Study of the chemical soil fertility in the biomass bank technology of Pennisetum purpureum Schum cv. CUBA CT-115 with different exploitation years.

The change of chemical fertility of a ferrallitic red brown soil in the biomass bank technology of Pennisetum purpureum Cuba CT-115 was researched with different years of exploitation (6, 12 and 18 years, respectively). The pH indicators (in KCL), MO, N, P, K, Ca and Mg were researched. The data were subjected to variance analysis, according to simple classification model and the t-Student test was used in necessary cases. With the longer time of exploitation of 18 years, there was significant increase (P < 0.0001) of the OM (3.07 to 5.16 %), followed by the biomass bank with 12 years (3.04 to 3.71%), while the P content significantly decreased (P < 0.0056) in the biomass bank of 18 years (57.84 to 39.21 ppm),but did not varied in 12 years. The soil in the biomass bank of 6 years did not showed variation of the studied chemical indicators. The results indicated that there is an increase of the soil OM as it is higher the exploitation time of the biomass bank and P content decrease. It is recommended that, under similar soil conditions, the monitoring of the soil fertility state, mainly of the P assimilable content, from 6 years of uninterrupted exploitation with this technology. [ABSTRACT FROM AUTHOR]