Assessing the effect of irrigation water management strategies on napier production

Abstract

Complexity of crop responses to water has led to exploration of empirical crop production functions in yield estimations. There is paucity of information on Napier production response to different irrigation water management strategies. The main objective of the study was to assess the suitability of using biophysical models in predicting fodder yield responses to different irrigation water management strategies as a contribution to sustainable intensification on fodder production in Uganda. Specifically, this study aimed at assessing soil moisture variations due to different irrigation levels under Napier production. Secondly, to determine the response of Napier dry matter (DM) yields (ton/ha) to different irrigation regimes. Lastly, to predict Napier yield response under rainfed, full irrigation, and deficit irrigation using DSSAT-CANEGRO model. The study area was located at Mbarara Zonal Agricultural Research Development Institute (MbaZARDI)). Experimental data for three growth cycles on canopy cover (%), DM yields, irrigation amounts (mm) and soil characteristics were utilized in model calibration and validation. Results indicated that nearly 80% of the sensitive parameters were observed to be related to growth and the rest to phenology. PARCEMAX which accounted for about 78% of DM yield variability had the highest sensitive index. TDELAY emerged with a sensitivity index of 0.64 on canopy height. Based on calibrated model performance, predicted and measured values were in accord with a root mean square error (RMSE) of 10.314 ton/ha, coefficient of determination (R2) of 0.76 and Wilmott agreement (d-index) of 0.764. Potential Napier DM yields at harvest were underestimated in the range of 2.33 - 5.94%. Under predicted Napier DM yields ranged between 10.97 – 38.76 ton/ha whereas canopy height ranged between 1.92 –2.86 m. Under dry conditions, it is economically viable for dairy farmers to adopt ensilage of Napier at 30% DM yields (28 days after planting). Accumulated harmful nitrates during drought are also reduced through fermentation in silage. Therefore, DSSAT illustrated it’s appropriateness in pre-season decision-making on cropping patterns and irrigation management strategies.