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Sunday, January 21, 2018

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651. Bakken, L.R., T. Borresen and A. Njos. 1987. Effect of soil compaction by tractor traffic on soil structure, denitrification, and yield of wheat.s. J. of Soil Sci., 38:541-552.
Tractor traffic on wet soil reduced the pore volume, doubled the percentage of large aggregates (>20mm), reduced the wheat yield by about 25%, and increased the N-loss through denitrification by a factor of 3-4. None of these parameters was affected by tractor traffic at low soil moisture content. The weight of the tractor did not significantly alter the effect of compaction on the measured parameters.

3210. Bhatti, A.U.. 1990. Spatial variability and geostatistical estimation of soil properties and wheat yield on eroded lands in the Palouse region.. Chpt. 3, PhD. Dissertation, Dept. of Agronomy & Soils, Washington State Univ., Pullman, WA 99164.
Spatial variability of organic matter, soil P, and wheat yields was studied using classical statistical and geostatistical approaches on two commercial wheat farms in the Palouse region of eastern Washington. Geostatistics indicated strong spatial relationship of soil properties and wheat yields with a range of influence of 50-200 m. The two sites differed greatly in spatial patterns due primarily to differences in topography and the extent of erosion and topsoil loss. As a consequence of topsoil loss and reductions in organic matter, it was demonstrated that spatial patterns in yield and soil phosphorus were strongly correlated with organic matter patterns. Remote sensing of soil organic matter and the use of geostatistics offers a way to quickly assess spatial patterns in grain yield and available phosphorus.

3220. Bhatti, A.U.. 1990. A comparison of criteria for dividing eroded wheat fields into different management zones.. Chpt. 2 PhD. Dissertation, Dept. of Agronomy & Soils, Washington State univ., Pullman, WA 99164.
The study examined possible criteria for dividing dryland grain fields into management units for variable fertilizer (and other input) management. Criteria evaluated included fertility status, organic matter content, available water content, soil pH, erosion class, and wheat yield. Erosion class and soil pH were not satisfactory, but the other criteria were acceptable since they all allowed division of the field into three zones with significantly different grain yields as well as different nitrogen fertilizer rates (ranging from 0 to 90 kg N/ha). For each criterion, the field-averaged rates of recommended N were about 35 kg/ha, which is much lower than the grower's typical uniform application of 73 kg N/ha. Generally, the lowest N rates were recommended for eroded hilltops where productivity was low. The two best criteria appeared to be soil organic matter content and grain yield, as they accounted for P deficiency in the eroded zones. Remote sensing can now assess spatial patterns of organic matter on bare soil, thus providing a quick and easy way to delineate production zones.

4510. Miller, P.R., W.L. Graves, and W.A. Williams. 1989. Covercrops for California agriculture.. Publication 21471, Div. of Agriculture and Nat. Res..
The potential use of cover crops in annual and perennial cropping systems in CA is described. The booklet includes annual and perennial legumes, cereals, crucifers, grasses, and mixtures. Data illustrating the benefit of cover crops on infiltration and soil organic matter are presented. Selection of proper crops is described. Seeding recommendations are presented.

5715. Rasmussen, P.E., R.R. Allmaras, C.R. Rohde and N.C. Roager, Jr.. 1980. Crop residue influences on soil carbon and nitrogen in a wheat-fallow system.. Soil Sci. Soc. Am. J. 44(3):596-600.
Seven crop residue treatments were initiated in 1931 to measure long-term residue managements effects on soil organic matter in a wheat-fallow cropping system on Pacific Northwest semiarid soils. Organic carbon and total N were measured at approximately 11-yr intervals over a 45-yr period to determine residue effects on the rate of change in soil OM content. Only the addition of 22.4 metric tons of manure/ha to straw residue before incorporating prevented a decline in soil N and C. The addition of 45 or 90 kg fertilizer N or of 22.4 metric tons of pea vines/ha to straw residue before incorporation reduced N and C loss when compared to straw only incorporation. Burning of straw in the fall following wheat harvest accelerated the loss of N, but not C. Burning of straw in the spring just prior to tillage had no effect on N or C loss.

5872. Rickman, R.W. and B.L. Klepper. 1980. Wet season aeration problems beneath surface mulches in dryland winter wheat production.. Agron. J., 72:733-736.
Wet season aeration problems beneath surface mulches in dryland winter wheat production. Dentrification was a suspected cause of localized poor growth in winter wheat fields in the Northwest. Measurable anaerobic conditions occurred above and in restricting layers of slowly draining soils supporting poor growth but not in adjacent, unlayered soils supporting good growth. Surface mulch increased water infilitration in both soils but prolonged low oxygen levels in slowly draining soils. Beneath the mulch essentially all of the fertilizer N was lost on the slowly draining soil and yield was 35% lower than that on mulched normal soil.

10287. Bhatti, A.U., D.J. Mulla, and B.E. Frazier. 1991. Estimation of soil properties and wheat yields on complex eroded hills using geostatistics and thematic mapper images.. Remote Sensing Environ. 37:181-191.
Spatial variability of organic carbon, soil P, and wheat yields was measured in eastern Washington using classical statistics and geostatistics. Organic carbon content was estimated from Landsat Thematic Mapper images. Goestatistics revealed strong spatial correlations relative to classical statistics. The spatial patterns were associated with changes in surface organic matter content across the landscape resulting from extensive erosion.

10662. Ridley, A.M., W.J. Slattery, K.R. Helyar, and A. Cowling. 1990. The importance of the carbon cycle to acidification of a grazed annual pasture.. Austral. J. Expt. Agric. 30:529-537.
Soil samples were collected to a depth of 60 cm from a 73 year old experiment in Victoria, comparing an unfertilized field to two fertilized fields (4.5 t/ha superphosphate), one of which had also received lime. The soil pH of the fertilized field had declined relative to the unfertilized to a depth of at least 30 cm, while liming appeared to negate the acidification adequately. Carbon and nitrogen cycle acidification accounted for 65 and 35%, respectively, of the net acid addition on the fertilized field.

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