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Search results on 12/18/18
1688. Douglas, C.L.. 1983. Silicic acid and oxidizable carbon movement in a Walla Walla silt loam.. Ph.D Thesis, Oregon State Univ., Corvallis, OR. 75pp..
This study shows that use of ammonia fertilizers over the past 40 yrs, and particularly anhydrous ammonia in the past 15, has resulted in a more acid plow layer. The decrease in pH has caused soluble silica to leach out of the plow layer and led to cementation of the plow pan layer below 15 cm. The result is reduced water infiltration, increased water runoff and soil erosion, and increased soil water evaporation. Corrective applications of hydrated lime are explored. T: Mean silicic acid concentration in leachates from 15 cm soil layers as affected by long term N treatments. Long-term N and residue management effects on soluble carbon movement in four 15 cm layers. Soil pH and carbon addition effects on silicic acid concentration and transfer from the 0-15 cm layer.
5659. Rasmussen, P.E. and C.R. Rohde. 1989. Soil acidification from ammonium-nitrogen fertilization in moldboard plow and stubble-mulch wheat-fallow tillage.. Soil Sci. Soc. Am. J. 53(1):119-122..
Change in soil pH in relation to applied N was determined for one conventional and two stubble-mulch tillage treatments. Acidifying effects were concentrated in the top 7 cm of the stubble-mulched soil, but distributed to 22 cm or more with moldboard plowing. The rate of pH decline was greater for moldboard plowing than stubble-mulching. T: Long-term N fertilization effect on pH in the upper 45 cm of soil under different tillage systems. Linear relationship between applied N and soil pH, as affected by tillage.
7057. Van Doren, G.S.. 1983. The form and distribution of soil phosphorus as affected by management and soil variability.. M.S. Thesis, Dept. of Agronomy and Soils, WSU, Pullman, WA.
Studies were initiated in the Pacific Northwest to determine long-term effects of cropping systems and tillage management practices on the form and distribution of soil phosphorus. Studies indicated that, in comparison with the native Palouse prairie, organic phosphorus in Palouse soils has declined more than 50% with cultivation and cropping. Stratification of phosphorus, with increasing concentration towards the soil surface, was found in no-till soil. A cropped soil which has been managed without utilizing chemical fertilizer showed total and organic phosphorus accumulations in the upper 30 cm of the soil profile with depletions lower in the profile. This was not evident in the adjacent, conventionally farmed soil. However, soil varibility often masked the effects of soil and crop management on phosphorus forms and distribution in soil. For example, soil series induced wider variation (significant at the 0.01 level) in phosphorus values than did management in a study which included detailed soil mapping. This study demonstrated that many experiments are not designed to quantify variations in soils; in fact, some are designed to mask soil differences by statictical analysis. Sequential testing is suggested as an appropriate experimental design to quantify soil variability.