Abstract
Winter flooding of harvested rice fields attracts migratory waterfowl and may assist in degrading rice straw residue. Field studies were conducted between 2003 and 2005 in Stoneville, MS to evaluate the impacts of winter flooding of harvested rice fields on rice straw degradation, winter weeds, soybean yield, and soil biochemical and chemical properties. The experimental area each year consisted of a harvested rice field that remained no-till after harvest and that was dissected into 7.6- by 15-m bays with constructed levees to accommodate winter flooding treatments. Flooding treatments (10-cm depth) consisted of: 1) flooded from mid-October to early March; 2) flooded mid-October to early January; 3) flooded mid-December to early March; 4) flooded mid-December to mid-January; and 5) no flood. Winter weeds were counted, biomass determined as well as residual rice straw before flooding and in early April of each year. Winter flooding reduced rice straw biomass 32% to 60% compared to 21% to 31% reduction for no winter flood with the longest flood duration resulting in the greatest loss of carbon and nitrogen from straw residues in both years. Winter flooding treatments reduced weed populations and weed biomass from 43% to 99% when compared to no flooding treatment. Soybean yields ranged from 3295 kg.ha-1 with the longest winter flooding regime to 4295 kg.ha-1 with no flooding. Significant reductions in soil nitrate levels were most consistent in the upper 0 to 2.5-cm surface soil. Soil enzymatic activity (dehydrogenase and fluorescein diacetate hydrolysis) was increased by flooding in 2003, while minimal effects were found in the second year consistent with more anaerobic conditions attained in 2003 compared to 2004. Environmental benefits of accelerated straw decomposition and weed control is achieved by winter flooding; however, there are negative consequences of nitrogen losses and reduced soybean yield.
Highlights
Rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.] are commonly grown in rotation with one another in the lower Mississippi River Alluvial Flood Plain of Arkansas (AR), Louisiana (LA), and Mississippi (MS), USA (United States of America)
Field studies were conducted between 2003 and 2005 in Stoneville, MS to evaluate the impacts of winter flooding of harvested rice fields on rice straw degradation, winter weeds, soybean yield, and soil biochemical and chemical properties
The experimental area each year consisted of a harvested rice field that remained no-till after harvest and that was dissected into 7.6- by 15-m bays with constructed levees to accommodate winter flooding treatments
Summary
Rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.] are commonly grown in rotation with one another in the lower Mississippi River Alluvial Flood Plain of Arkansas (AR), Louisiana (LA), and Mississippi (MS), USA (United States of America). Rice and soybean are commonly grown in rotation because of both crops’ adaptability to the clay soils of the midsouthern USA region. Grain yields and net returns for both crops are increased when rice and soybean are grown in rotation [1]. An alternative production practice in the midsouthern USA is to flood harvested rice fields in the late fall or early winter months (October to December) to provide wetland habitat for migratory waterfowl [2] and to enhance rice straw degradation so that the following soybean crop can be planted into minimal rice straw residue. Soybean emergence and plant fresh weight can be reduced by rice straw residues
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