Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Jens M. Vesterager, Niels E. Nielsen, Henning Høgh Jensen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Symbiotic N2-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha−1 under sole and 36 kg N ha−1 under intercropping as estimated by the 15N isotope dilution method around peak biomass production. The amount of N2-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha−1 accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied 15N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha−1. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha−1. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.
Original languageEnglish
JournalNutrient Cycling in Agroecosystems
Volume80
Issue number1
Pages (from-to)61-73
ISSN1385-1314
DOIs
Publication statusPublished - 2008
Externally publishedYes

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