Experimental Agriculture



THE IMPACT OF FALLOWING AND GREEN MANURING ON SOIL CONDITIONS AND THE GROWTH OF SUGARCANE


D. J. NIXON a1a2p1 and L. P. SIMMONDS a2
a1 Mhlume (Swaziland) Sugar Company Ltd, P.O. Box 1, Mhlume, Swaziland
a2 Department of Soil Science, The University of Reading, Whiteknights Park, Reading, RG6 6DW, UK

Article author query
nixon d   [PubMed][Google Scholar] 
simmonds l   [PubMed][Google Scholar] 

Abstract

There are currently concerns within some sugar industries that long-term monoculture has led to soil degradation and consequent yield decline. An investigation was conducted in Swaziland to assess the effects of fallowing and green manuring practices, over a seven-month period, on sugarcane yields and the physical properties of a poorly draining clay soil. In the subsequent first sugarcane crop after planting, yields were improved from 129 t ha−1 under continuous sugarcane to 141–144 t ha−1 after fallowing and green manuring, but there were no significant responses in the first and second ratoon crops. Also, in the first crop after planting, root length index increased from 3.5 km m−2 under continuous sugarcane to 5.2–6.8 km m−2 after fallowing, and improved rooting was still evident in the first ratoon crop where there had been soil drying during the fallow period. Soil bulk density, total porosity and water-holding capacity were not affected by the fallowing practices. However, air-filled porosity increased from 11 % under continuous sugarcane to 16% after fallowing, and steady state ponded infiltration rates were increased from 0.61 mm h−1 to 1.34 mm h−1, but these improvements were no longer evident after a year back under sugarcane. Levels of soil organic matter were reduced in all cases, probably as a result of the tillage operations involved. In the plant crop, root length was well correlated with air-filled porosity, indicating the importance of improving belowground air supply for crop production on poorly draining clay soils.

(Accepted June 19 2003)


Correspondence:
p1 Current address: The South African Sugar Experiment Station, Private Bag X02, Mount Edgecombe 4300, South Africa. Email: david.nixon@sugar.org.za