Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: May 10, 2000
Publication Date: N/A
Interpretive Summary: Nitrogen mineralization in no-till cotton systems measured in situ using undisturbed soil cores was numerically greater with a crimson clover than a rye cover crop. Heat units showed a significant correlation to N mineralization. Timing and amount of N input in no-till cotton can be bett managed when N mineralization associated with cover crop residues is considered. Development of a simple and reliable method of predicting N mineralization from readily available weather data and residue characteristics appears promising.
Technical Abstract: Crimson clover (Trifolium incarnatum L.) and winter rye (Secale cereale L.) are popular winter cover crops for cotton in the southeast Heat units can be used to predict N mineralization and determine management influences on nutrient supply. Undisturbed soil cores incubated in situ were used to measure cover crop effects on N mineralization in two no-tillage cotton- cover crop systems and the possibility of using heat units to predict N mineralization. Cotton yields (seed + lint) were 1.1 and 2.3 Mg ha-1 for 1997 and 1998. Clover and rye residue biomass were 6.2 and 11.3 Mg ha-1 in 1997 and 5.4 and 5.2 Mg ha-1 in 1998. Soil N mineralized from May through August was nearly three times greater in the cotton-crimson clover than in the cotton-rye system (two year average 65 versus 23 kg N ha-1, respectively). Nitrogen mineralization was influenced by periods of drought during both years. More N was mineralized during the first 35 d in 1998 than in 1997 (approximately 20 kg N ha-1). Soil degree days were significantly correlated with N mineralized in the crimson clover (r = 0.56, P = 0.07) and rye (r = 0.52, P= 0.09) systems. Cumulative rain for a period was not correlated with N mineralization. Further work is being conducted to evaluate the use of heat units in predicting N availability.