Rhizobial Inoculation and Molybdenum Fertilization in Peanut Crops Grown in a No Tillage System After 20 Years of Pasture

Abstract

Peanut (Arachis hypogea) is an important legume grain consumed by humans and utilized for effective nutrient cycling in a diverse cropping system. Areas that have been cultivated with perennial pasture for decades may have nutritional deficiencies and lack a sufficient population of atmospheric nitrogen-fixing bacteria. Molybdenum is an essential micronutrient that is part of the enzyme nitrogenase contained within symbiotic Bradyrhizobium bacteria, which are responsible for fixing nitrogen in legumes. Our objective was to evaluate the effects of application of Mo at different rates and a rhizobial inoculant on peanut growth characteristics. The experiment was conducted in the 2009/2010 growing season in a no-tillage cropping system following 20-year use as pasture [Urochloa brizantha (Syn. Brachiaria brizantha)]. The experimental design was a randomized complete block with four replicates. The main plots were characterized by peanut inoculation with Bradyrhizobium inoculant or without, and the split plots were characterized by different rates of molybdenum (0, 50, 100, and 200 g ha -1 ) applied to leaves in the form of ammonium molybdate. The nutritional status of plants, nodulation (number of nodules and nodule dry matter per plant), nitrogenase activity, and nitrogenase specific activity were evaluated at 45 and 64 days after emergence (DAE). The yield components and kernel yield were evaluated at the end of the growing season. Nitrogenase enzyme activity at 64 DAE approximately doubled, and the number of pods per plant was greater with inoculation than without, both of which led to greater yields of pods and kernels. In long-term pasture areas, inoculation and molybdenum fertilization greater than the currently recommended rate appear to be necessary to increase pod and kernel yield per hectare of peanut when managed under no-tillage.

Peanut response to co‐inoculation of Bradyrhizobium spp. and Azospirillum brasilense and molybdenum application in sandy soil of the Brazilian Cerrado

“…Crusciol et al. (2018) showed increases in grain yield of 621 kg ha −1 (24%) with foliar application of up to 200 g ha −1 of Mo compared with an unfertilized treatment. In this study, the inconsistent response to the application of Mo between the 2 yr of the experiment may be related to the correction of soil acidity carried out before the implantation of the crop, which may have resulted in greater availability of Mo in the soil.…”

“…On the other hand, significant increases were obtained by Quaggio et al (2004) in response to fertilization with 200 g ha −1 of Mo in a low-pH soil. Crusciol et al (2018) showed increases in grain yield of 621 kg ha −1 (24%) with foliar application of up to 200 g ha −1 of Mo T A B L E 3 Effect of molybdenum application and (co)inoculation of Bradyrhizobium spp. and/or Azospirillum brasilense on final plant stand (FPS), pod number per plant (PNP), grain number per pod (GNP), 100-grain weight (100-G), pod yield (PY) and grain yield (GY) of creeping peanut (Arachis hypogaea L. 'RUNNER IAC 886') grown in sandy soil from the Brazilian Cerrado during the two growing seasons compared with an unfertilized treatment.…”

“…In Brazil, peanut has high potential for use in crop rotation with sugarcane ( Saccharum spp.) or in degraded pastures in an integrated crop–livestock system aimed at recovering the productive potential of forage (Crusciol & Soratto, 2009; Crusciol et al., 2018).…”

“…Therefore, the use of sustainable management practices (e.g., the combined inoculation of microorganisms with different functionalities) and the use of promising genotypes are strategies to obtain high grain yield and profitability in the peanut crop (Crusciol et al., 2018; Santos et al., 2018). In this context, the use of plant growth–promoting rhizobacteria (PGPR) along with inoculation of Bradyrhizobium spp., a species of rhizobia specific for the nodulation of the peanut roots in Brazilian tropical soils (Crusciol et al., 2018), may be a viable technique to improve the efficiency of biological N fixation (BNF), reduce chemical fertilizer‐N use, and increase pod yield of peanuts. The PGPR may promote plant growth by regulating plant hormones, improve nutrition acquisition and symbiotic N fixation, improve siderophore production, and enhance the antioxidant system (Bulegon et al., 2016; Chibeba et al., 2015; Inagaki et al., 2014; Liu, Xing, Ma, Du, & Ma, 2013).…”

“…(rhizobia) have been used by some Brazilian peanut farmers. Crusciol et al (2018) reported positive effects of inoculation with Bradyrhizobium spp. strains (SEMIA 6144) in the growth and grain yield of the peanut crop grown in an agricultural area with 20 yr of pasture.…”