Abstract
Six experiments with date palm (Phoenix sylvestris Roxb.) were conducted at Bangladesh Sugarcrop Research Institute Farm, Ishurdi, Pabna during 2013-16 to assess the individual and interaction effects of organic manure (OM) supplemented from cow dung, NPK fertilizers and irrigation (December to March) on the yields of juice and goor and juice quality. The first trial examined N, P and K fertilizers consisted each of three levels and assigned in a RCBD with three replications. Based on these results, this experiment was repeated in the following year by including one more level each of N and P, and dropping one level K as followed in the first trial. The third experiment tested the effect of irrigation applied in three installments with 11 irrigation levels viz. 0, 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 liters (l) of water/plant/month in a RCBD with four replications and this experiment was repeated in the next year having eight irrigation levels applied in the same installments @ 0, 400, 450, 500, 550, 600, 650 and 700 l of water/plant/month depending on the results of preceding year to more precisely trace the effect of irrigation. The fifth experiment investigated four levels of OM and NPK fertilizers in another RCBD with four replications. In the last trial, NPK fertilizers, OM and irrigation each with three levels were taken from accounting of the results of the earlier experiments in order to arrive at final conclusion. The data collection was made on juice and goor yields as obtained from individual plants on the basis of cuts given throughout the tapping period. As quality parameters, pH, brix (%), pol (%), purity and reducing sugar (RS) of juice were determined at the same period on weekly basis. The results revealed that the individual and combined applications of NPK fertilizers exhibited significant impacts on different parameters under study. Among the three nutrient elements, N and K had more pronounced effects than P in respect of yield and qualitative parameters. The highest juice yield was harvested by applying the combination of NPK @ 1800 g, 300 g and 1400 g/plant but the highest goor yield was processed from the NPK combination of 1200 g, 200 g and 1400 g/plant due to having higher brix reading in this combination. Irrigation had significant effects on several yield attributes under study except the pH of juice. Irrigation level of 600 l of water/plant/month gave the highest value of both juice and goor yields whereby goor yield increasing rate was measured the highest in this level. OM had significant effect on juice and goor yields, purity and RS content but produced no effect on pH, brix and pol. The combination of 45 kg of OM and NPK fertilizers@ 1200 g, 200 g, 1400 g/plant was superior to any other fertilizer combination with respect to economic return. For interactions of the three tested nutrients, combination of NPK and OM or NPK and irrigation were superior regarding the yield and quality parameters except pH. Juice and goor yields increased significantly due to the combination of the three nutrient elements and the highest juice yield was obtained from the highest levels (45 kg OM/plant, NPK @ 1800 g:300 g:1400 g/plant and 600 l of water/plant/month) but the highest goor yield was achieved with the combination of 45 kg OM/plant, NPK @ 1200 g:200 g:1400 g/plant and 600 l of water/plant/month due to having higher brix. The latter treatment combination, having the highest values each of goor yield, gross return, gross margin and BCR with less variable cost, could be considered as the best package practice for successful date palm cultivation for tapping purpose.