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Biological nitrogen fixation (BNF) is a key ecosystem service rendered by legumes, but quantitative information is lacking regarding BNF in the Texas Rolling Plains (TRP), an easterly portion of U.S. Southern Great Plains where cool-season legumes can typically be grown as cash or cover crops in dryland conditions. Using three diverse cropping systems studies (Site 1, long-term cotton [Gossypium hirsutum L.]cover crop systems; Site 2, short-term cotton-cover crop systems; and Site 3, transitional organic wheat [Triticum aestivum L.] system), our research objective was to quantify and compare BNF and associated parameters among four cool-season legumes (Austrian winter pea [Pisum sativum subsp. Arvense], hairy vetch [Vicia villosa], crimson clover [Trifolium incarnatum], and lentil [Lens culinaris]) in different settings. At Sites 1 and 2, winter pea had growth of 2.73 to 3.44 Mg ha −1 , the greatest percent N derived from the atmosphere (%Ndfa; 57.2-72.6%) and, depending on site, the greatest level of BNF (67-74 kg N ha −1 ). Results from the organic system (Site 3) demonstrated winter pea was also productive in growth and BNF when intercropped with wheat in N-poor soil, with exceptionally high %Ndfa (92.7%). Hairy vetch and lentil differed in growth and %Ndfa, but had comparable BNF (46-51 kg N ha −1 ) at Sites 1 and 2. Growth of crimson clover was poor. This data provides insights on how cool-season legumes differ in BNF in the TRP in a year when legume growth was average for the region. The TRP has a volatile climate, however, indicating further study is needed to fully understand the BNF benefit cool-season legumes can provide in the region. INTRODUCTIONCool-season legumes, grown as cash and cover crops, are a valuable component of cropping systems. Legumes can contribute to long-term accumulation of soil organic matter, Abbreviations: BNF, biological nitrogen fixation; %Ndfa, percent nitrogen derived from the atmosphere; TRP, Texas Rolling Plains.

The Southern Great Plains (SGP) region of the United States is widely known for its dryland dual-purpose winter wheat (Triticum aestivum L.) cropping systemsintegrated systems that provide both livestock grazing and grain production. Few of these systems are organic, however, and no relevant research had been conducted on this topic. A large-scale (41 ha) systems research study was conducted for 3 yr (2018-2021) to compare a transitional organic dual-purpose wheat system with a conventional one, with system management components customized to the ecological region. Organic wheat yield was 20% lower than conventional in the first season of organic transition, but there was no yield difference by the third year.The yield improvement in the organic system may be attributed to N fixation by a legume-based cash crop the previous winter season, exogenous nutrients from application of composted manure, and appropriate wheat cultivar selection. Because of limited moisture, relying on annual establishment of summer cover crops to fix N and deliver other ecosystem services in the organic system was not feasible in most years. Grain protein concentration (GPC) of the transitional organic wheat ranged from 91 to 103 g kg −1 , below the 120 g kg −1 threshold for a food market organic price premium. More intensive N management, including in-season application of a more available form of N that is organic approved, could be an effective strategy to increase GPC. This proof-of-concept study shows that organic dual-purpose wheat systems can be a viable enterprise in the SGP, though additional research is needed to address challenges identified herein. INTRODUCTIONAmong all grain crops, more acreage of wheat (Triticum aestivum L.) has been produced organically in the United States since 1995 than all other countries (McBride et al.

Guar [Cyamopsis tetragonoloba (L.) Taub.], also known as clusterbean, is a crop plant grown in semi-arid regions worldwide for the galactomannan gum of its seed, and as a forage, vegetable, and green manure. Despite the importance of guar and its products, uniform growth stage descriptions have not been established for the crop. Such descriptions allow for improved documentation and communication of the growth and phenological development of crops by researchers, producers, and others. Following models of other warm-season, indeterminant-growth legumes, such a system was developed for guar based on visually observable and sequential vegetative (V) and reproductive (R) plant events. The system was evaluated in two locations in dryland and irrigated conditions, using three morphologically contrasting guar varieties. The V stages begin with emergence (VE) and then are determined by counting the nodes on the main stem of the plant, with the cotyledonary node as zero [V0 to V(N)]. The R stages include R1 (First Flower), R2 (First Pod), R3 (First Seed or Full Pod), R4 (Full Seed), R5 (First Maturity), R6 (50% Maturity), and R7 (Harvest Maturity). The V and R stages may be reported alone or concurrently and applied at plant or crop scales. The stage descriptions apply to all growth morphologies of guar (i.e., branched and non-branched) and accommodate the indeterminant growth habit of the plant. Season-long data is reported from field studies on crop V and R stage progression, as well as data on crop growth, including biomass component partitioning, productivity, and canopy development.

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