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RESUMO -Planting trees is an important way to promote the recovery of degraded areas in the Caatinga region. Experiments (E1, E2, and E3) were conducted in a randomized blocks design, with three, three, and five replicates, respectively. The objectives were to evaluate biomass of the shoots of: a) gliricidia (G) and sabiá (S), as a response to planting density; b) G, S, and neem (N) in competition; c) G, and S in agroforestry. E1 was conducted in split-plots, and planting densities (400, 600, 800, 1000, and 1200 plants ha -1 ) as subplots. E2 consisted of a factorial comprising the following plots: GGG, NGN, SGS, NNN, GNG, SNS, SSS, GSG, NSN (each letter represents a row of plants). E3 was conducted with G and S in agroforestry experiment. The trees were harvested after 54, 42, and 27 months old, in E1, E2 and E3, respectively. In E1, G presented higher green biomass of the stems and leaf at smaller densities than S, but lower green biomass of branches at most densities. The species did not differ for mean stem dry biomass and leaf dry biomass, but G showed higher branch dry biomass at most densities. Higher planting densities increased green and dry biomass of stems, branches, and leaves in S, but decreased those characteristics in G, with the exception of leaf dry mass, which was not influenced by density. In E2, the behavior of each species was identical in plots containing the same or different species. Griricidia showed the highest green biomass of stems and branches, and the highest values for geren biomass of the leaf were observed for gliricidia and neem. The highest stem, branch, and leaf dry biomass values were obtained for G, S, and N, respectively. In E3, G was superior for stem and leaf green biomass, and for stem and branch dry biomass. There were no differences between species for the other biomass values. Palavras-chave: Azadirachta indica; Gliricidia sepium; Mimosa caesalpiniifolia. BIOMASSAS DE ESPÉCIES ARBÓREAS EM RESPOSTA A DENSIDADES DE PLANTIO E À COMPETIÇÃO INTERESPECÍFICA ABSTRACT -Existe interesse na recuperação de áreas degradadas da Caatinga com o plantio de árvores. Experimentos (E1, E2 e E3) foram realizados, em blocos ao acaso com três, três e cinco repetições, respectivamente, para avaliar as biomassas da parte aérea: a) da gliricidia (G) e sabiá (S), em resposta à densidade de plantio; b) da G, S e nim (N) em competição; e c) da G e S em experimento agroflorestal. E1 foi realizado com

Lettuce is a vegetable crop that requires a large supply of nutrients in a readily available form, within a short period of intense vegetative growth. The use of green manuring, with spontaneous species of the Caatinga biome, can quickly increase the organic matter content in the soil, providing nutrients for the crop. Therefore, the objective of this work was to evaluate the agron omic performance and economic profitability of lettuce fertilized with Calotropis procera in single crop under the semi-arid conditions of the state of Rio Grande do Norte, Brazil. The experimental design was a randomized complete block, with four treatments and five replicates. The treatments consisted of four amounts of C. procera biomass incorporated into the soil (10, 25, 40, and 55 t ha-1 of dry matter). The maximum agronomic efficiency of lettuce productivity was obtained for a yield of 18.16 t ha-1 , with 40.29 t ha-1 of C. procera biomass added to the soil. The maximum economic efficiency of lettuce yield was achieved by the net income of AU$3,006.50 (R$7,546.31 ha-1), provided by the production of 17.65 t ha-1 of fresh mass, with 32.20 t ha-1 of C. procera biomass added to the soil. The use of C. procera as a green manure presents agro-economic feasibility for lettuce cultivation in the semi-arid conditions of the Rio Grande do Norte state.

The use of green manures in vegetable crop production systems has increased, but there is still a lack of information about the correct handling of the species for better use by culture. Two field experiments were conducted in Serra Talhada in the semiarid of Pernambuco state, Brazil, to evaluate the effects of amounts of biomass and times of Calotropis procera incorporation into the soil in the agronomic performance of the beetroot 'Early Wonder' in two growing seasons (fall and spring-summer). The experimental design was a randomized block in three replications. The treatments were arranged in a 4 x 4 factorial scheme, with the first factor corresponding to the quantities of C. procera biomass (5.4, 8.8, 12.2, and 15.6 Mg ha -1 on a dry basis) and the second to the times of incorporation into the soil (0, 10, 20, and 30 days before sowing of beetroot). The following characteristics were assessed in the beetroot: plant height, number of leaves per plant, root diameter, total productivity, commercial productivity, and dry mass of roots. The amount of C. procera as well as the time of incorporation and growing season directly influenced the agronomic performance of beetroot. Regardless of the assessed agronomic characteristics, increasing amounts, and decreasing the time of incorporation proportionally influenced the performance of beetroot. The best agronomic performance of the beetroot was obtained by fertilization with 15.6 Mg ha -1 of C. procera. The ideal time of incorporation of green manure coincided with the date of the sowing of beetroot. The cultivation in the fall season resulted in higher total and commercial productivity of beetroots fertilized with C. procera.

The objective of this work was to evaluate the response of sunflower cultivars submitted to increasing levels of phosphate fertilization in two crops. The experimental design was a randomized complete block design with four replicates in subdivided plots, where five doses of simple superphosphate (0, 50, 100, 150, and 200 kg ha-1 P2O5) were allocated to the plots and three sunflower cultivars (Aguará 06, Altis 99, and Embrapa 122-V2000) were assigned to the subplots. The variables evaluated were the P content in the diagnostic leaf, number of achenes per capitulum, achene yield (kg ha-1), oil content (%) and oil yield. The phosphorus doses increased the components of production. The dose that provided the best sunflower performance varied for the different cultivars. Among the doses studied, fertilization with 100 kg ha-1 P2O5 in the 2016 agricultural crop and 150 kg ha-1 P2O5 in the 2017 agricultural crop provided the best conditions for sunflower cultivation. The cultivar Aguará 06 produced more achenes and oil than the other cultivars analyzed in the agricultural crops.