Root Nodule Preparation as a Low-Cost Inoculant for Cowpea

Widely grown in diverse regions of Brazil, cowpea has high nutritional value, is easily cultivated, and can fix nitrogen (N) symbiotically. Although there are commercial inoculants for cowpea, it is difficult for small producers to acquire them. A nodule preparation is an inexpensive and easily prepared option for small farmers. The aim of this study was to test a nodule preparation as a low-cost inoculant, increasing cowpea seed grain production. Thus, different cowpea cultivars were compared in two locations, the municipalities of Crato and Madalena, both in Ceará. Two field experiments were performed to evaluate gain derived from this inoculation method. The nodule preparation was created from nodules removed from roots of cowpea grown in the experimental locations. The nodules were macerated and added to water, obtaining a liquid (inoculant) that was applied to the seeds. The experiment was conducted following a randomized block design with four replicates and a 4 × 3 factorial arrangement (N sources × cultivars). Results indicate little interaction between the sources of N and the cultivars because only the shoot dry matter (Crato experiment) exhibited interaction between both. The differences provided by the nodule preparation were more notable among cultivars and between the environments, Crato and Madalena. The nodule preparation differed little from the commercial inoculant; they were comparable. However, gain in relation to the zero control also proved to be reduced, indicating little contribution of the nodule preparation to cowpea under the conditions tested.