Effect of temporary flooding on cotton growth and nitrogen nutrition in soils with different organic matter levels

A glasshouse experiment was conducted to study the effect of temporary flooding on the growth and development of cotton (Gossypium hirsutum L. cv. Deltapine 61) and the recovery of nitrogen applied as urea fertiliser in two black earths differing in organic matter content, with three water treatments. Two floodings were applied, at 15 days after planting and at 45 days. Plant dry weight and growth characteristics of the cotton plant such as height, number of leaves, leaf area and fruiting points were greatly reduced by the flooding treatments. The cotton plants were more affected by the first than the second flooding. A greater depression in the various growth characteristics was found in the high organic matter soil than the low organic matter soil. The soils behaved differently in their interaction with the water treatments. With the control water treatment, cotton grown on the high organic matter soil produced more dry matter and assimilated more nitrogen but had a lower nitrogen concentration and apparent recovery of urea nitrogen than did cotton grown on the low organic matter soil. For the flooding treatments the low organic matter soil produced more dry matter and assimilated more nitrogen, but had a lower nitrogen concentration and a higher apparent recovery of urea nitrogen than did cotton grown on the high organic matter soil. The lower apparent recovery of urea nitrogen in the high organic matter soil during temporary flooding appears due mainly to higher loss of nitrogen by denitrification, although other mechanisms may be significant. The wider implications of the results in terms of field practice with irrigated cotton are discussed