Farming and Agricultural Systems. Thomas G Chastain CROP 200 Crop Ecology and Morphology

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1 Thomas G Chastain CROP 200 Crop Ecology and Morphology

2 Several levels of ecological integration are components of the agricultural hierarchy. Starting with the individual plant, these levels increase in numbers of individuals and complexity, with the greatest complexity and numbers of individuals present in the agricultural system. Agricultural System Farming System Cropping System Community Population Plant The Agricultural Hierarchy

3 Plant Characteristics: (a) Growth and development of individual plants (b) Reproductive capacity (fertility and fecundity) (c) Plant yield components Yield basis: Yield per plant Young mustard plant (TG Chastain photo)

4 Population Refers to individuals of a single crop species (stand). Characteristics: (a) Density (b) Growth and development of the stand (c) Intra-specific competition (d) Reproductive capacity Yield Basis: Field or unit area Sunflower population (TG Chastain photo)

5 Community Community is one or more populations of cohabitating crop plants, weeds, beneficial and pest animals. Characteristics: (a) Species diversity (b) Interference and interspecific competition (c) Complementation and Niche Yield Basis: Field or unit area Corn field a community (TG Chastain photo)

6 Cropping System Cropping system = crop production system. The cropping system is the crop or pasture community, together with management practices such as tillage methods and rotations. Contour strip-cropping of alfalfa and corn (USDA photo)

7 Farming System The principle crops and management practices employed on a particular farm. Characteristics: (a) Productivity the efficiency of input utilization relative to the economic yield per unit land area. (b) Stability is the degree of variation in yield over years as affected by weather, diseases, etc. (c) Sustainability refers to the ability of yield to be maintained over an extended period. Yield Basis: Farm

8 Agricultural System Also known as agricultural ecosystems - the geographical organization of farming systems within a region having similar farming practices, climate, crops, transportation systems, economics, etc. The Willamette Valley is a temperate agricultural system specializing in seed production of grasses, forage legumes, sugarbeet, vegetables, and flowers. Characteristics: Stability, diversity, risk Yield Basis: Region Corvallis Portland Salem Willamette Valley (NASS photo)

9 Daily photosynthesis, respiration (g plant -1 d -1 ) Farming and Agricultural Systems Production is the amount of energy or material formed by an individual, population, or community. Primary production production by green plants Secondary production production by herbivores, carnivores, detritus feeders, etc. Net production production after respiration losses are accounted for. Time from emergence (days) Photosynthesis and respiration in potato (Connor et al., 2011)

10 Plant Weight Farming and Agricultural Systems Crop Growth Rate (CGR) is an index of crop growth. Can be used to indicate the change in crop growth over time on an individual plant basis, for a population of plants, or for a community. CGR = dw dt Where: CGR = crop growth rate dw = change in plant weight dt = change in time Time Record Rates of Production in Selected Crops Crop Type CGR (lbs/acre/day) Sugarbeet C3 276 Potato C3 205 Corn C4 464

11 Leaf area - an estimate of the size of the photosynthetic system the plant s biological solar energy collector. Leaf area index (LAI) is an index of the size of the photosynthetic system. LAI can be determined by using a leaf area meter, by tracing leaves on graph paper and determining the area, or by tracing the leaves on paper and by weighing the paper need to know the area:weight relationship. LAI = Where: LAI = 2.4 = LA GA LAI = Leaf area index LA = Leaf area GA = Ground area 1.2 m m 2

12 Crop Growth Rate (g m -2 day- 1 ) Farming and Agricultural Systems Crop growth rate is directly affected by light interception by the crop. The canopy is the three-dimensional arrangement of the crop s foliage stems and leaves deployed in a manner that optimizes light interception. The architecture of the canopy - the deployment of the stems and leaves, can determine crop yield Light Interception (%) Pumpkin crop canopy (USDA photo)

13 Solar Radiation Interception(%) Farming and Agricultural Systems Light interception increases with increasing LAI until the soybean crop canopy reaches an LAI of about 3. Further increases in LAI above 3 do not result in greater interception of light by the canopy. Radiation attenuation within the crop canopy (from top of the canopy to bottom) reduces the photosynthetic rates of leaves lower in the canopy at high LAI Leaf Area Index (Shibles and Weber, 1965)

14 With increasing LAI, the rate of CO 2 fixation by photosynthesis increases for both wheat and alfalfa (King and Evans, 1967). Note that there is an optimum LAI for both crops above which there is no increase in photosynthesis.

15 Net Assimilation Rate (NAR) is an indirect measurement of net photosynthetic activity. This is based on the principle that the increase in dry weight of plants in a given period is a measure of net photosynthesis. A crop, composed of a population of plants or a community, is a more efficient collector of solar energy than a single plant. At optimum plant population density and with a closed canopy, photosynthesis and conversion of photosynthetic products to yield is greatest. NAR = CGR LAI Where: NAR = Net Assimilation Rate LAI = Leaf area index CGR = Crop Growth Rate

16 If the size of the photosynthetic system is known (LAI), then the net rate of photosynthesis per unit of photosynthetic size can be estimated (NAR). NAR varies among crop species, seasonally, and with changes in the availability of solar radiation.