Rhizobial inoculation and molybdenum fertilization in peanut crops grown in a no tillage system after 20 years of pasture

Authors: CRUSCIOL, CARLOS A. C. - Sao Paulo State University (UNESP); FERRARI NETO, JAYME - Catholic University - Brazil; TSAI, SUI - Sao Paulo State University (UNESP); Franzluebbers, Alan; COSTA, CLAUDIO H. M. - Federal University Of Goias; CASTRO, GUSTAVO S. A. - Embrapa; RIBEIRO, LIVIA - Sao Paulo State University (UNESP); COSTA, NIDIA - Sao Paulo State University (UNESP)

Submitted to: Revista Brasileira De Ciencia Do Solo
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2018
Publication Date: 12/20/2018
Citation: Crusciol, C., Ferrari Neto, J., Tsai, S.M., Franzluebbers, A.J., Costa, C., Castro, G., Ribeiro, L.C., Costa, N.R. 2018. Rhizobial inoculation and molybdenum fertilization in peanut crops grown in a no tillage system after 20 years of pasture. Revista Brasileira De Ciencia Do Solo. 43:e0170399.

Interpretive Summary: Resource-efficient crop production requires that soil biological components be at peak capabilities to transform nutrients and make effective use of embedded investments in field production. Peanut is an important grain legume dependent on biological nitrogen fixation to be most efficient in producing sufficient quantity and quality of high-protein product. A scientist at USDA-ARS in Raleigh, North Carolina collaborated with scientists at Sao Paulo State University, Dom Bosco Catholic University, Federal University of Goias, and EMBRAPA to study the impacts of legume inoculation with Bradyrhizobium and application of molybdenum to stimulate the nitrogen-fixing enzymatic process on a soil that had been under long-term pasture in the Cerrado of Brazil. Activity of the nitrogen-fixing enzyme was greatest two months after plant emergence when inoculated and fertilized at high molybdenum rate. Number of pods per plant was the yield component that most directly influenced pod and kernel yield in the treatments with inoculation. In agricultural areas with pasture for several years, Bradyrhizobium inoculation and molybdenum fertilization with at least ¾ ounce per acre increased yield of pods and kernel in a no-tillage system with large quantity of surface straw. These results will be useful to farmers and extension specialists in sub-tropical environments to increase the sustainability of low-resource-input farming systems.

Technical 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.