Critical Compositional Nutrient Indexes for Sweet Corn at Early Growth Stage
2001
Khiari, Lotfi | Parent, Léon-Etienne | Tremblay, Nicolas
It would be instrumental to define nutrient norms from small-size crop databases at the V4–V6 corn (Zea mays L.) growth stage for in-season N fertilizer recommendations. Our objective was to derive Compositional Nutrient Diagnosis (CND) and Diagnosis and Recommendation Integrated System (DRIS) nutrient index ranges from a sweet corn database and to relate nutrient concentration and indexes to ear yield. A sweet corn database of 240 observations on commercial yields and N, P, K, Ca, and Mg concentrations in 30-cm high corn seedlings were divided at random between survey (n = 200) and validation (n = 40) subpopulations. The proportion of low-yield specimens in the survey population was computed at inflection point of a cubic cumulative variance ratio function and was associated with a chi-square value (CND r ²) of 3.9 that was confirmed in the validation subpopulation. Critical CND nutrient indexes were found to be symmetrical about zero as follows: −0.70 to +0.70 for N, −0.45 to +0.45 for P, −1.14 to +1.14 for K, −0.63 to +0.63 for Ca and Mg, and −1.05 to +1.05 for the residual filling value. Summing squared critical nutrient indexes also gave a CND r ² of 3.9, the minimum CND imbalance index for high-yield targets (>6.7 Mg ha⁻¹). Nutrient concentration values were little to closely related to CND indexes (R ² = 0.34–0.87). The DRIS and CND indexes were highly related to each other (R ² = 0.91–0.99). For N at V4–V6 growth stage, the CND N index was the most closely related to ear yield.
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