Cotton and grain sorghum intercropping in West Texas
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Cotton production in west Texas has been the driver of economic growth in the region for the better part of a century. However, increasing costs of production and decreasing water availability have many producers looking for ways to cut costs and conserve water. One possible answer might lie in intercropping cotton with grain sorghum. Grain sorghum and cotton may be well-paired for intercropping, as both crops are drought-tolerant and have sufficient physiological differences to maximize yields in a shared water situation by properly timing irrigations to water critical periods of each crop. The primary physiological differences of note that make these good rotation partners in west Texas are; that grain sorghum can be planted at a lower soil temperature than cotton, they are different types of plants that can use selective herbicides to diversify crop protection chemistries, and both crops have short and long season varieties available to spread out the water critical periods. The primary goal of this study was to identify an optimal cropping system and irrigation regime that could maximize agronomic and economic benefits of shared supplemental irrigation. There were four supplemental irrigation regimes, two planting dates, two tillage treatments, and two varieties each of cotton and grain sorghum tested in 2016, and there was an additional irrigation treatment and an additional planting date tested in 2017. Final yield results and pricing data procured from local sources were used to determine gross revenue each year. From the gross revenue, key differences in production costs were deducted to determine revenue above seed, crop protection and irrigation costs for each crop. The observations showed that agronomic yield of both crops is maximized for an early planting (May 3rd) of grain sorghum, irrigated to replace 80% of weekly ET until July 15th, and a middle-to-late May planting of cotton, irrigated at 80% ET weekly after July 15th. Both of these crops have water critical periods at flowering which will occur between 50 and 60 days after planting. By spreading out the planting dates a producer can manage his water to be able to irrigate both of these crops around these periods. However, the cropping system for which economic value is maximized is cotton monoculture irrigated at 80% ET weekly throughout the entire growing season and dryland cotton on remaining acres. The benefits of intercropping cotton and grain sorghum will not be demonstrated in revenue, but in less-tangible benefits like diversified weed control options and chemistries, benefits to soil by increasing porosity, limiting soil exhaustion from cotton monoculture and increasing residue, which promotes reduced-till opportunities to limit erosion and reduce input costs. Over time, these ancillary benefits could turn into economic benefit.