Physiological parameters affecting crop yield

full analysis of physiological crop growth parameters

1. Physiological Parameters affecting crop yield

2. Water use efficiency Water use efficiency (WUE) is the measure of a cropping system’s capacity to convert water into plant biomass or grain . Crop water use efficiency: the efficiency with which an individual crop converts water transpired (or used) to grain. Crop WUE (kg/ha/mm) = grain yield ( kg/ha) crop water supply (mm) – soil evaporation WUE can affect the yield potential of the crop. WUE is a measure of crop’s ability to extract stored moisture from the soil This is a physiological property as WUE is also a measure of plants ability to convert biomass into grain i.e. Assimilate Partitioning

3. Nutrient U se Efficiency Physiologically it is defined as the yield increase in relation to the increase in crop uptake of the nutrient in above-ground parts of the plant. It is the ability of the plant to transform nutrients acquired from the source applied into economic yield It is the ratio of total change in yield upon application of nutrient and the total amount of nutrient added Partial factor productivity (PFP) is a simple production efficiency expression which is a long term indicator of overall cropping systems ability to transform the biomass into a more economic form i.e. grain PFP can be calculated for large areas and comes under fertilizer policy issues as well

4. Assimilate Partitioning It refers to distribution of assimilates i.e. photosynthetic products to various plants parts or more technically the sinks There may be many sinks in a plant and many a times an organ may behave as a source and as a sink at various times of plant growth Biological and economic yield of "crops " can be influenced by interactions of source and sink Sink demand for assimilate (i.e ., sink strength) influences the photosynthetic rate of source leaves. Sink strength is a product of sink size and sink activity Highest yield will be obtained when there is a balance between source and sink

5. Harvest Index (HI) Harvest index is the proportion of the aboveground dry matter at physiological maturity that is allocated to the economic product (e.g., grain in maize or wheat ). It is the ratio of Economic yield to the Biological yield Maximum harvest index varies among crop species (e.g., 55% for maize hybrids vs. 20% for canola varieties), among genotypes within a crop species (e.g., 55% for North American maize hybrids, 40% for tropical maize cultivars , and 1050% for maize inbred lines), and among ‘environments’ in which it is measured (e.g ., harvest index is usually negatively affected by biotic and abiotic stresses ) Provides an indication of a crop’s ability to convert plant biomass into grain yield .

6. Harvest Index (HI ) Contd.. Fig-HI of some important crops Improving harvest index has been critical to advancing the yield potential of some important cereal crops Harvest index in grain crops is the result of partitioning of dry matter to the grain during the grain filling period, either from net canopy photosynthesis during the grain filling period or from remobilization of pre anthesis dry matter accumulation

7. Respiratory Efficiency Fig - A significant amount of the CO2 fixed by photosynthesis is respired to produce the energy needed for production of new organs and maintenance of old ones. This is often termed a “cost”. Costs associated with growth and maintenance of crops can be represented as biomass equivalents One of the physiological interventions is to reduce the respiratory losses i.e. to increase the efficiency of respiration for better yield

8. Aerobic Rice Aerobic rice is a production system where rice is grown in well-drained, non-puddled, and non-saturated soils A fundamentally different approach is to grow rice like an upland crop, such as wheat, on non flooded aerobic soils, thereby eliminating continuous seepage and percolation. This also reduces evaporation Aerobic Rice cultivars have Vigorous seedlings Rapid biomass development Deep roots Erect leaves They have a high HI even under moderate stress

9. C4 Rice This is the most ambitious project of IIRI in association with Bill and Melinda Gates foundation It basically aims at transforming the convention C3 system in rice to a Physiologically more successful C4 from Identification of most of the genes and machinery development is over and now they are heading towards transformations