Border Effects in a Long-Term Fertility Experiment
1976
MacDonald, G. E. | Peck, N. H.
The concept of plot border effects in a fertility experiment is well known. However, the magnitude of the possible border effects is often unappreciated. Thus an experiment was designed to determine how much horizontal movement of soil across plot boundaries results from normal tillage operations. Horizontal movement of P and K was determined by soil tests at the completion of a 10-year fertility experiment during which 9 applications of differential rates of broadcast concentrated superphosphate (CSP) and potassium chloride (KCl) had been applied. Soil tests revealed that soil P was depleted to a distance of 2.7 m in the high CSP residual plots and moved into the low residual CSP plots 1.8 m. Soil K was depleted to a distance of 2.7 m in the high KCl residual plots and moved into the low KCl residual plots 2.7 m. Normal tillage operations moved soil in both directions across plot boundaries. The high CSP or KCl plots were depleted of fertility to about the same distance that the low CSP or KCl plots increased in fertility. The effective length of plots was reduced from 15 to 10 m for CSP plots and 9 m for KCl plots in the direction of the tillage operations after a period of 10 years. Dimension of long-term fertilizer plots should be adjusted according to the number of years the experiment will be continued.
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