Effect of nitrogen fertilizer rate and Nitrapyrin on leaf chlorophyll, leaf nitrogen concentration, and yield of three irrigated maize hybrids in Nebraska (nitrogen).
Lohry, Raun David.
Thesis (Ph.D.) University of Nebraska, Lincoln, 1989. 119 pages.
1989
บทคัดย่อ
A study was conducted from 1986 through 1988 on a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustolls) using three Pioneer brand maize hybrids (3377, 3475, 3551) to examine the effects of increasing fertilizer N rates (0, 75, 150, 300 kg N ha(-1)), a nitrification inhibitor (nitrapyrin, 0 and 0.56 kg ha(-1)), and tillage on leaf N, leaf chlorophyll, dry matter production, N uptake, N leaching, and yield. To characterize the relationships of applied N and yield components, soil and plant samples were taken at about one week before and one week after anthesis. Soil samples were taken to a depth of 0.45 m and leaf N samples collected using a punch to obtain 10 mm disks from the laminar portion of the leaf. Additional soil samples to a depth of 1.8 m were taken before planting and after harvest.
Leaf disks were analyzed for chlorophyll using 80% acetone extraction and spectrophotometric colorimetry and for N concentration by modified semi-micro Kjeldahl technique. Chlorophyll and leaf N concentrations were correlated in 1987, but chlorophyll varied significantly with environmental conditions in other years. Laminar leaf punch N concentration was linearly related to midseason stover N concentration. Leaf N concentration was not consistently correlated with grain yield, although a significant association was observed in 1987. Midseason dry matter production, N uptake, and N concentration increased with applied N in every year. Grain yields were not influenced by tillage practice. Grain yields in 1986 were not increased by N applications beyond 75 kg N ha(-1) due to residual N effects. Plots incurred hail damage in 1987 but yields were better than 1986 with maximum yields (12 Mg ha(-1)) occurring near the 150 kg N ha(-1) rate. Because of heat stress, 1988 grain yields were 30% lower than 1987
, but dry matter production, N uptake, and N concentration in the stover at harvest were all increased. Grain N removal was near the amount applied at rates below 150 kg N ha(-1). Nitrapyrin decreased leaf N concentration in 1987, but did not affect yield. Nitrapyrin increased preanthesis inorganic soil N in all years. Postharvest soil samples exhibited significantly higher amounts of inorganic N at the highest N rate indicating that N not used by the crop is subject to leaching.