Some recent ideas on fertilizer response curves

In field trials in 1959-63, the sugar yield-response curves for sugar beet given 0-250 kg N/ha consisted of a steeply rising linear portion and a linear portion in which sugar yield did not change or decreased slowly, even though yield of tops and roots continued to increase. In similar trials with barley, wheat and potatoes given N and potatoes given P and K, similar response curves were obtained, but in some cases the 2nd part of the curve showed a rapid yield decrease with high N. RESP-6529