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CSM-CROPGRO-Cotton Model under DSSAT V 4.0.2.0 has been extensively tested and validated in many studies, mainly in United States. The objective of this study was to test and validate this model in three cotton growing regions of Pakistan (Faisalabad, Multan and Sahiwal) for dynamic simulation of development, growth and seed cotton yield of four cotton cultivars (CIM-496, CIM-506, NIAB-111 and SLH-284) at varying nitrogen increments (50, 100, 150 and 200 kg ha-1) sown at different timings (20 May and 10 June). The model was first calibrated with data (phenology, biomass, LAI, and yield components) collected during 2009 at all locations against the best performing treatment May 15 sowing, cv. CIM-496 and 200 kg N ha-1 (D1V1N4) in field trials. The model was then tested with data recorded against remaining thirty-one treatments for all locations. Similarly, the data of year 2010 was used for validation. The simulated values of crop phenology (days to anthesis and maturity) by the model were reliable with the recorded data, with root mean square error (RMSE) less than 2 days during both years. Although RMSE values for LAI approached higher than 1 in many of the treatments, these values for total dry matter and seed-cotton yield were reasonably good (367 to 497 kg ha-1and 122 to 227 kg ha-1, respectively). There is a dire need to assess impact of climate variation on seed cotton yield under various climatic regions of Pakistan to ensure fiber quality and yield in future. [ABSTRACT FROM AUTHOR]

Sunflower (Helianthus annuus L.) is the leading non-conventional oilseed crop in Pakistan. Nitrogen fertilizer can affect plant growth and productivity by changing canopy size which has an effect on the radiation use efficiency (RUE) of the crop. The response of sunflower hybrids in terms of phenology, fraction of intercepted radiation (F i ), and RUE to nitrogenous rates (0, 60, 120, 180, and 240 kg ha -1 ) was studied in three field experiments conducted in three various environments: Multan (arid), Faisalabad (semi-arid), and Gujranwala (sub-humid) during spring seasons 2008 and 2009. The treatments were laid out according to a randomized complete block design with split plot arrangements, keeping the sunflower hybrids in main plots and nitrogen rates in sub-plots, and replicated three times. The results showed Hysun-38 took a maximum number of days to anthesis (101) as compared to Pioneer-64A93 (100) and Hysun-33 (99). The mean values of F i were 0.850, 0.903, and 0.978, and the estimated values of RUE for total aboveground dry matter were 2.14, 2.47, and 2.65 g MJ -1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The values of RUE for grain yield (RUE GY ) were 0.78, 0.98, and 1.26 g MJ -1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The average RUE GY values over three locations were 2.61, 2.60, 2.43, and 2.36 g MJ -2 in N 4 (180 kg ha -1 ), N 5 (240 kg ha -1 ), N 3 (120 kg ha -1 ), and N 2 (60 kg ha -1 ) treatments, respectively. Increasing rates of N increased RUE GY over the standard treatment N 3 (120 kg N ha -1 ); however, the averaged values over three locations were 1.22, 1.08, 0.99, and 0.92 g MJ -2 in N 4 , N 5 , N 3 , and N 2 treatments, respectively. Therefore, optimum water and N doses are important for attaining higher RUE, which may enhance sunflower growth and yield.

Crop nutrient management is an essential component of any cropping system. With increasing concerns over environmental protection, improvement in fertilizer use efficiencies has become a prime goal in global agriculture system. Phosphorus (P) is one of the most important nutrients, and strategies are required to optimize its use in important arable crops like cotton (Gossypium hirsutum L.) that has great significance. Sustainable P use in crop production could significantly avoid environmental hazards resulting from over-P fertilization. Crop growth modeling has emerged as an effective tool to assess and predict the optimal nutrient requirements for different crops. In present study, Decision Support System for Agro-technology Transfer (DSSAT) sub-model CSM-CROPGRO-Cotton-P was evaluated to estimate the observed and simulated P use in two cotton cultivars grown at three P application rates under the semi-arid climate of southern Punjab, Pakistan. The results revealed that both the cultivars performed best at medium rate of P application (57 kg ha -1 ) in terms of days to anthesis, days to maturity, seed cotton yield, total dry matter production, and harvest index during 2013 and 2014. Cultivar FH-142 performed better than MNH-886 in terms of different yield components. There was a good agreement between observed and simulated days to anthesis (0 to 1 day), days to maturity (0 to 2 days), seed cotton yield, total dry matter, and harvest index with an error of -4.4 to 15%, 12-7.5%, and 13-9.5% in MNH-886 and for FH-142, 4-16%, 19-11%, and 16-8.3% for growing years 2013 and 2014, respectively. CROPGRO-Cotton-P would be a useful tool to forecast cotton yield under different levels of P in cotton production system of the semi-arid climate of Southern Punjab.