1Semalulu O and Mateete Bekunda2

1National Agricultural Research Laboratories, Kawanda, P.O. Box 7065, Kampala.

2Makerere University, Faculty of Agriculture. P.O. Box 7062, Kampala

Abstract

TWIN N is a growth enhancement product that is said to contain biologically active micro-organisms which can fix atmospheric nitrogen into plant available forms. It is said to be effective in all plants, legumes and non legumes, thus could partially reduce the need for mineral N fertilisers. This field study evaluated the growth and yield response of maize (longe V) and beans (K132) to Twin N with and without mineral fertiliser on-station and on-farm in Tororo and Mukono districts. Soils in Tororo are sandy with very low N and P while Mukono soils are clayey with low N and P. On-station treatments consisted of N at 0, 25, 50, and 100% of the recommended N rate [i.e. N0, N25, N50, N100] and P (0, 50 and 100% of the recommended P rate or P0, P50, P100), arranged in a factorial combination, replicated four times. Each treatment plot was then split into two, one half received Twin N and the other none. The experimental design was a split plot factorial with N, P treatments as the main plots while Twin N was the sub plot. On-farm treatments consisted of simplified a version those on-station. Treatments comprised of a control, Twin N, N50, (N50+Twin N), (N50+P50) and (N50+P50+Twin N). Nitrogen was applied as urea and P as SSP. Drought spells generally affected crop performance. On-station, beans grain yield was unaffected by Twin N, but decreased at 100%N (P<0.001). In plots treated with P50 and either N0 or N25, Twin N application decreased maize grain yield [3.67 vs 2.33 t ha-1 at N0 and 3.67 vs 2.00 t ha-1 for N25 (lsd=1.24, P<0.05)]. On-farm (Tororo), applying Twin N alone did not affect bean yields (454 vs 395 kg ha-1, lsd=142, NS). Applying N50 then Twin N increased bean yields but not significantly (454 vs 544 kg ha-1 P>0.10). Combining N50, P50 and Twin N gave the highest bean yields, but were not different from the control (557 vs 454 kg ha-1, P>0.10). However, yields for the N50+P50+Twin N treatment were significantly higher than Twin N alone (557 vs 395 kg ha-1, P<0.10). At Mukono, bean yields were not affected by Twin N. Applying Twin N or N50 did not increase maize yield significantly (P>0.05). Applying N50+Twin N gave the highest maize grain yield, but this was not significantly different from the control (1,960 vs 1,864 kg ha-1, lsd=160, P>0.05). Results suggest that Twin N benefits may be realised with supplemental addition of N and P fertilisers.

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