Submitted to: Soil and Tillage Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/30/2010
Publication Date: 1/26/2011
Citation: Moroke, T.S., Schwartz, R.C., Brown, K.W., Juo, A.S. 2011. Water use efficiency of dryland cowpea, sorghum and sunflower under reduced tillage. Soil and Tillage Research. 112:(1)76-84. Interpretive Summary: Combining drought-adapted, early maturing crops with reduced tillage can help to stabilize and increase crop yields in the southern High Plains. A study was conducted to evaluate sorghum, sunflower, and cowpea grain yield response under dryland conditions in relation to depletion of water in the soil. Soil moisture at planting was greatest under no tillage compared with stubble-mulch tillage. Sorghum and sunflower used the most soil water throughout the growing season. However, sorghum used water more efficiently to produce grain compared with the other crops. Because cowpea matured early without using all of the available soil water, it could be used in a no tillage rotation with deeper rooted crops such as wheat and sorghum to intensify dryland crop production.
Technical Abstract: Drought-adapted, early maturing crops combined with reduced tillage systems have the potential to stabilize and increase dryland crop yields in the Southern High Plains. The objective of this study was to evaluate dryland grain yield response and soil water use for cowpea [Vigna Unguiculata (L.) Walp], sorghum [Sorghum bicolor (L.) Moench], and sunflower (Annus helianthus) under no tillage (NT) and stubble mulch tillage systems (SMT). The experimental design was a split plot, with tillage as the main plot and crop type as the subplot. Soil water contents were measured weekly throughout two growing seasons from 0.10 to 2.30 m depth, at 0.20-m intervals using a neutron moisture meter. Water use was based on the soil water balance calculated as the change in soil water storage plus precipitation measured at the research site assuming negligible runoff and percolation. Soil water content at planting was significantly greater under NT compared with SMT (P < 0.05). At harvest, soil water content was greater under cowpea compared with sorghum and sunflower in both tillage systems (P < 0.05). Soil water deficit index varied throughout the year and depended on rainfall distribution, crop type, and tillage systems. In 2000 and 2001, water use of sorghum and sunflower averaged 105 and 38 mm greater than that of cowpea across tillage treatments, respectively. Average grain water use efficiency (WUE) was greatest for sorghum (1.04 kg m**-3), followed by cowpea (0.55 kg m**-3) and sunflower (0.32 kg m**-3). Compared with SMT, the yield of sorghum and sunflower was greatest under NT. Based on soil water extraction and water use efficiency, cowpea and sorghum were the most suitable for a dryland cropping system in the Southern High Plains.