Plant Responses of Ultra Narrow Row Cotton to Nitrogen Fertilization

Abstract

ABSTRACT Recent developments in cotton (Gossypium hirsutum L.) production technology in the Mississippi River Delta region include drill planting cotton. Production systems that include drill planting cotton are referred to as ultra narrow row (UNR). Ultra narrow row cotton production is a low input system designed to maximize economic returns. Cotton grown under UNR systems is generally lower yielding and lower returning than conventionally spaced cotton, but the inputs and input costs are also generally reduced compared to conventionally spaced cotton production systems. Studies were conducted for five location-years in southeastern and northeastern Arkansas to determine the optimum N-fertilizer rate for UNR cotton. Plant maturity was estimated using nodes above white flower (NAWF) measurements. The NAWF indicated that greater nitrogen (N)-rates delayed maturity of the crop, although differences were not always significant. Lint yields were significantly different in only three of five location-years. Yield responses of UNR cotton tended to maximize with N-treatments between 56 and 84 kg N ha− 1 when significant differences were observed. Plant height, similar to lint yield, was significantly different due to N-treatments in three out of five location-years, and generally increased with increasing N-fertilization up to 112 kg N ha− 1. Boll load was significantly influenced by N-fertilization in only two of five location years. In these two instances, 84 kg N ha− 1 was sufficient to maximize boll load. Boll weight, a component of yield, was determined in the southern Arkansas location only. Significant differences in boll weight due to N-fertilization were found in only two of four years. Boll weight generally increased with increasing N-fertilization.