MAXIMIZING YIELD AND NET RETURNS TO NITROGEN, PHOSPHORUS AND POTASSIUM FERTILIZER APPLICATION IN RICE (Oryza sativa. L) PRODUCTION ON LOWLAND SOILS

MAXIMIZING YIELD AND NET RETURNS TO NITROGEN, PHOSPHORUS AND POTASSIUM FERTILIZER APPLICATION IN RICE (Oryza sativa. L) PRODUCTION ON LOWLAND SOILS

Abstract:

Rice (Oryza sativa .L) is an important staple and source of income for farmers in Nigeria. Current fertilizer recommendations for rice do not commonly consider fertilizer cost relative to paddy price (CP). The rates needed for maximizing yield rather than profits have been rather estimated. As the cost of fertilizer increases relative to the price of paddy, the nutrient rate needed to maximize net returns, typically called the economically optimal rate (EOR), is expected to decrease. To this end, fertilizer trials were conducted at Wushishi in Niger state and Kadawa in Kano state in 2015 cropping season to: quantify the yield response of lowland rice to nitrogen, phosphorus and potassium applications; estimate the EOR at different CP; evaluate the components of Nitrogen Use Efficiency (NUE). The trials consisted of different rates of N (0, 40, 80, 120, 160 kg/ha), P (0, 7.5, 15, 22.5 kg/ha) and K (0, 10, 20, 30 kg/ha) arranged in an incomplete factorial combination and laid out in a randomized complete block design with three replicates. At plot level, paddy yield and components of yield were measured. Mean yield without nitrogen in Kadawa and Wushishi were 2.6 and 5.05 tons/ha respectively. There were significant increases in yield with N application in both locations. Paddy yield was increased by 3 tons/ha in Wushishi with the application of 80 kg/ha of N. Similarly, 40 kg/ha produced maximum paddy yield of 3.55 tons/ha in Kadawa. Estimated optimum nitrogen rates from asymptotic non-linear regression model were 114kg/ha and 106kg/ha for Wushishi and Kadawa respectively. As the CP increased, the range of profitability and EOR decreased. In Kadawa, EOR ranged from 61 to 32 kg ha-1 of N at CP of 2 to 10. Values for EOR were 82 to 49 kg/ha for CP of 2 to 10 for Wushishi. Yield was not significantly increased with P and K applications in both locations. Agronomic Efficiency (AE) and Partial Factor Productivity decreased with increasing N rate in both locations. In Wushishi, AE and PFP at CP of 2 were 32.6 kg/kg and 95.6 kg/kg respectively. Similarly, AE and PFP at CP of 2 in Kadawa were 15.1 kg/kg and 59.6 kg/kg respectively. Nitrogen fertilization was observed to be more profitable in Wushishi due to greater crop response. Applying Nitrogen at economically optimal rate can help reduce expenditure on fertilizer while maximizing profits for rice growers. Environmental pollutions commonly associated with nitrogen fertilization can also be reduced.

MAXIMIZING YIELD AND NET RETURNS TO NITROGEN, PHOSPHORUS AND POTASSIUM FERTILIZER APPLICATION IN RICE (Oryza sativa. L) PRODUCTION ON LOWLAND SOILS