N Behavior Under No‐Till vs. Conventional Corn Culture. I. First‐Year Results Using Unlabeled N Fertilizer¹

Abstract

This study comparing corn yields from different rates of applied N under no‐tillage and conventional culture was prompted by numerous field observations in Maryland that no‐till corn, with low to moderate rates of N, often showed more pronounced N deficiency symptoms than did conventionally tilled corn. Little is known regarding the relative N requirements of untilled corn grown in cover‐crop residues as compared to conventional tillage. The purpose of this study was therefore, to determine whether tillage method affected optimal crop requirements for fertilizer N. First‐year effects of tillage method and fertilizer N applications (0, 45, 90, 135, and 180 kg/ha) on corn (Zea mays L.) yields, N uptake by the crop, mineral N accumulation in the soil, and total and potentially mineralizable soil N are reported. With suboptimal N rates, N deficiency symptoms were more severe throughout the season on untilled than on cultivated plots. However, the optimal level of applied N for grain and dry matter yields did not differ with tillage method. After grain harvest, the amount and distribution of residual mineral N in the root zone for a given rate of applied N were similar in tilled and untilled plots at two locations (Poplar Hill and Plant Research Farm). At the third site (Wye Institute), however, residual mineral soil N was higher with conventional than with no tillage. These differences were attributed to variation among sites in amounts of precipitation between planting and harvest, as it affected relative water infiltration in tilled and untilled plots. Total residual mineral N in the root zone tended to increase with N application rate. Between harvest (1973) and planting (1974), however, most of the residual mineral fertilizer N was removed by the cover crop or lost. Total soil organic N to a depth of 30 cm was unaffected by N rate or tillage method during one cropping season. At one rate, however, potentially mineralizable N was higher in untilled than in tilled plots. Studies are continuing on two of the sites, with l5N‐lepleted fertilizer, to determine relative changes with time in soil N status as influenced by tillage method.

Dryland maize development and yield resulting from tillage and nitrogen fertilization practices

“…This is contrary to suggestions by Thomas et al (1973), Bandel et al (1975) and Moschler and Martens (1975), who indicated that increased N fertilizer application rates were necessary for no-till to achieve yields equivalent to conventional tillage (plow). However, Thomas and Frye (1984) indicated that N requirements for plants grown under conventional tillage and no-till were similar if yields were similar.…”

“…These data indicated that the water conservation potential of reduced-tillage practices was not sufficient to improve maize yield. Also, contrary to some earlier reports (Thomas et al, 1973;Bandel et al, 1975;Moschler and Martens, 1975), it does not appear that, in this climatic zone, maize produced without tillage requires more N fertilizer. "LAD (M) has units of modified growing degree days ( "C day).…”

The potential to mitigate global warming with no‐tillage management is only realized when practised in the long term

“…surprising because of a transient yet significant N deficiency which lowers crop yields in recently established NT systems (Bandel et al, 1975;Blevins et al, 1977;Rice et al, 1986;Vetsch & Randall, 2000). This observed N deficiency has been associated with increased N 2 O-emissions in NT systems (Burford et al, 1981;Rice & Smith, 1982;Linn & Doran, 1984).…”

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

“…At some locations, decreased availability of soil N was associated with a loss of crop yield. In other studies lacking labeled fertilizer, symptoms of N deficiency were more evident in no-tilled crops than with conventional tillage (Thomas et al, 1973;Bandel et al, 1975). To date the effects of notillage on the chemical nature of SOM have received little attention.…”