Austrian Winter and Spring Peas as Green Manure Crops in Northern Idaho1

Abstract

AbstractThe increasing cost of N fertilizers has caused a renewed interest in the utilization of Austrian winter peas [Pisum sativum ssp. arvense (L.) Poir] as a green manure crop. From 1977 to 1980 field experiments on a palouse silt loam (fine, montmorillonitic, mesic Xeric Argialboll) were conducted in northern Idaho to determine the planting date, harvest date, and cultivar of Austrian winter peas that produced the maximum yield of organic matter (OM) and N in the vines. Organic matter yield was determined by harvesting and weighing the vines from four‐row plots (1.3 m2). A 1‐kg sample from each plot was dried and wet weights were adjusted to an oven dry basis. Vine N was determined using either micro‐Kjeldahl or a Technicon Autoanalyzer II System.Austrian winter peas seeded in early September produced the highest yields of OM and vine N. Delaying seeding until early October reduced OM production and vine N by over 50% at both locations. Vine N was increased only 28 kg/ha by delaying harvest from early bloom to late pod filling but OM yield was increased by 4.9 metric tons/ha.‘Melrose’ produced the most OM (13.9 metric tons/ha) and vine N (321 kg/ha) of the five winter pea lines evaluated. All of the lines accumulated in excess of 250 kg of vine N/ha averaged over both test years.The four long‐vined Austrian winter pea lines yielded an average of 13.0 metric tons of OM/ha when fall planted but only 6.9 metric tons/ha when planted in the spring. Six spring pea cultivars (P. sativum L.) averaged 12.1 metric tons/ha but late maturity would have prevented plow‐down under dryland conditions.In northern Idaho, Austrian winter peas could produce in excess of 10 metric tons/ha of OM which would contain a minimum of 175 kg/ha of vine N. The inclusion of Austrian winter peas as a green manure crop in crop rotations could have a significant impact on the total N budget of the soils in this region.