Weeds in a soil cultivated with sugar cane with mineral fertilization and green manure

Abstract

 Weeds are capable of producing significant changes in the structure, composition and processes of the agroecosystem, being able to affect the yield of the sugarcane crop by 20-25% or up to 97.5% if the competition for nutrients, water and light is permanent. The tasks carried out for its elimination, manual, mechanical and chemical control, increase production costs. In this sense, the incorporation of green manures is beneficial in favoring weed control, increasing the organic matter of the soil, improving its physical, chemical and biological properties, increasing the availability of nutrients and reducing the use of mineral fertilizers. The aim of the present study was to evaluate the behavior of the community of weeds in sugar cane, seed phase, using Sesbania herbacea as green manure. A randomized complete block design was carried out with three treatments: 1) S. herbacea (AV) green manure alone; 2) NPK nitrogen fertilization (160 60 80) and 3) PK fertilization (00 60 80) + AV, and four repetitions, where weeds were sampled on five dates, with the registered data diversity indices were calculated: richness (S ), diversity (H'), uniformity (E) and value of importance (IVI) of weeds. The highest S values were observed in the month of November in the three treatments, but they were always higher in treatment 2 (NPK); AV and PK+AV showed the lowest values in October and December. H’ varied from low to medium, in all treatments the highest values were observed in the last sampling. E varied from medium to high, highlighting its inverse relationship with S. The values of the diversity indices did not show statistical differences between treatments in the period studied, so it is recommended to do a long-term follow-up. The most important species in the community were C. rotundus, J. tamnifolia, P. niruri and I. triloba.