Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2003
Publication Date: 9/1/2003
Citation: PETTIGREW, W.T. RELATIONSHIPS BETWEEN INSUFFICIENT POTASSIUM AND CROP MATURITY IN COTTON. AGRONOMY JOURNAL. 2003. v. 95. p. 1323-1329. Interpretive Summary: Despite considerable research conducted on cotton potassium fertility over the past fifteen years, questions and misconceptions still exist concerning the effects that adequate and deficient potassium levels have on cotton growth and development, yield, and fiber quality. It is already known that potassium deficiency depresses cotton yield by causing an early termination of reproductive growth. In addition, popular opinion and anecdotal evidence suggests that high yielding, fast fruiting, early maturing varieties may be more susceptible to potassium deficiency than later maturing varieties. This study investigated whether the early crop maturity caused by potassium deficiency was partially caused by earlier initiation of flowering, in addition to the premature termination of reproductive growth. It also investigated whether early maturity, in and of itself, caused varieties to be more susceptible to potassium deficiency. Results showed that the early season flowering rate was briefly increased 11 % in plant grown under K deficient conditions. Therefore, the potassium deficiency acceleration of cotton crop maturity is due to both a premature end to reproductive growth and to a brief enhancement of early season flowering. Results also show that an early maturity does not inherently predispose a variety to be more susceptible to potassium deficiency. Another characteristic, possible reduced root systems, may cause some early maturing varieties to be more susceptible to potassium deficiency. This information will prove useful to cotton breeders in variety development decisions regarding maturity and to producers when deciding which variety to plant. Producers on the northern fringe of the cotton production belt, forced into late planting situations, or planting a normally late maturing variety should take into consideration the extension of the growth period produced by K fertilization that allows it to achieve its superior yields.
Technical Abstract: Potassium deficiency in cotton (Gossypium hirsutum L.) depresses yield by shortening the growing season and is reportedly more harmful to early maturing cotton genotypes. The objectives were to determine if the accelerated crop maturity caused by K deficiency was partially caused by earlier flowering and to conduct a more direct test of whether early maturity in a genotype causes it to be more susceptible to insufficient K levels. Field studies were conducted from 1995-1997 utilizing two okra-normal leaf-type near isoline pairs and two levels of K fertilization (0 kg K ha-1 and 112 kg K ha-1 ). Okra leaf-type genotypes are earlier in maturity than their normal leaf-type counterparts. Weekly white bloom counts, dry matter partitioning, canopy light interception, lint yield, yield components, and fiber quality data were collected. Genotypes responded similarly to varying K fertilization levels for all of the data gathered. The early season flowering rate was briefly increased 11 % in the plants grown under insufficient K conditions. Late season leaf area index (LAI) was 23 % lower in the 0 kg K ha-1 treatment plants compared to the 112 kg K ha-1 treatment in two of the three years. The increased leaf area of the 112 kg K ha-1 treatment allowed it to intercept 6 % more of the late season sunlight compared to the 0 kg K ha-1 treatment. Two out of three years K fertilization increased lint yield 9 %, but insufficient K had only minor effects on fiber quality during this study. Early maturing cotton genotypes are not inherently more susceptible to insufficient K levels because of their early maturity. The K deficiency acceleration of crop maturity is due to both a premature termination of reproductive growth and a brief enhancement of the early season flowering rate.