Advances in Agriculture and Agricultural Sciences

Advances in Agriculture and Agricultural Sciences ISSN 2381-3911 Vol. 4 (3), pp. 001-008, March, 2018. © International Scholars Journals

Full Length Research Paper

Nitrogen budgets in crop sequences with or without phosphorus-fertilised cowpea in the maize-based cropping systems of semi-arid eastern Africa

J. M. Vesterager, N. E. Nielsen and H. Høgh-Jensen*

Department of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen, Højbakkegaard Alle 9, DK-2630 Taastrup, Denmark.

Accepted 16 January, 2018

Abstract

Advantages of cowpea were tested in terms of net N-input by cowpea mono- or intercropped with maize in a crop sequence where sparingly soluble P sources were added to the first year crop. The grain yield of maize grown after cowpea monocrop was doubled and the N uptake increased by 60% compared to maize following maize. The N-value of growing cowpea monocropped prior to maize monocrop was equivalent to the application of 50 kg N ha^-1 as mineral fertiliser. When maize followed a maize-cowpea intercrop, grain yield was increased by 67%. Around 34% of the N contained in cowpea residues was recovered in the following maize as estimated by ¹⁵N. There was however no benefit on the second season maize of applying sparingly soluble P sources to the first season legume.

Key words: Cowpea, crop sequences, maize, nitrogen budgets, sparingly soluble phosphorus.