CRIS Project: Cotton Physiology

2008 Outcomes/Impacts

The project found that changes in normalized difference vegetation index (NDVI) of mid- to late-season cotton are predictive of crop maturity differences governed by nitrogen or potassium nutrition.  Results suggest that ground-based NDVI sensing provides data that indicates the progress of crop maturity. Economic impacts of this finding derive from reducing the current cost of cotton crop monitoring, and scheduling the optimum defoliation timing for lint yield and fiber quality.

The project reported to producers that planting cotton in a 2x1 skip-row pattern can reduce planting costs with minimal loss of lint yield or earliness in relatively narrow row widths. Reducing planting costs by one-third are particularly helpful to producers interested in planting cotton in 15- or 30-inch rows for spindle picking. Assuming a cost of $185 per hectare for seed and technology fees for solid planting, adoption of 2x1 skip rows on 20% of hectares planted to cotton in Tennessee would save $1.5 million in production costs annually.

2008 Research Report

This project continued research on the use of Normalized Difference Vegetative Index (NDVI) in cotton. We conducted three separate field experiments on NDVI in 2008, including effects of different cover crop and nitrogen fertilization regimes; effects of different rates and timing of irrigation water application; and effects of different plant growth regulators. Results so far suggest that producers may be able to monitor crop maturation more efficiently by NDVI sensing of than by traditional methods, but interpretation of NDVI data from cotton needs more research. 

The project published results from a study of alternative row spacings and planting patterns for cotton grown with and without supplemental irrigation. Narrower rows and solid plantings tended to close canopy earlier and more completely, to suppress weed growth, and to mature earlier than in wider rows and skip-row patterns. Skip-row cotton matured later than solid planting, but this effect diminished with narrower rows. With or without irrigation, lint yields were 13 to 15% lower in 102-cm skip-row cotton than in 102-cm solid planting, but yields did not differ between solid and skip-row in narrower rows.  Cotton producers interested in skip-row planting should consider rows spaced 76-cm or less to minimize weed problems and yield loss.

The project also completed a sponsored study in 2008 to evaluate the potential of 38-cm row cotton intended for spindle picking. Producer interest in this research stems from the high cost of planting seed and transgenic technologies, along with interest in a new 38-cm row spindle picker that is commercially available. We reported similar yields from 38-cm solid and skip-rows, and 76-cm solid rows, but lower yields in 76-cm skip-rows in our plots. Fiber quality was equivalently high in all row spacings. Cotton producers interested in 38-cm cotton should consider a skip-row pattern to reduce planting costs.

The project also continued a sponsored study on effects of mineral nutrition on lint yield and fiber quality of cotton in 2008.  Tennessee producers are concerned about symptoms of sulfur (S) and micronutrient deficiencies observed more frequently in recent years.  We conducted a field study of cotton response to S and zinc (Zn) fertilization on a low-testing soil, and a study of S deficiency in container-grown cotton. In field plots, foliar S concentrations increased in response to 20 or 30 lb/ac S applied at planting, but yield responses to S or Zn fertilization were not significant. With more severe S deficiency induced in container-grown cotton, boll size and seed weight were reduced significantly.  More research is needed before extension recommendations can be formulated.