Modeling Sugar Beet Response to Different Combinations of On-Farm Water Management Practices Under Semi-arid Sub-tropical Environment

Crop water productivity modeling becomes a valuable tool in developing deficit irrigation strategies and optimizing agricultural water use for economical and sustainable production in arid and semi-arid regions. The objective of the current study was to test and validate the FAO-developed AquaCrop model for sugar beet under different combinations of on-farm water management practices using 2years average measured data sets collected during the 2011-2012 and 2012-2013 cropping seasons. The model was first calibrated using the data set of nine full irrigation treatments and then validated for twenty-seven deficit irrigation treatments, respectively. The model performance was evaluated using different statistical indicators, e.g., coefficient of determination (R-2), normalized root-mean-square error, degree of agreement (d(index)) and the mean bias error. The results revealed that AquaCrop was able to simulate sugar beet canopy cover fairly for all treatments. The model performance was also excellent for simulating sugar beet root yield and biomass under all no-stress and mild-stress treatments. However, the model showed poor results when moderate water stress was applied without mulching or sever stresses were applied irrespective of the mulching conditions. The results further revealed that the model overestimated the water productivity for all treatments. The AquaCrop model can thus be satisfactorily used for evaluating the effectiveness of proposed irrigation management strategies for sugar beet, however, the limitations should be kept in mind when interpreting the results in severely stressed conditions. Moreover, on the basis of the obtained results, it is strongly recommended that the sugar beet growers should raise their crop on medium raised bed covered with black film or straw mulch and should apply 20-40% deficit irrigation instead of full irrigation as this will be the most advantageous treatment in terms of improved yield and increased water productivity.