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Download or read book Estimating a Vailability of Nitrogen from Green Manure to Subsequent Maize Crops Using a Buried Bag Technique written by R. J. Carsky and published by . This book was released on 1989 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of leguminous green manures can reduce the consumption of fossil fuel-intensive N fertilizer and/or increase crop yields where N fertilizer is not available. A method to screen legumes for their ability to supply N to succeeding crops is needed. Ideally, the method would also have application in estimating the N supplyng capacity of soils. A buried bag field incubation technique was proposed as a simple, labor-saving method to estimate N release from soil and green manure. A test of the buried bag technique and a fallow soil sampling procedure was conducted over two maize cropping seasons on a Typic Haplustox in central Brazil. Nine legume treatments containing from 70 to 305 KG N ha-1 and C/N from 15 to 24 were incorporated into the soil followed by either maize (Zea mays L.) or bare fallow. Low density polyethylene bags (0.1mm thick) were partly filled with soil from the plow layer at 42 and 237 days after incorporation and buried until harvest of the respective maize crops. Accumulation of N in the aboveground portion of maize was closely related to accumulation of nitrate in bare fallow plots to 180 cm depth (y=10+0.69x, r2=0.895) and to the sum of initial fallow profile N plus N accumulation in bags (y=34+0.48x, r2=0.924) over two crops. The buried bag technique involved much less labor than the fallow soil method. More reliable estimates of N release were obtained with buried bag incubation during the rainy season when nitrate leaching losses in the fallow plots were considerable. When the potential N mineralization rate as measured in fallow soil exceeded 1Kg ha-1 day-1, mineralization in the bags was reduced probably by restricted flow of O2 across the plastic. The bags were shown to limit mineralization in suplemenal experiments. Most previous authors did not report decreased N release in plastic bags but mineralization rates were lower than in this study. The total N applied as green manure explained 77% of the variability in aboveground N of the first maize crop after incorporation. The fraction of applied N which mineralized was related to C/N of the legume material (y=1.6-0.05x, r2=0.65). Maize grain dry matter was significantly correlated to aboveground N contet (r2=0.92). The buried bag technique should be considered as a method of estimating N release from soil and manure.