Nitrogen Utilization of Corn Under Minimal Tillage and Moldboard Plow Tillage. I. Four‐Year Results Using Labeled N Fertilizer on an Atlantic Coastal Plain Soil¹

Abstract

Crop responses and N uptake of corn (Zea maysL.) grown with moldboard plow tillage (PT) and minimal tillage (MT) were measured in a 4‐yr field experiment on a Mattapex silt loam soil (finesilty, mixed, mesic, Aquic Hapludult) near Salisbury, MD (Atlantic Coastal Plain region). Labeled ammonium sulfate or ammonium nitrate (15N depleted) was applied annually to the entire area (74 m2) of each plot at five N rates ranging from 0 to 180 or 270 kg N ha−1. Corn dry matter yield, N content, and isotope composition were determined in the entire plant at the 11 to 12 leaf stage and at silage harvest, as well as in the corn grain at maturity. Below 135 kg N ha−1, dry matter yields, total N uptake, and fertilizer N (FN) uptake were greater with PT than with MT, but with 180 kg N ha1−1there was either no difference between the tillage systems or MT was greater than PT. Fertilizer N additions had no consistent or practically significant effect on soil N (SN) uptake. At 135 kg N ha−1, average crop FN recoveries were 62% for PT and 53% for MT, but this difference decreased with increasing N rate until both tillage systems averaged about 53% recovery at 180 kg N ha−1. Average SN uptake was greater with PT culture than with MT culture, averaging 76 kg N ha−1and 59 kg N ha−1, respectively. The crop N requirement of corn was about 17 kg N ha−1greater for MT corn than PT corn due to a 10% greater yield of total dry matter with MT. Corn grown with MT required about 68 kg more FN ha−1than PT, due to a lower uptake of SN and a greater crop N requirement. A lower uptake of N on MT plots during the second half of the growing season suggests (i) a greater net mineralization of N on PT plots and/or (ii) a greater loss of N via leaching and/or denitrification on MT plots. A nitrogen concentration of about 11 to 12 mg N g−1in the silage total dry matter, or about 15 mg N g−1in the grain, can be used as an approximate value for N sufficiency. However, these values should be considered broad guidelines since significant deviations were observed in individual years.

Variability in Optimum Nitrogen Rates for Maize

“…All primary sources of data, years, range in observed yields, and the predicted optimum N rate for all locations are reported in Table 1. Substantive published research has shown dramatic changes in optimum N rates varying from year to year at the same location (Al- Kaisi and Yin, 2003;Bundy et al, 2011;Eck, 1984;Fenster et al, 1978;Gehl et al, 2005;Ismail et al, 1994;Jokela and Randall, 1989;Mallarino and Ortiz-Torres, 2006;Meisinger et al, 1985;Olson et al, 1986;Peterson and Varvel, 1989;Randall et al, 2003;Rice et al, 1986;Shapiro and Wortmann, 2006;Stecker et al, 1993;Varvel et al, 2007;Vetsch and Randall, 2004;Woodruff et al, 1984). Nonetheless, given the importance of N for both crop production and the environment, no single document addresses the comprehensive nature of the problem or provides realistic and accurate estimates of the present variability in N rate recommendations.…”

Relationship of soil organic matter dynamics to physical protection and tillage

“…In the process of SOM turnover, the microbial biomass is considered to contribute to the labile pool of nutrients and C. Therefore, increased labile N under NT soils may be related to the general observation of a higher microbial biomass. Experiments with 13 C labelling helped to assess differences in the size of soil active N pool under different tillage practices (Fredrickson et al, 1982;Kitur et al, 1984;Carter and Rennie, 1984;Meisinger et al, 1985;HaugenKozyra et al, 1993). They showed a greater immobilization and a lower ef®ciency of use by the crop of fertilized N under NT.…”

Chemical stabilization of soil organic nitrogen by phenolic lignin residues in anaerobic agroecosystems

“…Future research will explore the hypothesis that covalent binding of N into stable forms such as anilide slows the rate of N mineralization while also extending its duration into late season crop growth stages and the subsequent fallow period. As long as the field remains flooded, mineralization of covalently bound N may by ARTICLE IN PRESS Carefoot et al (1990) Wheat-barley/Alberta Clay et al (1990) Corn/Minnesota Kitur et al (1984) Corn/Kentucky Meisinger et al (1985) Corn/Maryland Rice et al (1986) Corn/Kentucky itself be too slow to meet peak crop N demand at the onset of crop reproductive growth in mid-season. Whether the accumulation of phenolic lignin residues and their binding with soil N leads to yield losses can depend on several factors.…”