Effect of Sowing Season and Seeding Rate on the Morphological Traits and Yields in Pea Cultivars of Differing Leaf Types

Determination of optimal N-fertilization rates, N_OR , for crop production that minimize risk of environmental degradation require accurate application of a response model. Several models are available to describe crop yield response to N fertilization. The objective of this work was to compare the relative accuracy of a quadratic, f(N _Q), a modified Mitscherlich, and tanh( N ) models on 48 data sets. Data were collected from a Tara silt loam (fine-silty, mixed, frigid Pachic Udic Haploboroll) over a 6-year period using two maize ( Zea mays L.) hybrids and four tillage treatments, mouldboard plough, chisel plough, ridge tillage and no-tillage. In about one-third of the cases, all models performed about equally well. Generally, the tanh( N ) and modified Mitscherlich models gave better fit between N rate and grain yield data. The N_OR, ranged from about 140 to 170 kg ha^?1 for the modified Mitscherlich model, 136 to 184 kg ha^?1 for the tanh( N) function, and 124 to 173 kg ha^?1 using the f(N _Q) model. Estimated grain yields at these rates ranged between 6.58 ± 1.30 to 7.59 ± 1.69 Mg ha^?1 for the 90-day Minnesota maturity rated (MR) hybrid and between 7.52 ± 2.40 to 8.72 ± 1.70 Mg ha^?1 for the 95-day MR hybrid.