Abstract:
In semi arid areas of Tanzania, rainfed lowland rice production is constrained by
inadequate plant nutrients and soil moisture thus restricting plant growth culminating
into very low yields. With the adoption of appropriate rainwater harvesting (RWH)
technologies the soil moisture stress is significantly alleviated. A study was
conducted on the Ndala River Catchment comprised of Isulilo, Njiapanda and
Bukangilija villages in Maswa district Tanzania.The objectives were to evaluate the
fertility status of the soils and their suitability for rice production and the response of
rice (Oryza saliva L. var. Supa India) to farmyard manure (F), phosphorus (P),
nitrogen (N) and F-P-N applications over three cropping seasons (2002/03 to
2004/05) at Bukangilija village. The fertility status of the soils and their suitability
for rice production were evaluated based on the local and technical indicators of soil
fertility and land quality. Nitrogen was applied at the rate of 0, 50 and 100 kg N ha'1
as urea, phosphorus at 0, 30 and 60 kg P ha'1 as TSP and farmyard manure (kraal
manure) at 0, 3.5 and 7 t ha'1. The P and F rates were accordingly broadcasted and
incorporated into the surface soils one week before rice sowing and N was applied at
two equal splits, at tillering and panicle initiation stages. Sowing was done between
December and early January based on the long term seasonal rainfall distributions.
Based on local and technical indicators of soil fertility, the soils on the catchment
were of low fertility status and moderately suitable for rice production under RWH.
The major limitations included low total nitrogen and organic matter contents,
available zinc, soil moisture retention and high exchangeable Ca: Mg and Ca: Mg: K
ratios and high ESP. The F, P and N and F-P-N combinations significantly increasedIll
tillering, dry matter and grain yields and N, P and K contents in the rice plants and
the main effect increases were in the order N>F>P. The ranges in the number of
tillers per hill, dry matter yields, grain yields, N, P and K contents in the rice plants
between the control and the highest F-P-N combinations were 10.6, 3522 kg ha’1,
1342 kg ha'1, 25.92 g kg’1, 1.38 g kg‘'and 12.12 g kg'1 , respectively. The rice
response to F, N and F and the FPN combinations were due to increased availability
and uptake of plant nutrients particularly N, P and Zn. The long term seasonal
rainfall amounts and distribution and El-Nino-Southem Oscillation (ENSO) indices
gave good and reliable projections on the time of sowing rice seeds in the study area.
Based on the generated data farmyard manure, P and N rates at 3.5 t ha’1 30 kg P ha’1
and 50 kg N ha’1, respectively could be adopted for increased and sustainable rice
production where R.WH technologies have been adopted on the Ndala River
Catchment. Agro-climate extension service should be established.
