Abstract:
Low soil fertility is a prominent factor for low agricultural productivity, whereby inorganic fertilizers have become important inputs to overcome the problem. In Ethiopia, different blended fertilizer types are used without clearly identifying the production limiting nutrient of a specific crop for a specific soil type. The present study was designed to identify the most yield limiting nutrients for sorghum on Leptosols through nutrient omission trials, which was conducted in 2021 at two locations of Chiro district using randomized complete block design with treatments of NPKSZnB (All), All-B, All-Zn, All-S, All-K, All-P, All-N, NP, NPS, and Control (CONT), using Dibaba sorghum variety. Data on growth parameters, yield, and yield related components were gathered and analyzed. The results showed that omitted nutrients had a significant effect on leaf area (LA), plant height (PH), head weight (HW), above ground biomass (BM), grain yield (GY), harvest index (HI), nutrient uptake (NU), agronomic efficiency (AE) and apparent recovery efficiency (ARE). Accordingly, the highest mean values of the respective parameters, namely: LA (3440 cm2 ) from all nutrients applied treatment (All), PH (297cm) from NPS, HW (6.6 kg plot – 1 ) and GY (4456 kg ha – 1 ) from All, BM (13.2 tons ha – 1 ) from All-Zn and HI (40.5%) from All-K, were obtained. Furthermore, the highest mean values of NU of N (88.5 kg ha – 1 ), P (12.85 kg ha – 1 ), K (94.9 kg ha – 1 ), S (7 kg ha – 1 ), were obtained from All and the highest NU of Zn (0.59 kg ha – 1 ) was from All-K and that of B (0.12 kg ha – 1 ) was obtained from All-S treatment plot. The highest mean AE in kg of grain kg – 1 nutrient applied: N (33) from All, P (27), K (26), S (144), Zn (223) and B (1507) was recorded on All-N treatment plot. The highest mean value recordings of ARE in kg of nutrient uptaken kg – 1 of nutrient applied: N (1.09), P (0.15), S (0.28) and Zn (0.007) were detected on All and that of K (0.31) on All-N treatment plots. The highest grain (37%) and biomass (16%) yield limits were observed from nitrogen omitted sorghum. The grain yield limiting potential of the nutrients was in the order of N > P > S > Zn > B > K and that of biomass in the order of N > K > P > B > S. The maximum rate of return (1113%) was recorded on the all nutrients applied treatment (All). The omission of N, S, and Zn decreased the rate of return below an acceptable value (100%). Conclusively, the application of NPSZn could be a better alternative for sorghum grain production on Leptosols of the present study area. Moreover, comprehensive soil characterization that enables reliable identification of the soil type and production limiting nutrients, seems to be necessary for nutrient rate determination and sound recommendation of the identified limiting nutrients, in order to maximize crop productivity on a specific soil type.
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