Evaluation of Nitrate sources and irrigation intervals in Onion production under biomass transfer and basin irrigation

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Kasama, Amedeus
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Leguminous tree leaf litter has potential as a nutrient source for smallholder vegetable production systems. However, quality of the leaf litter influences yield responses by the crops grown. A field experiment was conducted at Msekera Research Station in Eastern Province of Zambia to assess the effect of biomass transfer on soil nitrate availability and water use in onion production under basin irrigation using fresh Gliricidia sepium biomass (3.7%N) and Leucaena leucocephala biomass (4.2%N). Results showed that residual soil nitrate after harvest was significantly different among the treatments [no fertilization, Leucaena leucocephala biomass, Gliricidia sepium biomass and inorganic fertilizer]. Treatments under inorganic fertilizer application had the highest residual soil nitrate accumulation. Among 3, 5 and 7 days irrigation intervals, ‘5 days irrigation interval’ resulted in highest soil nitrate concentration and onion fresh yield. Inorganic fertilizer and Gliricidia sepium biomass resulted in highest onion fresh yield class with yields of 23.69 and 23.42 tons/ha, respectively. Leucaena leucocephala biomass provided a higher onion fresh yield of 21.13 tons/ha than control (no fertilization) which provided 17.53 tons/ha. The total seasonal amount of water irrigated to both main and sub-treatments was not significantly different. Five days irrigation interval was determined to be the optimal irrigation interval with water application rate of 213,843Litres/ha on loamy sand soil (FAO: Ferric Lixisols). There is need for further research to study optimal biomass decomposition periods for various Agroforestry trees before planting any crop and sensitize farmers on optimal water application intervals for onion production.
Onion growing , Soil Fertility