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Biomass and nitrogen accumulation by green manure legumes as affected by phosphate rock in submerged soils

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http://www.academicjournals.org/ajar/contents/2007cont/Jan.htm
 
Title Biomass and nitrogen accumulation by green manure legumes as affected by phosphate rock in submerged soils
 
Creator Somado, E A
Sahrawat, K L
 
Subject Soil Science
Fertilizer Appications
 
Description Lowlands in West Africa are increasingly absorbing the growing pressure on land for food crop
production. However, the current intensification of lowland cropping systems result in the mining of
soil nutrient reserves, particularly of nitrogen (N) and phosphorus (P). While N can be supplied via
biological N fixation (BNF) by legumes, P deficiency frequently limits both food crop growth as well as
legume BNF, especially on acidic soils in the humid forest and savanna regions. Fortunately, large
deposits of phosphate rocks (PR) exist in many African countries; and moreover, the PR efficacy can be
enhanced when applied to submerged acidic soils. Thus the use of PR may not only supply the limiting
P to soil and food crops, but also stimulate BNF-N by legumes including legumes used for green
manuring in production systems. A screen house experiment was conducted to evaluate the effect of
PR-P on the performance of N-fixing legume Aeschynomene afraspera L. during three successive
15
cropping cycles under submerged conditions. BNF was estimated by the N-isotope dilution technique,
using rice (Oryza sativa L.) as a non-fixing plant. The experimental soil was Ultisol low in available P.
-1
Unprocessed PR from Mali was applied at 60 kg P ha . Initial application of PR significantly increased
legume above ground biomass and BNF over the unfertilized control by 1.4- and 3-fold respectively.
This PR-induced growth stimulation further increased during the subsequent cropping period with a
-1 -1
maximum biomass of 6.4 tons ha and 80 kg of BNF-derived N ha above the unamended control. The
application of P significantly increased the percent N derived from the atmosphere (% Ndfa). However,
compared to the first two cropping cycles, the efficacy of applied PR-P declined during the third
cropping cycle, probably as a result of rise in soil pH following soil reduction. The results suggest that
PR can be a useful P source for food crops in rotation with legumes.
 
Publisher Academic Publishers
 
Date 2007
 
Type Article
PeerReviewed
 
Format application/pdf
 
Language en
 
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Identifier http://oar.icrisat.org/3988/1/AfrJouOfAgriRes_2__1_1-6_2007.pdf
Somado, E A and Sahrawat, K L (2007) Biomass and nitrogen accumulation by green manure legumes as affected by phosphate rock in submerged soils. African Journal of Agricultural Research, 2 (1). pp. 1-6. ISSN 1991-637X