crop varieties.• 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.

• Infrastructural or institutional factors: access to credit, suitable varieties, extension services, inputs, markets.

Interactions Among Species in 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.

Herbivores• 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.

Groups of herbivores:• Vertebrates-birds, mammals• Invertebrates-insects, arachnids (mites),

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

Herbivores

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

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.

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.

Pathogens

• 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.

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

Diversity has been defined as:• Richness-number of species• Equitability-number and relative abundance• Connectance or complexity-usually as food-

web complexity

Ecosystem function is usually defined in terms:• energy capture (i.e., productivity-yield

inagriculture)• nutrient cycling• population regulation (including food web

structure)• stability

Crop Rotation

Prior to development of agrichemicals, rotations were the standard practice to control pests and diseases and maintain soil fertility.

Development of pesticides and herbicides made continuous monoculture possible. Thus continuous monoculture is a relatively recent agricultural practice.

Crop RotationShort rotations vs Long (Extended) Rotations:

Short rotation:• Usually just 2 years• Objective is typically pest control• Corn-soybean is the commonest crop system

in the US-both crops have a high demandLong (extended) rotations:• 3 years or longer• Objectives are pest control, maintain soil

organic matter, reduce agrichemical inputs• Usually includes hay, pasture, or "green

manure" to improve soil fertility.

Crop Rotation

Rotation Effect!This 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.

Most crops produce higher yields in rotation than in continuous cultivation, usually 10-15% higher in maize (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.


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.


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.


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


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

EKTAN INA-2

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