Cesar Crispim Vilar

Weed mapping using techniques of precision agriculture

The aim of this study was to identify and map the weed population in a no-tillage area. Geostatistical techniques were used in the mapping in order to assess this information as a tool for the localized application of herbicides. The area of study is 58.08 hectares wide and was sampled in a fixed square grid (which point spaced 50 m, 232 points) using a GPS receiver. In each point the weeds species and population were analyzed in a square with a 0.25 m2 fixed area. The species Ipomoea grandifolia, Gnaphalium spicatum, Richardia spp. and Emilia sonchifolia have presented no spatial dependence. However, the species Conyza spp., C. echinatus and E. indica have shown a spatial correlation. Among the models tested, the spherical model has shown had a better fit for Conyza spp. and Eleusine indica and the Gaussian model for Cenchrus echinatus. The three species have a clumped spatial distribution. The mapping of weeds can be a tool for localized control, making herbicide use more rational, effective and economical.

Biochar no manejo de nitrogênio e fósforo para a produção de mudas de angico

The objective of this work was to evaluate the effect of biochar applied together with the macronutrients N and P, for the formation of substrate, on the growing of angico (Anadenanthera colubrina) seedlings for forest restoration. The experiments were conducted in a forest nursery, in a completely randomized block design. Interactions were studied between increasing concentrations of biochar and of N as urea, and between concentrations of biochar and P as superphosphate, added to a Yellow Oxisol. Seedling patterns of growth, quality, and nutrition were determined, and the results were subjected to the study of polynomial regression (response surface). The interaction between biochar and N favored leaf nutrition and leaf-concentration of Mg of angico seedlings; however, it did not influence plant growth. Angico seedlings subjected to the application of biochar and P showed higher nutrition and nutrient use efficiency of Ca and K. Biochar application with N and P to the substrate shows potential for the production of quality seedlings, which favors the success of practices for forest restoration in regions with low soil fertility and subjected to water stress periods.