|Prior, Stephen - Steve|
Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/24/2002
Publication Date: 6/24/2002
Citation: Prior, S.A., Reeves, D.W., Delaney, D.P., and Terra, J.F. 2002. Effects of conventional tillage and no-tillage on cotton gas exchange in standard and ultra-narrow row systems. In Santen, E. van (ed). Making conservation tillage conventional: Building a future on 25 years of Research, Proc. of 25th Southern Conservation Tillage Conference for Sustainable Agriculture. pp. 334-338. Special Report No.1. Alabama Agric. Expt. Stn., Auburn University, AL. Interpretive Summary: Crop production in the U.S. is often limited by available soil water. Adoption of no-tillage farm practices can lead to more crop residue on the soil surface which can enhance soil water storage. Our goal was to evaluate cotton gas exchange during reproductive growth as affected by tillage practice (conventional tillage vs. no-tillage) and row spacing (standard 40 in vs. ultra-narrow row). The benefits of no-tillage are most probable in years experiencing sporadic precipitation during reproductive growth. Reflective of good soil water status, no-tillage cotton maintains higher rates of photosynthesis. In years with frequent rainfall during reproductive growth, the benefits of no-tillage are less frequent. Compared to standard row cotton, the benefits of no-tillage are less pronounced in ultra-narrow cotton which had lower rates of photosynthesis due to faster canopy closure and greater plant-to-plant competition for soil resources. Adoption of no-tillage practices can help minimize detrimental impacts of drought stress on cotton grown in coarse textured soils during critical reproductive periods such as boll filling.
Technical Abstract: The availability of soil water to crops is a major limitation to crop production. Use of conservation tillage systems enhances soil residue cover, water infiltration and reduces evaporative soil water loss. Our objective was to measure cotton (Gossypium hirsutum L.) leaf level photosynthesis, stomatal conductance, and transpiration during reproductive growth under different row spacing and tillage conditions on a Norfolk loamy sand (Typic Kandiudults; FAO classification Luxic Ferralsols) in east-central AL. Gas exchange measurements occurred in the summer of 1999, 2000, and 2001. The study used a split-plot design replicated four times with row spacing (standard 40 inch row and ultra-narrow row) as main plots and tillage systems (conventional and no-tillage) as subplots. In 1999, standard row cotton under conventional tillage maintained higher photosynthetic rates during early reproductive growth when soil water was not limiting; the opposite pattern occurred latter during drought cycles. During drought periods, photosynthetic rates were higher in no-tillage systems especially under standard row conditions. In 2000 and 2001, the benefits of no-tillage were sporadic due to frequent rainfall events occurring throughout reproductive growth. In 2000, ultra-narrow row cotton consistently had lower photosynthesis rates compared to standard row cotton; lesser degrees of this occurred in 1999 and 2001. In all years, stomatal conductance and transpiration measurements generally mirrored those of photosynthesis. These results suggest that during periods of infrequent rainfall, high rates of photosynthesis can be maintained in no-tillage systems that conserved soil water needed during critical reproductive stages such as boll filling.