This paper reports the first results of an experiment conducted on the Corumbatai type of soil with pH = 5,3 to study the effect, on the cotton crop, of ground lime-stone, green manure with velvet beans (Stizolobium sp.), and a NPK--fertilizer, these treatments being used single or combined. Liming and planting of velvet beans were carried out in the same years, and during these years the control plots and those which received lime alone were left idle. When cotton occupied the plots, these were halved for the application, or not, of NPK. The experiment was conducted so that velvet beans and cotton were present everv year. Averaging the results obtained in the four years reported (1956-57 to 1959--60), the responses to liming, green-manuring and NPK were respectively + 19. + 19 and +13%- These averages, however, were curtailed by several factors, including the application of NPK to the crops which previously occupied the utilized area and the idle periods during the preparatory stage of the experiment. Effectively, the responses to all of the treatments tended to grow better as the years passed. During the course of the experiment the yields decreased considerably in the untreated plots and, in a smaller degree, in the majority of the differently treated ones; contrarily, they tended to increase in those which received lime + green manure + NPK. The responses to the latter treatment were +38 and +115%. respectively in the averages of the first and second biennial periods.