EFFECT OF SPLIT NITROGEN APPLICATION ON USE EFFICIENCY AND YIELD OF RICE (Oryza sativa) UNDER IRRIGATION AND RAIN-FED CONDITIONS

Abstract

Many researchers have studied the effects of split nitrogen fertilizer application in crop production. However, there is little available information on number of splits of the same total quantity of nitrogen that needs to be used in rice production. Two field experiments were conducted at the research fields of the Savannah Agricultural Research Institute (SARI), in Nyankpala, near Tamale in the Tolon District of Northern Region of Ghana, during the 2013 rainy season, and in the dry season of the year 2014. The specific objectives were to determine which split pattern of the nitrogen fertilizer will result in its efficient utilization by the rice in terms of growth, secondly which nitrogen split regimes will give maximum yield of rice and also to determine the nitrogen effect on the nutrient quality of rice. The experiments were laid out in a split plot design. Ten treatments were replicated four times for the rain-fed study and three times for the dry season experiment that was carried out under irrigation. The experiments consist of two factors: rice varieties Jasmine 85 and Digang as the main plot treatment and levels of nitrogen top dressing as the sub plot treatment. NPK rate of 90 - 60 - 60 kg ha-1 were used for the two experiments and the types of fertilizers used were NPK (15, 15, 15) and Sulfan (24 % nitrogen). The sub plots treatments consisted of control (no fertilizer application) (Tl)60 kgha-1ofNPK (T2), 60 kg ha-1 ofNPK + 30 kg halof N (T3), 60 kg ha-1 ofNPK + 15 + 15 kg ha" ofN (T4) and 60 kg ha' ofNPK + 10 + 10 + 10 kg ha-1ofN (Ts). Splitting-N into two application affected plant height and tillering ability at all the growth stages for the rain-fed experiment, this also applied to the irrigation experiment except the maturity stage of tillers which was not significant. Splitting-N into two applications influenced yield of rice varieties significantly, with Jasmine 85 recording 6.9 ton ha-I and 4.6 ton ha-' for rain-fed and irrigation studies respectively. Digang variety recorded 6.1 ton ha-I and 3.4 ton ha-I for the rain-fed and irrigation respectively. Jasmine 85 was more efficient in N utilization than Digang. The presences of phosphorus and potassium also enhanced nitrogen utilization. Agronomic efficiency of applied N was effective under the rain-fed. Crop recovery efficiency and physiological efficiency of applied N were effective with N-split into two. In conclusion, the rain-fed and irrigation experiments followed similar trend from the analysis of plant height, tiller counts, yield and N use efficiency. NPK rate of 90 kg ha-I ofN + 60 kg ha-I of P + 60 kg ha-I of K and the 30 kg ha-I of N been split into two recorded the maximum yield. The two split of N also gave the highest N content in the grain. Jasmine 85 is more efficient in N utilization and yield than Digang.