Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton

Abstract

Research investigating row spacing in high-yielding, high-input cotton (Gossypium hirsutum L.) production systems has found higher lint yields but no maturity benefits using high plant density, 25 cm spaced ultra-narrow rows (UNR). Seven experiments comparing 38 cm UNR and conventionally spaced rows (100 cm) were conducted over three years to determine if changes in plant density or management could optimize yield and maturity in a high-input UNR cotton production system. Two of these experiments compared 25, 38 and 100 cm spaced rows under different intra-row plant density (12 to 36 plants m−2). Three experiments managed 38 cm UNR and 100 cm spaced rows separately and one had extra early application of nitrogen and water. Across the seven experiments there were no differences in lint yield or crop maturity for 38 cm UNR compared to conventionally spaced rows. The only significant response to changes in inter- or intra-row density or agronomic management was an 18% increase in handpicked lint yield in the 12 plants m−2 38 cm UNR treatment compared to the same plant density in 100 cm spaced rows in one of the two experiments. This stability of yield response across row spacings indicates that there is an opportunity to reduce seed rates whilst maintaining yields in high-input UNR systems. UNR cotton did not require any difference in mepiquat chloride or nitrogen management compared with conventionally spaced cotton, nor did extra early inputs of nitrogen or water, and we concluded that is likely that the current recommendations for mepiquat chloride or nitrogen nutrition in conventionally spaced systems are appropriate for managing high-input UNR cotton crops.