Foliar Potassium Fertilizer Additives Affect Soybean Response and Weed Control with Glyphosate

Figure 4

Soybean grain yield response to K-fertilizer additives (%N-%P₂O₅-%K₂O-%S) of 3-18-18-0 (𝑦=63.659𝑥²−66.085𝑥+3660, 𝑅²=−0.07), 0-0-25-17 (𝑦=12.81𝑥²−59.903𝑥+3660, 𝑅²=0.79), 5-0-20-13 (𝑦=17.383𝑥²−12.125𝑥+3660, 𝑅²=−0.34), or 0-0-62-0 (𝑦=16.945𝑥²+65.878𝑥+3660, 𝑅²=0.74) applied alone to weed-free plots (a) and with glyphosate to weedy plots (b) for 3-18-18-0 (𝑦=0.628𝑥²+85.563𝑥+3357, 𝑅²=0.99), 0-0-25-17 (𝑦=−1.6925𝑥²+30.832𝑥+3357, 𝑅²=0.99), 5-0-20-13 (𝑦=−19.902𝑥²−20.694𝑥+3357, 𝑅²=0.40), and 0-0-62-0 (𝑦=−35.635𝑥²+45.506𝑥+3357, 𝑅²=−0.24) at Malden in 2004 and 2005. Data were combined over years, and comparisons between figures are valid. The nontreated, weed-free, and glyphosate plus nonionic surfactant plus diammonium sulfate grain yields were 3230, 3660, and 3570 kg ha⁻¹, respectively. There were no significant differences among treatments (𝑃=0.81) at this location.

(a)

(b)