Cowpeas (Vigna unguiculata L. Walp) are an economically and socially important legume in northern and north-eastern Brazil and can establish effective symbiosis with nitrogen-fixing bacteria. We evaluated the symbiotic compatibility and efficiency of rhizobial strains from Pernambuco semi-arid soils and determined their symbiotic stability on the IPA-206, BR 17-Gurguéia, and BRS Novaera cultivars, selected for different environments. The experiment was conducted in a greenhouse to evaluate a 3 × 28 factorial arrangement (cultivars selected for different environments × inoculation with the currently recommended strain, uninoculated plants with or without mineral nitrogen, and 25 rhizobial strains from semi-arid soils) in a randomized block design with four replicates. We determined nodule number, shoot and root dry matter, nodule dry matter by nodule number, nitrogen accumulated in the shoot by nodule dry matter, nitrogen content and accumulation in the shoot, relative efficiency of the recommended strain based on nitrogen accumulation, and shoot dry matter. Overall, the cultivars responded differently to different strains and cultivar biological nitrogen fixation potential. Strains G7.85 and BR 3262 showed potential for biological nitrogen fixation. BR 3262 was confirmed to be adequate for inoculation of different cowpea cultivars.

K (cmol c dm-3) 0,3±0,2 0,15±0,12 Na (cmol c dm-3) 0,4±0,2 0,08±0,1 Ca(cmol c dm-3) 14,4±4,8 1,9±1,3 Mg(cmol c dm-3

The great expansion of sugar cane production to non-traditional regions in Brazil has demonstrated the importance of knowledge on the growth characteristics to maintain the productivity and sustainability of the sector. Among the alternatives available to evaluate different varieties of sugar cane, the growth analysis has been one of the most used tools. The objective of this study was to evaluate the growth and development of three varieties of sugar cane for the Pre-Amazon region of Brazil. The varieties used were RB 867515, RB 863129 and RB 92579, and the following parameters of growth were evaluated: accumulation of biomass on the part area, leaf area, number of plants, height of stems, the nitrogen content in different parts of the plant (stem and leaf +3), brix and productivity. For that, samples were collected at 60, 120, 180, 240 and 300 days after planting. For all collecting dates and at 300 days after planting the variety RB 863129 presented better results (P<0.05) for plant height, stem dry weight, N content in leaf +3 and final yield compared to the varieties RB92579 and RB 867515. There was no difference for number of plants (P>0.05) for the varieties RB 863129 and RB 92579. Leaf area was greater (P<0.05) for the variety RB 867515; and nitrogen content of stems were greater for the variety RB 92579 at 300 days after planting. Overall, the RB 863129 variety was the most promising for cultivation in this region during the sugarcane-plant season.