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Frequency of Nitrogen Fertilizer Carryover in the Humid Midwest
Author(s) -
Vanotti Matias B.,
Bundy Larry G.
Publication year - 1994
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1994.00021962008600050023x
Subject(s) - loam , agronomy , fertilizer , avena , crop , nitrogen , growing season , seeding , mathematics , nutrient , yield (engineering) , zoology , environmental science , soil water , chemistry , biology , soil science , materials science , organic chemistry , metallurgy
Soil tests for residual NO ‐ 3 can improve prediction of crop N fertilizer requirements in the humid Midwest, but their adoption as a standard procedure in fertilizer N recommendation programs depends on the frequency of significant profile NO ‐ 3 ‐N carryover. Data from a 25‐yr crop sequence experiment (1967 to 1991) on a Rozetta silt loam soil (finesilty, mixed, mesic Typic Hapludalf) at Lancaster, WI, were used to estimate the frequency and extent of N fertilizer carryover. Sequences studied included unfertilized oat ( Avena sativa L.) grown after corn ( Zea mays L.) that received a range of N rates. Oat yields were influenced by the residual effects of the previous year's N application in 21 of the 25 yr, with yield responses varying from 500 to 1500 kg ha −1 . Soil profile measurements (0 to 90 cm) taken before seeding oat in spring 1987 through 1991 showed substantial NO ‐ 3 ‐N carryover that was usually found below the 30‐cm depth. Significant increases in profile NO ‐ 3 ‐N content occurred at low N rates (56 to 112 kg N ha −1 ) in years with limited rainfall during the preceding corn growing season, but only at higher N rates under optimum corn growing conditions. Total N uptake by oat was also significantly affected by corn N treatments, and it was well correlated with profile NO ‐ 3 ‐N. A nutrient efficiency index that characterized the yield response of oat to profile NO ‐ 3 ‐N was used to estimate carryover NO ‐ 3 ‐N from 1967 to 1986 oat yield data. Expected N fertilizer carryover values ( P = 80%) ranged from 32 to 106 for a 168 kg N ha −1 rate, and from 63 to 151 kg NO ‐ 3 ‐N for a 224 kg N ha −1 rate. The wide variation of expected amounts of N carryover reflects typical year‐to‐year changes in conditions affecting N recovery by corn and retention by soil. Results of this study indicate that significant residual profile NO ‐ 3 ‐N occurs in most years on well‐drained silt loam soils in Wisconsin, and that year‐specific tests for profile NO ‐ 3 ‐N are needed to adjust N recommendations for varying amounts of NO ‐ 3 ‐N carryover.