Phosphorus forms and extractability from three sources in a recently exposed calcareous subsoil

Irrigation-induced erosion and land leveling have decreased crop yields on - 800 000 ha of south-central Idaho silt loam soils because of topsoil removal. Phosphorus availability is a known production problem after topsoil removal. This study evaluated the effect of three P sources on soil P solubility by three standard methods for calcareous soils. A long-term study was initiated on a Portneuf silt loam (Coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips. Phosphorus treatments applied across all strips were conventional fertilizer (applied according to soil test), dairy manure, and cheese whey. All treatments increased the freshly exposed subsoil bicarbonate extractable ortho-P concentrations up to or greater than the topsoil concentrations, which were more than adequate for economical crop production. The high-whey and manure treatments increased the subsoil saturation paste and 0.01 M CaCl2 extractable ortho-P concentrations up to or greater than the untreated topsoil ortho-P concentrations. The initial topsoil ortho-P solubility was along the ?-tricalcium phosphate (?-TCP) isotherm and the initial subsoil was well below the ?-TCP isotherm. The ortho-P solubility of the subsoil monocalcium phosphate (MCP) treatment remained just below the ?-TCP isotherm. The cottage cheese whey treatment increased subsoil P solubility up to the ?-TCP isotherm and the manure treated subsoil ortho-P solubilities were between the ?-TCP and octacalcium phosphate (OCP) isotherms. Most subsoil ortho-P concentrations by all three extraction methods decreased from spring to fall and then increased over winter in the subsequent spring samples. Soil solution ortho-P concentrations decreased with time in the subsoil treatments except immediately following treatment applications. The topsoil ortho-P extract concentrations by all three methods varied among samplings but remained about the same during the study period

Improving exposed subsoils with fertilizers and crop rotations

Irrigation-induced erosion and land leveling have decreased crop yields on approximately 800 000 ha of south-central Idaho silt loam soils. Previous attempts to increase subsoil productivity to that of the topsoil have not been successful on these soils. This study was conducted to find a method(s) for increasing the productivity of freshly exposed subsoil to that of the topsoil and to determine the factor(s) limiting subsoil production. A 4-yr study was initiated by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips of a Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid). Different crop rotations were established within the strips and fertility treatments were applied across the strips. The fertilizer treatments were conventional fertilizer application according to soil test, dairy manure, and two cottage cheese (acid) whey rates. During the fourth year, dry edible bean (Phaseolus vulgaris L., cv. Viva) were grown on the entire plot area as a test crop. The application of 44 Mg manure ha-1 in the spring and 93 Mg manure ha-1 in the fall of 1991 (first year of study) was the only treatment that restored subsoil bean production to that of the topsoil plots. Plant Zn and soil organic C concentrations were the only measured factors that correlated with bean yield increases on the subsoil

Organic phosphorus source effects on calcareous soil phosphorus and organic carbon

The loading, solubility, mobility, and plant availability of P is a growing environmental concern to regulators and planners of nutrient management plans, confined animal feeding operations, and wastewater land application permit sites. Insufficient information is available on how P reacts from different organic sources when applied to calcareous soils. A field study was conducted to determine the interactions among P application rate, source, extractability, and soil organic carbon (OC) concentration. A Portneuf silt loam (Coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids) topsoil and freshly exposed subsoil were fertilized with monocalcium phosphate (MCP), cheese whey, and dairy manure. Organic matter added with the whey did not influence soil OC concentrations whereas organic matter added with the manure doubled the subsoil OC and increased the topsoil OC concentrations. Bicarbonate and saturation paste extractable ortho- and organic-P concentrations were linearly related to soil OC concentrations but were not related to the amount of ortho- or organic-P added. All forms of P increased more per unit of added P in the order manure > whey > MCP and were correlated with the soil OC concentrations. These results suggest organic waste applications should be managed from :oil P test data rather than on P application rates

Phosphorus forms and extractability from three sources in a recently exposed calcareous subsoil

Irrigation-induced erosion and land leveling have decreased crop yields on - 800 000 ha of south-central Idaho silt loam soils because of topsoil removal. Phosphorus availability is a known production problem after topsoil removal. This study evaluated the effect of three P sources on soil P solubility by three standard methods for calcareous soils. A long-term study was initiated on a Portneuf silt loam (Coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips. Phosphorus treatments applied across all strips were conventional fertilizer (applied according to soil test), dairy manure, and cheese whey. All treatments increased the freshly exposed subsoil bicarbonate extractable ortho-P concentrations up to or greater than the topsoil concentrations, which were more than adequate for economical crop production. The high-whey and manure treatments increased the subsoil saturation paste and 0.01 M CaCl2 extractable ortho-P concentrations up to or greater than the untreated topsoil ortho-P concentrations. The initial topsoil ortho-P solubility was along the ?-tricalcium phosphate (?-TCP) isotherm and the initial subsoil was well below the ?-TCP isotherm. The ortho-P solubility of the subsoil monocalcium phosphate (MCP) treatment remained just below the ?-TCP isotherm. The cottage cheese whey treatment increased subsoil P solubility up to the ?-TCP isotherm and the manure treated subsoil ortho-P solubilities were between the ?-TCP and octacalcium phosphate (OCP) isotherms. Most subsoil ortho-P concentrations by all three extraction methods decreased from spring to fall and then increased over winter in the subsequent spring samples. Soil solution ortho-P concentrations decreased with time in the subsoil treatments except immediately following treatment applications. The topsoil ortho-P extract concentrations by all three methods varied among samplings but remained about the same during the study period

Improving exposed subsoils with fertilizers and crop rotations

Irrigation-induced erosion and land leveling have decreased crop yields on approximately 800 000 ha of south-central Idaho silt loam soils. Previous attempts to increase subsoil productivity to that of the topsoil have not been successful on these soils. This study was conducted to find a method(s) for increasing the productivity of freshly exposed subsoil to that of the topsoil and to determine the factor(s) limiting subsoil production. A 4-yr study was initiated by removing the surface 0.3 m of topsoil from strips between undisturbed topsoil strips of a Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid). Different crop rotations were established within the strips and fertility treatments were applied across the strips. The fertilizer treatments were conventional fertilizer application according to soil test, dairy manure, and two cottage cheese (acid) whey rates. During the fourth year, dry edible bean (Phaseolus vulgaris L., cv. Viva) were grown on the entire plot area as a test crop. The application of 44 Mg manure ha-1 in the spring and 93 Mg manure ha-1 in the fall of 1991 (first year of study) was the only treatment that restored subsoil bean production to that of the topsoil plots. Plant Zn and soil organic C concentrations were the only measured factors that correlated with bean yield increases on the subsoil

Organic phosphorus source effects on calcareous soil phosphorus and organic carbon

The loading, solubility, mobility, and plant availability of P is a growing environmental concern to regulators and planners of nutrient management plans, confined animal feeding operations, and wastewater land application permit sites. Insufficient information is available on how P reacts from different organic sources when applied to calcareous soils. A field study was conducted to determine the interactions among P application rate, source, extractability, and soil organic carbon (OC) concentration. A Portneuf silt loam (Coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids) topsoil and freshly exposed subsoil were fertilized with monocalcium phosphate (MCP), cheese whey, and dairy manure. Organic matter added with the whey did not influence soil OC concentrations whereas organic matter added with the manure doubled the subsoil OC and increased the topsoil OC concentrations. Bicarbonate and saturation paste extractable ortho- and organic-P concentrations were linearly related to soil OC concentrations but were not related to the amount of ortho- or organic-P added. All forms of P increased more per unit of added P in the order manure > whey > MCP and were correlated with the soil OC concentrations. These results suggest organic waste applications should be managed from :oil P test data rather than on P application rates