Evaluation of SUBSTOR-Potato model under different irrigation and fertilizer-nitrogen regimes
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Date
2011
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Punjab Agricultural University, Ludhiana
Abstract
Proper irrigation and fertilization practices are widely needed to improve water productivity, N use efficiency and to reduce the ground water depletion and contamination to groundwater. Crop simulation models provide an alternative, less time-consuming and inexpensive means of determining the optimum crop N and irrigation requirements. This study includes the evaluation of SUBSTOR-Potato model to analyze potato yield responses to water- and N-application for optimizing crop productivity under water limitations in a semi-arid irrigated environment. The treatments included combinations of three irrigation regimes- IW: PAN-E ratio of 2.0 (I1), 1.4 (I2) and 0.8 (I3) and four N rates- 0 (N0), 135 (N1), 180 (N2) and 225 (N3) kg ha-1. Evaluation analysis showed that performance of the model was reasonable as indicated by close agreement of simulated crop phenology, biomass, LAI, water use, soil water storage, tuber yield and N uptake with measured data. The normalized root mean square errors ranged between 10 and 20 % for most of the parameters. Using long term weather data, cumulative probability distribution of simulated tuber yield and ET showed that irrigation effects were greater under fertilized conditions. Scenario analysis also suggested that tuber yield and ET productivity were greater on sandy loam than loamy sand soil for comparable irrigation and N rates. Influence of initial soil water status on tuber yield was greater with increasing N rate. The ET productivity increased with increase in irrigation under low initial soil water status; whereas it increased to a point under high soil water status. Initial soil mineral-N influenced the amount of fertilizer N and post sown irrigation regime to realize a given tuber yield.