Development of crop water stress index of wheat crop for scheduling irrigation using infrared thermometry

This study was conducted to develop the relationship between canopy-air temperature difference and vapour pressure deficit for no stress condition of wheat crop (baseline equations), which was used to quantify crop water stress index (CWSI) to schedule irrigation in winter wheat crop (Triticum aestivum L.). The randomized block design (RBD) was used to design the experimental layout with five levels of irrigation treatments based on the percentage depletion of available soil water (ASW) in the root zone. The maximum allowable depletion (MAD) of the available soil water (ASW) of 10, 40 and 60 per cent, fully wetted (no stress) and no irrigation (fully stressed) were maintained in the crop experiments. The lower (non-stressed) and upper (fully stressed) baselines were determined empirically from the canopy and ambient air temperature data obtained using infrared thermometry and vapour pressure deficit (VPD) under fully watered and maximum water stress crop, respectively. The canopy-air temperature difference and VPD resulted linear relationships and the slope (m) and intercept (c) for lower baseline of pre-heading and post-heading stages of wheat crop were found m =  -1.7466, c =  -1.2646 and m =  -1.1141, c =  -2.0827, respectively. The CWSI was determined by using the developed empirical equations for three irrigation schedules of different MAD of ASW. The established CWSI values can be used for monitoring plant water status and planning irrigation scheduling for wheat crop.Canopy-air temperature difference Infrared thermometry Crop water stress index (CWSI) Irrigation scheduling

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Not AvailableThis paper compares the composite and distributed curve number (CN) techniques in computation of runoff from a hypothetical watershed of 100×100 cells and from a natural medium-sized agricultural Tarafeni watershed located in West Bengal, India. To this end, remote sensing (RS) satellite digital data from 1989 and 2000 were used for land use and land cover classification using a maximum likelihood classifier algorithm of supervised classification for CN-generation. Runoff was estimated for each grid by using a distributed-CN approach and averaged for the whole watershed by using a weighted-runoff approach. The estimated runoff values were compared with those from the traditional composite-CN technique. In both cases of initial abstraction (Ia) taken as 0.2 S and 0.3 S (where S is the potential maximum retention), the estimated runoff caused by distributed CN technique was more than that caused by the composite-CN approach. The difference in runoff values was more for Ia=0.3S than that for Ia=0.2S; runoff caused by distributed CN with Ia=0.2S matched more closely with the observed. Furthermore, the difference was very high for small events, moderate for medium, and low for high rainfall events; it was very high for the watershed exhibiting greater CN variation.Not Availabl

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Not AvailableRice (Oryza sativa L.)–wheat (Trititicum aestivum L.) system (RWS) in South Asia is under stress, as nutrient removals by crops are higher than their replenishment through fertilizers. We evaluated improved nutrient management strategies at 10 different locations across the Indo-Gangetic Plains (IGP) of India and adjacent regions during 2003–04 to 2005–06, and compared the improved practices in terms of yield gain, nutrient use efficiency and economic returns, with existing farmers fertilizer practices (FFP), and state recommended fertilizer rates by the government departments (SR). Improved N–P–K application rates were calculated by accounting for the indigenous nutrient supply (INS), yield target and crop nutrient demand as a function of the interactions between N, P and K. Compared with the SR and FFP, improved practices increased average grain yield from 0.32 to 3.03 t ha 1 and 1.37–3.69 t ha 1 in rice, and 0.49–1.17 t ha 1 and 0.71–2.26 t ha 1 in wheat across the locations, respectively. Added net return (in US $) from improved practices over FFP and SR under RWS ranged from 219.6 to 804.9 and from 104.3 to 599 ha 1, respectively. Compared to improved practices, PFPN under SR and FFP were lower by 18.9 and 38.3% in rice, and 18.5 and 39.5% in wheat, respectively. Omission of P and K from improved nutrient management schedule resulted in yield loss of 0.6–2.8 t ha 1 in rice, and 0.43–1.84 t ha 1 in wheat, respectively. The annual removal of native P and K in the respective omission plots ranged from 21.8 to 46.1 kg P ha 1 and from 158.4 to 349.1 kg K ha 1. Application of 26 kg P and 99 kg K ha 1 under improved practices had synergistic effect on nutrient use efficiencies viz. PFPN, AEP, AEK, REP and REK. Results suggested that optimised nutrient supplies considering crop nutrient needs and INS have potential for improving yields, nutrient use efficiency and profits in RWS. The improved nutrient management strategy used in this study could be used in larger domains for improving cereal productivity, nutrient use efficiency and farm profits.Not Availabl