Perennial wheat: The development of a sustainable cropping system for the U.S. Pacific Northwest

Abstract

Perennial wheat offers a new solution to the long-standing problems of soil erosion and degradation associated with conventional annual small-grain cropping systems in the Pacific Northwest region. Using classical breeding methods, new types of wheat have been developed that maintain the key characteristics of annual wheat, but continue to grow after harvest. Following dormancy in the winter, growth is initiated from the roots or crowns in the spring, allowing a crop to be harvested every fall. By retaining constant soil cover over multiple years, wind and water erosion would be dramatically reduced. In addition, the costs associated with annual seeding and tillage would be minimized, and unlike many reduced tillage systems, it is expected that standard seeding equipment would be suitable for stand establishment. Other potential benefits of perennial wheat include improved wildlife habitat, more efficient use of available water, provision of a potent carbon sink, and the possibility of integrating straw retrieval into a small grains cropping system. Past attempts in the first half of the last century failed to develop perennial wheat as a viable crop, primarily because of low yields, and the research was ultimately abandoned. Perennial wheat production may now be viewed as acceptable for highly erodible land or for obtaining carbon sequestration credits. This paper presents an overview of solutions to the obstacles encountered by previous researchers, introduces some of the newly developed perennial wheat lines, and discusses considerations for management practices.

Breeding Perennial Grain Crops

“…Other, less far-reaching recommendations for reducing soil erosion also involve perennial grains (Wagoner, 1990a;Scheinost et al, 2001). But all of our major grain crops are annuals, and no current perennial species produce sufficiently high yields.…”

“…Suneson et al (1963) reported that their 25 years of work with perennial wheat (Triticum aestivum hybridized with perennial grasses) in California had produced lines whose first-year yields fell "within the range of the lowest yielding commercial wheat varieties" of the time, with a rapid yield decline in subsequent years. Recently, eight intergeneric wheat lines selected for regrowth ability in Washington state, USA yielded between 1600 and 5800 kg/ha, compared with almost 9000 kg/ha for the popular annual wheat cultivar 'Madsen' (Scheinost et al, 2001).…”

“…Basal or rhizome-derived tillers on a grass plant are largely selfsufficient (Nyahoza et al, 1973;Jackson and Dewald, 1994), and their own inflorescences can supply much of the photosynthate for seed development (Blum, 1985). Perennials also may be able to maintain green tissue and continue to photosynthesize late in the growing season, after the photosynthetic tissue of annuals has senesced (Scheinost et al, 2001). For all of these reasons, there need not be a gram-for-gram tradeoff between grain and perennating structures.…”

“…elongatum (2n=14) are caespitose. Researchers at Washington State University have launched a new program to develop perennial wheat from Thinopyrum crosses, with promising preliminary results (Scheinost et al, 2001;Cai et al, 2001). As we shall see (III.A.3.…”

“…Most efforts to breed perennial grains have environmental protection as an explicit goal. This will lead breeders to select genotypes adapted to systems like organic farming (Wagoner, 1990b;Scheinost, 2001) or natural systems agriculture (Jackson and Jackson, 1999) that receive lower subsidies of nonrenewable energy and synthetic chemicals. Such systems usually incorporate inter-and intraspecific diversity.…”