MANAGEMENT OF LABLAB PURPUREUS L. RESIDUES IN COTTON-BASED FARMING SYSTEMS AND CONSEQUENT EFFECTS ON PROPERTIES OF A TYPIC PELLUSTERT
Mar 10, 2017

Agronomy & physiology WCRC Agro-physio-australia WCRC1
Abstract                                                                         Back to Table of contents

The effects of mulching or incorporating residues of dolichos (Lablab purpureus L.), sown in rotation with cotton (Gossypium hirsutum L.), in broad (1.5 m wide) beds on soil properties of a Vertisol was studied in Northern New South Wales, Australia. Soil was sampled from the 0-0.10 m (bed surface) and 0.20-0.30 m (below bed) depths of edges and centres of broad beds during January 1993. Soil properties monitored were particulate, mineralized and total organic matter, dispersion index, plastic limit, geometric mean diameter (GMD) of soil aggregates formed after puddling and drying at 40˚C (soil reactivity), soil aggregate density, exchangeable cations, nitrate-N and electrical conductivity of 1:5 soil:water suspension. Residue management had no significant effect on soil organic matter fractions, although coarse (2 mm - 212 µm), fine (212-53 µm) and total soil organic matter contents on bed surfaces were greater than that below beds, and coarse particulate organic matter at the edges of beds was greater than that at the centres. Compared with mulching, incorporating dolichos residues resulted in a significantly lower dispersion index. Mulching also resulted in higher values of dispersion index below beds when compared with bed surfaces. Plastic limit at the centres of beds, was significantly lower than that in the edges. Smallest GMD of soil aggregates occurred in the centre of mulched beds. Greatest values of soil aggregate density occurred at soil water contents ≤ 0.10 kg kg-1 below beds when dolichos residues were mulched. Where dolichos residues were incorporated, at soil water contents ≤ 0.10 kg kg-1 aggregate densities in the soil surface were lower in bed centres when compared with those at the edges of beds. Greatest exchangeable K, and lowest exchangeable Na and exchangeable sodium percentage (ESP) occurred where dolichos residues were incorporated. In comparison with mulching, exchangeable Mg was higher and exchangeable Ca lower below beds with residue incorporation. Nitrate-N on bed surfaces was higher than that below beds with mulching. Mulching improved only friability of surface soil in bed centres, whereas surface and sub-surface indices of soil physical and chemical fertility were improved by incorporating dolichos residues.

Conclusions

Soil reactivity in the of centre bed surfaces was the only soil property to be improved by mulching of dolichos residues whereas incorporating dolichos residues improved indices of soil quality such as aggregate stability, exchangeable cations and ESP (Doran et al., 1994) in the surface and at 0.2-0.3 m. Good soil quality can, therefore, be maintained at this site by incorporating residues of dolichos sown in rotation with cotton.

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