Effects of limestone, Minjingu phosphate rock and green manure application on improvement of acid soils in Tonga Butare, Rwanda
Loading...
Date
2003
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
A study was conducted under pot and field conditions to assess the effects of
limestone, Minjingu Phosphate Rock (MPR) and green manures (GMs) on maize
yield, soil properties and nutrient uptake. The treatments tested in the greenhouse
experiment were four rates of limestone applied either alone or in combination with
MPR and/or green manures. In the field experiment, 13 treatments were tested
namely an absolute control, recommended rate of NPK and burned lime, NP and
limestone, combinations of any two of the following materials: limestone, MPR,
Tithonia GM, Tephrosia GM, and combinations of three of these amendments. Soil
analysis at the beginning of the experiment revealed that the soil was deficient in N,
P, and K, had low levels of Ca and Mg and toxic levels of exchangeable AI.
Application of GMs improved the supply of N and K appreciably while limestone
played a great role in reducing exchangeable AI. A significant contribution of P was
from MPR. A combination of MPR, GMs and limestone supplied ample amounts of
N, P, K, Ca, Mg and reduced exchangeable AI and hence resulted into high yield.
However, high rates of limestone decreased DM yield and nutrient uptake in the
treatment with three amendments. A significant increase in DM yield was obtained in
pots, which received a combination of low rate of limestone (1/4 of the lime
requirement), MPR and GMs. In general Tithonia application gave higher yields than
Tephrosia. These results were consistent with the higher quality of Tithonia biomass
relative to Tephrosia biomass. The green manures in combination with MPR
increased P uptake significantly. Nutrient concentration data from both field and pot
experiments indicated serious deficiencies of P, K and N consistent with soil analysis data but Ca, Mg, Zn and Cu were in the sufficiency range. Furthermore, the results
indicated that using a combination of moderate rates of limestone, MPR and GMs is
the best strategy in improving acid soils in Tonga, Rwanda.
Description
Thesis
Keywords
Limestone, Minjingu Phosphate Rock, Green manure, Acid soils, Tonga Butare, Rwanda