Impact of differences in the soil environment on the effect of phosphorus and potassium placement
Abstract
Greater recovery of added nutrients may occur if fertilizer is placed in a limited volume of soil, rather than mixed with all of the soil in the top 20 to 25 cm of the profile. The effect of placement has been not only reported in field and laboratory studies, but also accurately predicted with a mechanistic model. The objective of this investigation was to further explore the role of the soil chemical and physical environments that ultimately govern the effectiveness of phosphorus, P, and potassium, K, placement. In the first of three studies, data--obtained from previous research in which the changes, after P addition, of both soil solution P and P adsorbed on the solid phase were characterized for 33 soils--were used to perform a sensitivity analysis with a mechanistic model. Results indicated that the curvilinear increase of solution P with P addition is the reason for differences among soils in the effect of volume placement of P. In the second study, seven rates of K were applied to the 33 soils. After 21 days of incubation, soil solution K and exchangeable K were measured for each treatment. A greater proportion of added K remained in solution after each incremental addition, relative to the proportion of added P that remained in solution in the previous study with these 33 soils. Hence, the curvilinearity of the relation was less for K, which suggests that the effect of K placement will be less significant than that of P. In the third study, soil temperature, water content, and corn root growth were measured for three years in both a ridge till-plant and conventional tillage system. Significant differences in soil temperature and water content influenced root distributions. Root densities were higher in the row and midrow of the ridge till plots; whereas in conventional plots, root densities were highest in the row and decreased to the midrow. Since placement of P or K in the soil volume having the greatest root length density will increase recovery of the added nutrients, placement should vary with tillage practice.
Degree
Ph.D.
Advisors
Barber, Purdue University.
Subject Area
Agronomy
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