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.