A Randomized complete block design was used and three wheat genotypes (Chakwal-50, Wafaq-2001 and GA-2002) were replicated four times among five planting windows denoted as PW’s. The present studies were conducted with the objectives (a) to understand wheat crop biodynamism and its relation with yield under variable climatic conditions of Pothwar, (b) to parameterize and evaluate the APSIM-wheat module under variable local environmental conditions (c) to enhance understanding about the resilience of wheat under rainfed conditions using APSIM. Field trials on wheat were performed during two wheat growing environments from 2008 to 2010 at high (Islamabad), medium (Chakwal) and low (Talagang) rainfall zones of Pothwar. Université de soutenance : University of Arid Agriculture, RawalpindiĬlimatic resilience of wheat is its capacity to absorb disorder, maintain, self-organization while retaining the same basic structure and ways of functioning, adaptating to stress and change. Increasing the potential storage capacity for remobilization is expected to increase grain yield especially under conditions of terminal drought.Titre : Climatic Resilience of Wheat (Triticum aestivum) Using Simulation Modeling in Pothwar
These factors were, little growth due to water or N deficit in the weeks prior to and shortly after anthesis (when most of the assimilates accumulate for later remobilization), poor sink demand of grains due to low grain number as a result of little pre-anthesis growth or high photosynthetic rate during grain filling. Increasing the capacity or potential to accumulate pre-grain filling assimilates for later remobilization by 20% increased yields by a maximum of 12% in moderate seasons with terminal droughts, but had little effect in poor or very good seasons in which factors that affect the amount of carbohydrates stored rather than the storage capacity itself appeared to limit grain yield. High N application often reduced the proportion of water available after anthesis and decreased the relative contribution of remobilization to grain yield as long as grain yields increased, particularly on soils with greater water-holding capacity. The simulated contribution of assimilates stored prior to grain filling to grain yield can amount to several tonnes per hectare, however, it varied substantially from 5–90% of grain yield depending on seasonal rainfall amount and distribution, N supply, crop growth and seasonal water use. Simulation results highlighted that in each of these locations assimilates stored prior to grain filling often contributed a significant proportion to grain yield.
The model, linked to long-term historical weather records was used to analyse yield benefits from assimilates stored prior to grain filling under rainfed conditions at a range of locations in the main wheat growing areas of Australia. The simulated relative contribution of assimilates stored prior to grain filling to grain yield also decreased with increasing availability of water after anthesis. Analysing system components indicated that with increasing yield, both the observed and simulated absolute amount of remobilization generally increased while the relative contribution to grain yield decreased. The field measurements allowed the routine for remobilization of assimilates stored prior to grain filling in the model to be tested for the first time and simulations showed close agreement with observed data. Model outputs were compared with detailed measurements of N fertilizer experiments on loamy soils at three locations in southern New South Wales, Australia. APSIM-Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, crop growth and development. Assimilates stored prior to grain filling have been identified as important contributors to grain yield in such environments, but quantifying their benefit has been hampered by inadequate methods and large seasonal variability. Grain yields of rainfed agriculture in Australia are often low and vary substantially from season to season.