Efeito de doses de molibdênio aplicadas na fase de enchimento De grãos do feijão-caupi no conteúdo de molibdênio da semente e na sua qualidade fisiológica

Abstract

Cowpea has socioeconomic importance, mainly for the North and Northeast of Brazil, where it constitutes one of the main components of the diet of needy families. Molybdenum (Mo) is the micronutrient required in small quantities for plant growth, but it can reduce the quality of harvested seeds. Our objective was to test the hypothesis that foliar application of Mo, with a relatively high dose in the grain filling phase, may harm the physiological quality of the seeds, but increases the seed Mo content (CMoS) of cowpea grown in the region. subtropical region of Brazil. Three field trials were conducted with cowpea in Maranhão: one in Guimarães (2021) and two in São Luís (2021 and 2022). The trials consisted of six treatments with Mo (g ha-1) (Na2MoO4.2H2O) via foliar: T1 = No Mo; T2 = 50 (V6); T3 = 50 (V6) + 400 (R4); T4 = 50 (V6) + 200 (R1) + 200 (R4); T5 = 50 (V6) + 300 (R1) + 100 (R4); T6 = 50 (V6) + 400 (R1). The design was in randomized blocks, with four replications. Five orthogonal contrasts were tested: C1= T1 vs T2-6; C2 = T2 vs T3-6; C3 = T3-4 vs T5-6; C4 = T3 vs T4; C5= T5 vs T6. Grain yield and CMoS data were obtained from three trials and physiological quality data from one trial. The treatments influenced grain yield (P=0.002), CMoS (P<0.001), germination (P=0.021), electrical conductivity (P=0.004) and dry seedling mass (P<0.001). The treatments did not influence accelerated aging (P=0.169). The CMoS of plants that received Mo was 8.5 times greater than the CMoS of plants that did not receive Mo (P<0.001). The dose of 400 g ha- 1 of Mo (4 treatments) increased CMoS 3.2 times in relation to the dose of 50 g ha-1 (V6) (P<0.001). The doses of 200 and 400 g ha-1 applied in R4 increased germination by 4.0 percentage points in relation to the absence of Mo and 100 g ha-1 of Mo (contrast T3-4 vs T5- 6; P=0.020). Our results indicate that the application of most of the Mo in the R4 phase of cowpea (400 of the 450 g ha-1 of Mo) does not cause an increase in CMoS in relation to splits in the R1 and R4 phases. And they indicate that there is no advantage in making three installments of the total dose of Mo compared to two installments