Fertilization Strategies of Cotton in North Carolina

Abstract

Upland cotton (Gossypium hirsutum L.) can be a difficult crop to manage due to the intermediate growth habits, tropical origins, and perennial nature. Because cotton is produced as an annual in North Carolina, it is highly important to promote maximum early season growth, stimulate early flowering, and at the same time prevent excessive vegetative growth, all which are important to harvest quality cotton. The use of several management practices may be applied to promote earliness, and achieve high yields. While environmental conditions can generally not be controlled, they can be altered thorough tillage methods, plant growth regulator use, and desirable fertilization programs, to manipulate cotton vegetative and reproductive growth to promote high yields. Three studies were conducted to observe fertilization strategies for cotton production in North Carolina. One study was conducted in North Carolina and Virginia during 2005 and 2006 to determine effects of increased N fertilization rates and increased plant growth regulator rates on a modern cultivar. The second study were conducted in North Carolina in 2006 and 2007 to observe the effects of effects of starter fertilizer in conventional, strip†till (ST) and no†till (NT) systems on growth, quality and yield of cotton. The third study was conducted in North Carolina in 2006 and 2007 to determine optimal N placement methods in strip†till (ST) and no†till (NT) systems based on growth, fiber quality, and yield of cotton. Data from the first study showed that N rate affected yield in Virginia in both years and in North Carolina during 2006. However, in 2005 N did not affect yield. In North Carolina 2006 the response to N was quadratic, while in the Virginia locations the response to N was linear, however, further increase in N above 112 kg N ha†1 was not significant. Overall the use of a plant growth regulator did not alter the optimum N rate. For the second starter fertilizer did not have an effect on yield in either year. Starter fertilizers did have an effect on early season vigor and plant heights in 2006 with the 11†37†0 fertilizers having greater vigor and heights. In 2006 and 2007 11†37†0 fertilizers had the highest dry weights. Data from both years suggest that tillage has an influence on early season growth such as vigor, stand counts, and early season heights. Data from 2007 indicates that more bolls may be produced in NT systems, however, the number of bolls did not correspond to an increase in lint yield. Little agronomic advantage was found in starter fertilizer, with no positive or negative effect on yield when compared to an untreated control. There is no conclusive evidence from the data that starter fertilizer responses are more likely for any tillage system. For the third study data from 2006 found that under reduced tillage systems broadcasting N was sufficient, while injecting N did not improve final yield. Data from 2007 indicates that the placement of fertilizer N at first square had no significant effect on final yield. Due to the lack of sufficient tillage by N method interactions, it is likely that all N application methods would perform similarly in both tillage systems. Based on these data an optimal N placement strategy could not be determined based on the data, due to the inconclusive results regarding application method effects on growth and yield.