Crop residue and fertiliser N effects on nitrogen fixation and yields of legume–cereal rotations and soil organic fertility

• Published in: Field crops research Vol. 83; no. 1; pp. 1 - 11
• Main Authors: Shah, Z., Shah, S.H., Peoples, M.B., Schwenke, G.D., Herridge, D.F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-06-2003; Elsevier
• Subjects: Benefits; corn; crop residues; cropping systems; crops; economic sustainability; Fertiliser N; fertilizer rates; grain yield; land productivity; Lens culinaris; mung beans; N balance; nitrogen; nitrogen content; nitrogen fertilizers; Nitrogen fixation; plows; Pulses; Residues; Rotations; shoots; Sorghum bicolor; summer; Triticum aestivum; Vigna radiata; Wheat; Zea mays; Residues; Fertiliser N; Nitrogen fixation; Benefits; Pulses; Wheat; N balance; Rotations
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/S0378-4290(03)00005-4

Improved management of nitrogen (N) in low N soils is critical for increased land productivity and economic sustainability. We report results of a rainfed rotation experiment, conducted in the Northwest Frontier Province (NWFP), Pakistan, during 1995–1999 to evaluate effects of residue retention and fertiliser N on N
2 fixation inputs and yields of a mungbean (
Vigna radiata)–wheat (
Triticum aestivum) sequence, and a lentil (
Lens culinaris)–summer cereal sequence. Mungbean and sorghum (
Sorghum bicolor) or maize (
Zea mays) were grown in the summers and lentil and wheat in the winters. Immediately after grain harvest, above-ground residues of all crops were either completely removed (−residue), or chopped into 5–20
cm pieces, spread across the plots and incorporated by chisel plough (+residue). Fertiliser N rates were nil or 120
kg
N/ha for wheat and nil or 150
kg
N/ha for sorghum/maize. The percentage of mungbean N derived from N
2 fixation (%Ndfa) ranged from 47% to almost 100% (mean of 75%). On average, mungbean fixed 112
kg
N/ha (+residues) and 74
kg
N/ha (−residues), with N balances of +64
kg
N/ha (+residues) and +9
kg
N/ha (−residues). Lentil %Ndfa ranged from 50 to 87% (mean of 73%). Values for crop N fixed were 42–85
kg
N/ha, with a mean of 68
kg
N/ha. Average N balances for lentil were +27
kg
N/ha (+residues) and +16
kg
N/ha (−residues). Grain yields of the 0N wheat responded to the previous mungbean (36% increase over the 0N sorghum), but showed an even greater response to fertiliser N applied to the previous sorghum (150% increase). Highest yields were recorded for the N-fertilised wheat (average of 2.27
t/ha). Shoot biomass yields of the 0N sorghum and maize responded strongly to the previous lentil crop (49% average increase over the 0N wheat) and fertiliser N, applied either to the crop itself (140%) or to the previous wheat crop (32%). Residue retention increased shoot biomass yields of both the summer (average of 20%) and winter crops (average of 9%). Grain yield benefits of residues were 13% for mungbean, and 8% for wheat and lentil. Soil organic N and total organic C, labile C and C management index (CMI), were all increased by N inputs, from both fertiliser and N
2 fixation, and by retention of residues We concluded that retention of residues improves the N economy of the cropping system and enhances crop productivity through the additional N and other soil effects. The question of whether farmers who traditionally remove residues for fodder and fuel would change practices and return the residues to the soil will depend to a large extent on the relative profitability of both options.