Winter Pea Is a Promising Crop for Washington's Winter Wheat-Fallow Region.

A long-term winter pea (WP) (Pisum sativum L.) cropping systems experiment was initiated near Ritzville, WA (292 mm average annual precipitation) in the September 2010. The objective of the experiment is to determine the suitability of winter pea in the traditional winter wheat–summer fallow (WW-SF) region of eastern-central Washington and north-central Oregon. Two 3-year crop rotations were tested: (i) WP-spring wheat (SW)-SF versus (ii) WW-SW-SF. Experimental design was a randomized complete block with four replicates of each treatment. All treatment combinations are present each year, making a total of 24 plots. All plots were 100 feet long. The WP variety “Windham” was selected for inclusion in the experiment. Windham is a feed pea with upright growth habit and good cold tolerance that can be direct combined with a regular header (i.e., swathing and/or a pick-up header not required). Winter pea has a large seed that is capable of emerging through five inches or more soil cover. Winter pea used significantly less soil water that WW. However, over the winter months, a higher percentage of precipitation was generally stored in the soil following WW compared to WP. The reason for this was because: (i) very little WP residue remains on the soil surface after harvest compared to WW, and (ii) the drier the soil, the more precipitation will be stored in the soil over winter. The end result, however, was that when SW was planted in late March, soil water following WP was significantly greater than that after WW. In the first five years of the study, WP yields averaged 2094 lbs/acre versus 72 bushels/acre for WW, with similar gross economic returns. Winter pea was killed by cold temperatures during the winter of 2013-2014. We, therefore, replanted the plots to the edible “Banner” spring pea. The yield of spring pea in 2014 was 778 lbs/acre. The yield of the subsequent SW crop was significantly greater after WP compared with after WW. Based partially on the successful early results of this study, several farmers in the low-precipitation region have started planting WP their farm ground.