Saturday, 15 July 2006

Cover Crop and Nitrogen Rate Management for Sustainable Production of Sweet Corn under No-Till.

Muchha R. Reddy, North Carolina Agricultural and Technical State Univ, Dept of Natural Resources and Env Design, Carver Hall 238, 1601 E Market Street, Greensboro, NC 27411, Nishantha W.A.R. Fernando, North Carolina A&T State Univ, Dept Natural Res. Env. Design, Carver Hall 224-C, 1601 E Market Street, Greensboro, NC 27411, and Carl R. Crozier, North Carolina State Univ, Soil Science Dept, Vernon James Res. and Ext. Ctr., 207 Research Station Road, Plymouth, NC 27962.

Deterioration of water quality due to agrochemicals is a major environmental issue. Use of cover crops is an important Best Management Practice (BMP) not only to reduce the inorganic N fertilizer but also to improve the soil fertility through the long-term build up of soil C pools. No-till practice coupled with cover crops provides added advantages by sequestering soil C and improving soil quality. Field experiments were conducted during the years 2003 and 2005 to evaluate the response of sweet corn to cover crop and N rate under no-till conditions. The experimental design was a split-plot with four replications. The cover and no cover crop were main plot treatments. Four N treatments (0, 56, 112, and 224 kg ha-1) under cover and no cover crop were sub plot treatments. The experiments were located at the North Carolina Agriculture and Technical State University Farm, Guilford County, NC, USA. The soil at the site was a Mecklenburg sandy loam (fine, mixed thermic Ultic Hapludalfs). The field plots were prepared and biculture of crimson clover and rye mixture was planted in early fall. The cover crop was allowed to grow till the spring of the following year. The cover crop produced adequate biomass in both the years. In 2003, cover crop was mowed with a flail mower whereas in 2005 it was rolled, and crimped in the field plots. Sweet G 90 corn was planted in the plots with no-till planter. Ammonium nitrate was used as a N source and it was banded at the specified rates in split applications in the respective plots. Results showed that the sweet corn yields were not significantly different between the cover and no cover treatments in both years. However, corn yields in 2005 seem to have been improved in cover plots as compared to no cover than it was in 2003. Differences in corn yields between cover and no cover narrowed down with the increasing N rate in 2005. In 2003, the corn yield increased up to 10 Mg ha-1 with increasing fertilizer rate up to 112 kg ha-1 N. In 2005, corn yield increased only up to 56 kg N ha-1 and no significant differences were found in the corn yields at higher N rates in cover plots. Corn yields were slightly improved with the increasing N rate in no cover plots. Shoot dry matter tended to decrease with increasing N rate. Nitrogen content of the soil and the plant tissue were not significantly different under the cover and no cover treatment and the N treatments. Mid-season chlorophyll measurements during 2005 showed slightly higher values for corn grown in no cover plots. Overall, the results of this research suggest that continuous use of cover crops has a greater potential to reduce inorganic N fertilizer application in sweet corn by 50% while improving environmental quality under the Piedmont conditions of North Carolina.

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