1990 Annual Report for LS90-020
Effective Nitrogen for Low-input Forage and Grain Production in a Thermicudic Region
Summary
Effective and economical alternatives for meeting nitrogen (N) requirements in crop production are crucial for low-input agricultural systems on thermic Udult soils which comprise the 15.3 x 106 ha Southern Piedmont region. Organic N from animal manure and winter legumes are potential sources for the region; however, management, effectiveness, and economics of these sources are uncertain and merit study. It is proposed that the efficacy of N supplied by these organic sources for grain and forage production be described and compared with a conventional inorganic N source and a combination of organic and inorganic sources. This will be done over a 3-year period on small watershed and farm field scales enabling a sampling of daily rainfall distribution and its impact on N efficacy of the sources, as well as assessment of cumulative treatment effects and economic performance. Experiments will focus on N supply to small grain and forage crops, both animal- and machine-harvested. Effects of animals on water quality in low-input systems will be assessed in a gauged watershed. N inputs will be accounted for and their availability and synchronization with crop needs will be described.
A diverse team of participants will be involved, including farmers, technology and information transfer persons, commercial producers, and research scientists. All participants are committed to accomplishment of all project objectives, from planning experiments to technology transfer.
On two watersheds, P1 and P2, crimson clover was no-till planted in the fall of 1990 and 1991. A pattern of points was established on each watershed for sampling crops and soils. On each watershed forage millet was no-till planted into the clover in May and harvested as hay in 1991. A preliminary nitrogen budget for P1 in the May through September 1991 period shows that about 100 kg/ha N was mineralized from soil and legumes sources and that the same amount was harvested in millet. However, analysis of soil samples taken in 1990, 1991 and 1992 from P1 to a depth of 2.9 m indicated that concentrations of nitrate near 20 mg ha -1 were commonly found between depths of 1.4 and 1.7 m. A similar zone of elevated nitrate concentration was not found in P2. It is, therefore, concluded that the current crop culture is efficiently utilizing the available mineralized N in hay production.
Objectives
(1) Describe the efficacy of organic and inorganic sources of N in forage production with animal and machine harvesting in intensive studies at experimental watershed and farm field scales.
(2) Evaluate the potential for surface and groundwater contamination by the systems studied in Objective 1.
(3) Describe the economic characteristics of the various N management systems.
(4) Through farm scale research and communication with farmers and technology transfer agencies, conduct technology transfer programs for efficient N management systems.