Browse on keywords: fertility tillage nitrogen
Search results on 03/25/19
690. Bear, F.E.. 1931. Soil management.. J. Wiley, N.Y..
A fairly complete text on soil management - fertility, tillage, organic matter, fertilizers; describes proper plow, moisture content, and depth to improve soil tilth; describes weeds as a potential cover crop; field study in England - free living N fixers input ~44 lb/ac/yr (est.). Azotobacter critical pH = 6.4.
1657. Doughty, J.L., F.D. Cook, and F.G. Warder. 1954. Effect of cultivation on the organic matter and nitrogen of brown soils.. Canadian J. Agr. Sci. 34:406-411.
Over 14 yr of cropping, soils lost 26% of OM and 33% of total N. Only part of the N loss is accounted for by crop removal. Some N is lost by leaching, also some gaseous loss of N other than as ammonia.
4807. Nelson, A.L.. 1950. Methods of tillage for winter wheat.. WY Agr. Expt. Sta. Bulletin 300.
Fallow/winter wheat production decreased soil N by 33% in the top 6" over 35 years. Continuous cropping lost 24% of the soil N. Crop rotations using green manure every 4th year did not decrease the loss of soil N. Average winter wheat yields (bu/ac) over 34 years for 3 rotations were: oats/rye(GM)/winter wheat/corn - 12.9; oats/peas(GM)/winter wheat/corn - 12.7; fallow/winter wheat - 13.7; oats/corn/winter wheat/rye - 13.2; oats/corn/winter wheat/peas - 14.1; oats/corn/winter wheat/fallow - 13.2. It was observed that green manure took years to break down. Tillage with an eccentric one-way increased winter wheat yields 2 bu/ac over 10 years compared to plowing. The eccentric one-way conserved moisture. Continuous cropping resulted in winter wheat yields 55% of biennial yields following fallow. Soil moisture was 3-4% lower in October after continuous cropping versus fallow.
9764. Varvel, G.E., J.L. Havlin and T.A. Peterson. 1989. Nitrogen placement for winter wheat in three fallow tillage systems.. Soil Sci. Soc. Am. J. 53:288-292.
Increased soil water storage with increasing amounts of surface residue in winter wheat-fallow cropping systems has not consistently resulted in higher grain yields in the Great Plains. Earlier results had suggested increased amount of surface residue may increase N immobilization and limit N availability, thereby reducing potential for use of the additional stored soil water. This study was conducted to determine if N placement below the zone of organic matter or surface residue accumulation would reduce N immobilization and increase yields.
10367. Rasmussen, P.E. and C.R. Rohde. 1991. Tillage, soil depth, and precipitation effects on wheat response to nitrogen.. Soil Sci. Soc. Amer. J. 55:121-124.
Wheat yield response was measured for ten crops in a wheat-fallow rotation, with N fertilizer rates ranging from 45-180 kg N/ha. Three tillages were used: moldboard plow, offset disk, and sweep. Grain yield varied with growing season precipitation (GSP). There was a trend towards higher yield with conventional tillage when GSP was above normal. The amount of N applied for optimum yield was >135 kg N/ha with above-normal GSP and <45 kg N/ha with below-normal GSP. Excess N decreased grain yield when GSP was near normal, but not when above or below. Applied N increased straw yield curvilinearly, with little influence of tillage or soil depth. Precise selection of the amount of N to apply each year was difficult because of the strong influence of GSP.