Abstract

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Highland soils are mostly Vertisols which is characterized by low content of nitrogen and are generally waterlogged due to abundant rainfall. With this view a field study was conducted at Ambo Agriculture Research Center experimental site during the main cropping season of 2013-2014, with the aim to determine the effects of drain depth on root depth (RD), yield and yield components of maize grown on Vertisols and to identify appropriate nitrogen source and time of application for maize production. The treatment was arranged factorial with five drain depths (0, 15, 30, 45 and 60 cm), two nitrogen (N) sources (urea and ammonium sulfate) and two timings of N applications (twice and thrice). The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. The results revealed that drain depths, 45 and 60 cm deep resulted in deeper root system and higher grain and stover yield than drain depths of 0, 15 and 30 cm. Grain and stover yields, 1000 grain weight and harvest index (HI) were highly significantly (P ≤ 0.05) affected by drain depths, nitrogen sources and time of application, and the interaction effect of drain depths and N source. The maximum grain yield (6.33 t ha^-1), stover yield (7.57 t ha^-1), 1000 grains weight (423.83 g) and HI(44.80%) were obtained from drain depth of 60 cm coupled with thrice split application of ammonium sulfate(AS). However, the above yields are on par with 45 cm deep drain. Similarly, thrice split application of N source gave better grain and stover yields, 1000 grain weight and HI than twice at 45 and 60 cm drain depths and the lowest were obtained from undrained plots (0 cm). Hence, drain depth of 45 cm coupled with ammonium sulfate and thrice split application could enhance maize production on Vertisols in Ambo and similar areas.

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