Organic and Inorganic Blended Materials for Use as Pop-Up Fertilizer for Cotton Seedlings

Abstract

Various factors such as soil moisture at planting, application rate, and composition of the fertilizer materials have contributed to the erratic results from use of starter and “pop-up” fertilizers. Earlier research with ammonium polyphosphate (11–37–0) has shown some beneficial effects on growth and lint yield of cotton (Gossypium hirsutum L.) when the starter was placed in the seed furrow or surface banded at time of planting. The purpose of this research was to determine the effect of starter fertilizer composition and application rates on cotton seedling emergence and early shoot/root growth at low and medium soil moisture regimes at planting. Treatments consisted of a control (0–0–0), 7–21–0, 5–15–0, and 3–9–0 liquid blends applied directly in the seed row at 3, 6, and 9 acre−1 to an Orelia sandy clay loam. The three blends contained 2.4%, 1.4%, and 1.0% by weight organic extract, respectively, and used ammonium orthophosphate as sole source of P. Standard-grade ammonium polyphosphate (11–37–0) was used for comparison at rates of 3 and 6 gal acre−1. The randomized complete block (RCB) experiment was conducted in the greenhouse for 35 days after planting (DAP). All pop-up fertilizers had a definite effect on cotton seedling emergence and early growth. Ammonium polyphosphate caused a marked delay in emergence even at 3 gal acre−1 during the first five days. Pop-up mix 3–9–0, at 6 and 9 gal acre−1, showed significantly less damage than other blends as well as the 11–37–0. At 11 DAP and adequate soil moisture, no difference among blends was observed but blended pop-up fertilizers had significantly greater (P < 0.05) emergence than 11–37–0, which produced only 30% emergence at 6 gal acre−1. Chlorophyll readings were only slightly greater for pop-up blends containing organic acids. Seedlings grown under less soil moisture showed a gradual decrease in plant height as pop-up rates increased whereas no effect was measured at adequate soil moisture. Fertilizer blends failed to increase final dry-matter yields of seedlings at 35 DAP when compared to the control whereas 11–37–0 decreased growth at certain rates. Where adverse effects from pop-up fertilizer treatments occurred, they were magnified by less soil moisture. Further research under field conditions is needed.