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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/22/2013 Publication Date: 7/1/2013 Citation: Baumhardt, R.L., Schwartz, R.C., Howell, T.A., Evett, S.R., Colaizzi, P.D. 2013. Residue management effects on water use and yield of deficit irrigated cotton. Agronomy Journal. 105(4):1026-1034. Interpretive Summary: The declining Ogallala Aquifer of the U.S. Southern High Plains limits irrigation and dictates saving rain for later crops. We adapted a three year dryland rotation that produces wheat and cotton plus a fallow period by adding deficit irrigation. Our experiment also tested disk (DT), stubble-mulch (SM) or no (NT) tillage to save water on a Pullman clay loam at the USDA-ARS Conservation and Production Research Laboratory, Bushland, TX. We quantified tillage effects on water storage plus cotton water use and yield for full and deficit irrigation. Wheat straw cover with SM and NT increased water stored during fallow up to 2 inches over DT. Growing season water use diverged slowly between irrigation levels, but provided from more than 70% of the calculated water need. Cotton water use decreased as straw cover decreased in the order NT > SM > DT. Cotton yield did not vary between irrigation levels that met crop water demand. Yield increased with NT by 500 lbs/ac or about 50% over DT. We conclude that NT has less evaporation from the soil than DT. Cotton used the saved water to meet needs and increase lint yield. Technical Abstract: The declining saturated thickness in much of the Ogallala Aquifer beneath the Southern High Plains decreases irrigation well capacity and necessitates conservation of precipitation during rotation fallow periods for subsequent crop use. A three year dryland rotation that produces crops of wheat (Triticum aestivum L.) followed by cotton (Gossypium hirsutum L.) with intervening 10-month fallow periods was adapted for use with deficit irrigation at capacities of 2.5 mm d**1 and 5 mm d**1 on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) managed using disk (DT), stubble-mulch (SM), or no (NT) tillage at Bushland, TX (35 deg 11' N, 102 deg 6' W). Study objectives were to quantify tillage effects on soil water storage, and any continued effects on water use and yield by cotton grown under two irrigation capacities. Compared with DT, sufficient wheat residue cover was retained by SM and NT to increase the 4-yr study mean precipitation storage during fallow from 15 to 50 mm. Cumulative growing season water use diverged slowly between irrigation capacities, resulting in significant differences in measured water use that totaled from 70% to >100% of the estimated evapotranspiration (ET). Growing season water use decreased with decreasing residue cover in the order NT > SM > DT. Cotton yield did not vary between the irrigation capacities, which largely met the estimated crop ET for the years studied; but lint yields increased with NT by about 50% or 450 kg ha**1 over DT. Yields for DT cotton irrigated at 5 mm d**1 were typically less than for NT and SM cotton irrigated at 2.5 mm d**1. We conclude that NT residue management partitions ET for greater transpiration and, consequently, significantly greater lint yield than with disk tillage. |
