Soil nitrate dynamics in relation to nitrogen source and landscape position in Malawi

Phiri, R H and Snapp, S and Kanyama-Phiri, G Y (1999) Soil nitrate dynamics in relation to nitrogen source and landscape position in Malawi. Agroforestry Systems, 47 (1-3). pp. 253-262. ISSN 0167-4366

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Abstract

Nitrogen is normally the nutrient most limiting production of maize (Zea mays) — the main staple food crop — in southern Africa. We conducted a field study to determine the effect of N sources on soil nitrate dynamics at three landscape positions in farmers' fields in southern Malawi. The landscape positions were dambo valley or bottomland, dambo margin, and steep slopes. The N sources were calcium ammonium nitrate fertilizer applied at 120 kg N ha−1, biomass from Sesbania sesban, and no added N. Sesbania biomass was produced in situ in the previous season from sesbania relay cropped with maize. Nitrate in the topsoil (0 to 15 cm depth) increased to 85 days after maize planting (mean = 48 kg N ha−1) and then decreased markedly. Application of N fertilizer and sesbania biomass increased soil nitrate, and nitrate-N in topsoil correlated positively with amount of incorporated sesbania biomass. The strongest correlation between sesbania biomass added before maize planting and topsoil nitrate was observed at 85 days after maize planting. This suggests that the sesbania biomass (mean N content = 2.3%) mineralized slowly. Inorganic N accumulated in the subsoil at the end of the maize cropping season when N fertilizer and sesbania were applied. This study demonstrated the challenges associated with moderate quality organic N sources produced in smallholder farmer's fields. Soil nitrate levels indicated that N was released by sesbania residues in the first year of incorporation, but relay cropping of sesbania with maize may need to be supplemented with appropriately timed application of N fertilizer

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Uncontrolled Keywords:	Inorganic nitrogen; N input; N mineralization; relay intercrop; Sesbania sesban
Subjects:	Others > Soil Science
Depositing User:	Ms K Syamalamba
Date Deposited:	25 Jan 2013 08:30
Last Modified:	20 Sep 2013 12:32
URI:	http://oar.icrisat.org/id/eprint/6470
Official URL:	http://dx.doi.org/10.1023/A:1006279817228
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	UNSPECIFIED
Links:	Google Scholar

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