Field Evaluation of Extensive Crops Inoculated with Azospirillum sp.

Abstract

The available information about the changes in growth and production of extensive crops due to the inoculation with formulations containing Azospirillum sp. is abundant. The crop responses to the presence of Azospirillum sp. are generally related with changes in their growth during early stages of development. It leads to variable contributions to the final grain production depending on the differences in the occurrence of abiotic stresses (i.e., water and nutrient uptake). We present, based on recently available articles, the design of field trials and its analysis for describing the value of the inoculation practice in terms of grain production as a tool to support crop management decisions. The ecophysiological responses require the interpretation of the results based on the frequency of their occurrence as well as the discrimination among hierarchical productivity factors (i.e., spatial and temporal variability). Because of the variability in the crop responses to the inoculation with Azospirillum sp., a large number of observations are needed to describe significant differences between treatments. In the case of rainfed wheat (Triticum aestivum L.) crops from the semiarid pampas (Argentina), the range can vary between 60 in seasons with normal rainfall patterns and almost 200 cases in dry seasons. The analysis of distribution response values is a more realistic approach to measure the crop performance to inoculation under the interaction of complex random factors and provides also a probabilistic answer to stakeholders. For example, based on the distribution of maize (Zea mays L.) responses to Azospirillum sp. from 316 cases located in the pampas region of Argentina it was observed that in more than 81.1 % of the cases the incremental revenue of the practice exceeded its cost and it could be included as a crop management practice under the current production conditions.