Title:

Grass Seed Cropping for Sustainable Agriculture

Investigators:

Stephen M. Griffith, USDA-ARS
Jeffrey Steiner, USDA-ARS
Glen M. Murray, University of Idaho
Allan Mitchell, Oregon State University

Progress:

Objective 1.

Agronomic Practices for Reduced Smoke and Nitrate Pollution from Kentucky bluegrass Seed Production

Smoke from burning of post-harvest residue from Kentucky bluegrass seed fields and potential ground water contamination from nitrogen application are environmental concerns. The purpose of this study was to test combined economic effectiveness of crew-cutting, one of the most current mechanical after-harvest residue removal techniques, enhanced ammonium nutrition, and bluegrass variety growth response as a production package needed to eliminate burning and to improve nitrogen use efficiency of Kentucky bluegrass. Field trials were established at three locations in Idaho, (Moscow, Coeur d' Alene, Worley), and at two locations in Oregon, (Madras and La Grande). Seed yields of most bluegrass varieties were not adversely affected by one year of crewcutting as a substitute for burning. Data from adjacent commercial fields showed similar results. However, yields declined with crewcutting compared to burning in the second year in commercial fields. (Further information concerning cultivar by crewcutting response can be found in the report by Dr. Glen Murray). Five bluegrass cultivars established at the Idaho and Oregon locations responded similarly to nitrate and ammonium nitrogen. Our results indicate that mechanical residue removal could be an alternative to burning in the second year of seed production if economic methods of removal are found. Ammonium nutrition can be used without adversely affecting seed yield in Idaho and Oregon, thus reducing potential nitrogen losses to underground water supplies. This project will conclude in 1996.

Objective 2.

Nonthermal Grass Seed Production System Research

Alternative cropping systems are being investigated for three conventional perennial grass seed species grown in three divergent environments. Most grass-seed cropping systems in western Oregon lack diversity and as such do not utilize the potential beneficial effects of crop rotations. Legume seed crops in rotation with grass benefit grass seed production systems by: 1) breaking the life cycles of many insect and weed pests that are persistent and difficult to control under grass monculture, 2) providing an important source of biologically fixed nitrogen, improving soil tilth and general soil health, and assisting with soil stabilization and thus reduce erosion, 3) helping to incorporate crop residues that also stabilizes the soil, and 4) improving fertilizer recovery from grass straw residues. In 1994 and 1995 maximum straw residue compared to low residue management did not significantly reduce seed yield or above ground biomass in tall fescue. Tall fescue seed yield following clover rotation was 1,063 lb ac-1. This yield was achieved with only 38 lb N ac-1 fertilizer applied. This yield compared to non-rotated tall fescue seed yield of 870 lb ac-1 and 150 lb ac-1 of N applied. To the grower this rotation response equates to a savings of $43.00 ac-1 in fertilizer costs. Tall fescue growth (above ground biomass) was increased and harvest index reduced following a clover rotation compared to the non-rotated crop. This may be attributed to a nitrogen response.

Objective 3.

Water and Nitrogen Use of Kentucky Bluegrass Cultivars under Different Residue Management System

Water allocation for agriculture use and maintenance of high water quality are matters of increasing concern in the arid Northwest. Since high quality bluegrass seed is produced in arid regions on both irrigated and rain-fed land, it is important to document the crop water and nitrogen use of bluegrass to produce optimal seed yield. In non-irrigated regions it is important to investigate how seed yield responds to rainfall under the non-thermal residue management. This project was recently initiated to investigate water and nitrogen use of aggressive and non-aggressive Kentucky bluegrass cultivars under three residue management treatments. Preliminary data showed that there was no difference in water use between aggressive and non-aggressive bluegrass cultivars. Water use averaged 19.5 inches (494 mm) for 1994 (Madras, OR), which is higher than most estimates.

A long-term project was initiated the fall of 1995 to further this investigation. Additional information of this project is provided in a report by Dr. Alan Mitchell (see USDA-CSREES annual reports for the GSCSSA).