First-year nutrient availability from injected dairy manure
1989
Motavalli, P.P. | Kelling K.A. | Converse, J.C.
Estimates of N, P, and K availability to corn (Zea mays L.) from injected dairy manure on three field sites in south central Wisconsin were make using a fertilizer equivalence approach. Nutrient uptake from treatments of a control, three rates of manure (approx. 53, 97, and 138 Mg ha-1 yr-1 on a wet basis), and three rates of broadcast fertilizer were evaluated. Crop nutrient recoveries of fertilizer N, P, and K were generally higher than crop recoveries of manure total N, P, and K. Estimates of first year N, P, and K availability showed substantial variability across rate, location, and year with standard deviations oftern about 50% of the mean. Ranges for N, P, or K availability were 12 to 63, 12 to 89, and 24 to 153%, respectively. These data do not identify those factors responsible for differences in nutrient availability from one site-year to another. Biological or chemical availability indices of a 1-wk anaerobic incubation at 40 degrees C or a 16-h autoclaving in 0.01 M CaCl2 solution were evaluated as measures of N availability and compared with field results. Correlations between measured changes in NH4-N from these indices, as well as total Kjeldahl N and inorganic N levels in the top 30 cm of soil 4 to 6 wk after treatment application, and N uptake indicated inoganic N levels to be a better index of N availability than the other indices examined. However, to determine nutrient availability on a routine basis, more reliable biological or chemical indices are necessary. A simple model may help to simulate environmental effects and the contribution of residual nutrients in the soil.
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