Maize (Zea mays L.) crop response to phosphorus fertilization on fluvisols in Northern Ethiopia

A field experiment involving different P fertilizer rates (0, 10, 20, 30, 40, 50 and 60 kg P ha-1) was conducted to determine effect of P on maize (Zea mays L.) growth, yield, N and P uptakes and P use efficiency on Fluvisols at Birki village, northern Ethiopia using a randomized complete block design with three replications. The experiment was conducted under rain-fed condition between 10 July and 12 November 2011. Application of 30 kg P ha -1 significantly (P ≤ 0.01) increased maize grain yield, total above ground N and P uptakes, grain N and P uptakes and P harvest index. At this P level, grain yield increased by 1074 kg ha -1 (54.8%) over the control plot. Soil P at harvest has also significantly (P ≤ 0.01) increased as applied P increased from 0 to 60 kg P ha-1. Significant (P ≤ 0.05) increments were also observed on plant height, maize ear length and total above ground dry matter weight at 40 kg P ha -1 and on shoot P uptake at 30 kg P ha -1 over the control. However, no significant (P > 0.05) differences were observed on shoot dry matter weight, number of grains per ear, harvest index and shoot N uptake. Phosphorus use efficiencies of maize were also observed to decrease with increasing levels of applied P. At the optimum application rate of 30 kg P ha -1 , observed P agronomic and P utilization efficiencies of maize were 28.7 and 32.1 kg kg-1, respectively. Generally, the results of the study indicated that application of P fertilizer significantly increased the grain yield of maize mainly through its positive effects on the crop‘s growth parameters, yield components and total plant N and P uptakes. The analysis of marginal rate of return has further confirmed that application of 30 kg P ha-1 gave the highest net return of 3717.4 Birr ($203) ha-1which implies that it can be recommended for the production of economically optimal maize yield on Fluvisols under the environment prevailing in the study areas.