Doses e tempo de solubilização no solo do silicato de cálcio e de magnésio na população de Sitobion avenae (Fabricius) (Hemiptera: Aphididae) e na produtividade do trigo

Abstract

Wheat, Triticum aestivum (L), is a silicon (Si) accumulating plant and its yield in the Brazilian savannah is reduced due to the intensity of damages caused by the English Grain Aphid, Sitobion avenae (Fabricius). Thus, this study evaluated the effect of Si doses and reaction time of calcium and magnesium silicate in the soil on wheat resistance induction against the aphid S. avenae and on the productivity of wheat and corn. Five doses of soluble Si were tested (0, 400, 600, 800 and 1000 kg ha-1), using calcium and magnesium silicate as the Si source. Crops of wheat (winter 2019), maize (summer 2020) and wheat (winter 2020) were grown in succession in the same area, and were sown 50, 195 and 375 days, respectively, after Si application to the soil. Eleven weekly evaluations were done per wheat crop season, counting the number of aphids in 10 tillers per plot. The application of silicate linearly increased Si availability in the soil, from 6.2 mg kg-1 (prior to silicating) to 12.61 mg kg-1 (at the Si dose 1,000 kg ha-1, after the second wheat harvest). The percentage of Si in wheat plants at Z94 stage increased linearly with increasing soil Si, from 1.21% in the control to over 2% at the higher doses. In contrast, leaf Si content in maize adjusted to a quadratic model, increasing from 0.64% in the control to 0.79% in the maximum inflexion point (716 kg Si ha-1). Amending the soil with silicate resulted in a linear reduction in the number of S. avenae in wheat plant in both seasons, decreasing aphid population by 29% at the dose of 1,000 kg ha-1. However, yield of wheat and corn were unchanged. Soil application of calcium and magnesium silicate over 400 kg ha-1 induced resistance in wheat plants sown at both 50 and 375 days after soil amendment, reducing the population of the aphid S. avenae in field conditions. Silicon is a viable alternative to improve wheat integrated pest management.