Abstract
Rice yields in Uganda are still low due to poor rice production methods on smallholder farms in particular poor nursery and nitrogen fertilizer management practices. The study was set up to investigate the effect of nitrogen (N) fertilizer, nursery management and age of seedlings at transplanting on the yield of four rice cultivars (WITA 9, GSR 007, K 85 and K 5) in eastern Uganda. The nursery experiment was established with five treatments: 1) control (no chemical + transplanting 30-day old seedling), 2) di-ammonium phosphate (DAP) + fungicide + transplanting 14-day old seedlings, 3) DAP + transplanting 14-day old seedlings, 4) DAP + transplanting 30-day seedlings and 5) fungicide + transplanting 30-day old seedlings. Effect of split application of N on yield, was studied with urea (46% N) as the fertilizer source using a split-plot design with control (no fertilizer added) and 23 and 46 kg N ha-1 applied either basally or in two splits. Applying fertilizer in the nursery and transplanting 14-day old seedlings increased yields by 23-30% relative to the control, while using 30-day old seedlings did not result in any yield gain irrespective of the treatment. Splitting N applications increased yields by 0.1-0.3 t ha-1 and increased agronomic efficiency marginally. Applying 23 kg of N in two splits gave the highest return over fertilizer cost (US$ 855/ha). This demonstrates that lowland rice production in Uganda can be increased by a combination of nutrient management in the nursery, transplanting young seedlings and splitting applications of nitrogen fertilizer and represents a simple and economical option for farmers to increase rice yields. This is especially important considering that fertilizer use among smallholder farmers is restricted by high prices and limited availability. Improving N- and nursery management has great prospects for increasing rice yields on all cultivars in smallholder farms at minimal costs.
Highlights
Rice (Oryza sativa L.) is an important food and cash crop in Uganda
The higher yields could have been caused by the high rate of DAP used (50 g/m2) compared to that used by Rajagopahan and Krishnarajan 1987 and others (50 kg/ha)
The current findings show that the problem of poor nursery management which has been cited by Balasubramanian et al (2007), and Kijima et al (2010) as one of the factors contributing to low yields at smallholder farms can be managed
Summary
Rice (Oryza sativa L.) is an important food and cash crop in Uganda. The major rice growing areas in Uganda include the districts of Pallisa, Butalejja, Iganga, Bugiri (eastern Uganda), Lira (northern Uganda) and Bundibujjo (southern Uganda) (Hainesh et al, 2013). Rice production has increased in the recent past from 72,000 ha producing 109,000 t in 2000 to 92,960 ha producing 260,786 t in 2018 (FAOSTAT, 2020). Despite the increase in rice production, rice yields are still low in the lowland rice ecosystem averaging 1.5 t ha-1. One of the reasons for the low rice yields is that many farmers cultivate the crop without applying appropriate production and management practices (Balasubramanian et al, 2007). The majority of the farmers practice continuous rice cropping without fertilizer application leading to soil nutrient mining (Sanchez, 2002). Farmers who practice transplanting utilize old seedlings from poorly managed nurseries (Kijima et al, 2010) where they do not apply either manure or organic fertilizers thereby reducing the yield potential. Hainesh et al (2013) found that only few farmers use inorganic fertilizers and other jas.ccsenet.org
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