Quantifying the sensitivity of soil organic matter decomposition (SOM) to global warming is critical for predict future impacts of climate change on soil organic carbon stocks (SOC) and soil respiration, especially in semi‐arid regions such as north‐eastern Brazil, where SOC stocks are naturally small. In this study, the responses of the labile and recalcitrant carbon components and soil respiration dynamics were evaluated in three different soil types and land use systems (native vegetation, cropland and pasture) of the Brazilian semi‐arid region, when submitted to temperature increase. After 169 days of incubation, the results showed that an increase of 5°C generated an average increase in CO2 emission of 12.0%, but which could reach 28.1%. Overall, the labile carbon (LC) in areas of native vegetation showed greater sensitivity to temperature than in cropland areas. It was also observed that recalcitrant carbon (RC) was more sensitive to warming than LC. Our results indicate that Brazil's semi‐arid region presents a substantial vulnerability to global warming, and that the sensitivity of RC and of LC in areas of native vegetation to warming can enhance SOC losses, contributing to positive feedback on climate change, and compromising the productive systems of the region. However, further studies evaluating other types of soil and texture and management systems should be carried out to consolidate the results obtained and to improve the understanding about SOM decomposition in the Brazilian semi‐arid region.

Water is an indispensable resource for the maintenance of life; however, the available volume for consumption has decreased over a period of life, as a result of which, the availability of water that is inferior in quality has increased. In this context, we aimed to evaluate the growth and yield of okra (Santa Cruz cultivar) under different nitrogen rates and irrigation facilities using post-treated domestic wastewater through sand filter with intermittent flow in a Brazilian semiarid region. The experiment was performed in the Pombal region of the Paraíba state, Brazil using a randomized block design with six nitrogen Rates (N 1 = 0, N 2 = 40, N 3 = 80, N 4 = 120, N 5 = 160, and N 6 = 200 kg ha -1 ) and irrigation by using wastewater. The water was added to the treatment with 100% (160 kg ha -1 ) using nitrogen fertilization recommendation and irrigation water supply. The effects of treatments on the growth and production variables of okra plants were evaluated.

Water is a scarce resource in semi-arid regions, therefore, the correct water management is an essential practice. In this research we evaluated the use of nitrogen, phosphorus and treated wastewater on the growth and morphophysiology of eggplants (Solanum melongena L.) in the semi-arid region of Brazil. The experiment was conducted in Pombal, Paraíba, Brazil, using a randomized block design, in a 4 × 4 + 1 factorial scheme: wastewater with four nitrogen doses (N1 = 0.22; N2 = 0.39; N3 = 0.56; and N4 = 0.73 g N dm-3) and four doses of phosphorus (P1 = 0.96; P2 = 1.68; P3 = 2.40; and P4 = 3.12 g P dm-3), and the controls – distilled water fertilized with 0.56 g of N dm-3 and distilled water fertilized with 2.40 g of P dm-3. Each treatment was replicated 4 times. The nitrogen and phosphorous interaction did not influence the growth and physiological aspects of eggplant plants. Excess growing media nitrogen significantly decreased gaseous exchanges of eggplant plants, being found decreased of 4.4 μmol m-2 s-1 the CO2 assimilation.

Wastewater use has become an alternative for agriculture in arid and semi-arid areas due to water scarcity besides providing nutrient for plants. This work aimed to evaluate the effects of the interaction of nitrogen and phosphorus doses associated with wastewater on the growth rate of eggplants in the stages of vegetative growth and beginning of fruiting in the semi-arid of Brazil. The wastewater was previously treated using sand filter with intermittent flow. The experiment consisted of a randomized block design in a 4 × 4 + 1 factorial scheme, with four replications. The factors consisted of four nitrogen doses (N1 = 0.22, N2 = 0.39, N3 = 0.56 and N4 = 0.72 g dm-3 of soil), four doses of phosphorus (P1 = 0, P2 = 1.68, P3 = 2.40 and P4 = 3.12 g dm-3 of soil), both using wastewater, and a control treatment (100% nitrogen and phosphorus using drinking water). The interaction of wastewater with nitrogen and phosphorus doses influenced all growth rates at the vegetative stage, except for the relative number of leaves. We found interaction for the relative rates of stem diameter and number and area of leaves at the beginning of the fruiting stage. Nitrogen and phosphorus doses associated with wastewater were excessive even below the recommendation for eggplant cultivation, however, in the absence of wastewater the plants reduce the growth rates of stem diameter and leaf area in the initial period of the fruiting.

The Brazilian semi-arid region has water restrictions, which justifies the cultivation of cowpea associated with sustainable soil management practices. Thus, the objective of this work was to evaluate the water demand and growth of cowpea under doses of sheep manure in the Cariri region of Paraíba. The experiment was carried out in the municipality of Soledade, Paraíba, using a completely randomized design, testing six doses of sheep manure (D1 = 0%, D2 = 5%, D3 = 10%, D4 = 15%, D5 = 20% and D6 = 25%, m/m) and 4 repetitions, totaling 24 experimental units. Water demand was determined during cultivation and at 10 and 22 days after sowing, the length of the main branch was measured, the leaf area estimated and the root, shoot and total dry mass determined. It was verified that doses of sheep manure increase the water demand and the growth of cowpea in the Cariri region of Paraíba, being recommended the application of a dose of 13.51±1.98% of sheep manure.

Cassava wastewater has high organic load and concentration of nutrients and can cause damage to the environment when discarded indiscriminately. However, the residue can help agricultural production. Therefore, this study aimed to determine the appropriate doses of cassava wastewater to enable the highest production and quality of arugula. The experiment was conducted in a greenhouse, in a completely randomized design, consisting of eight treatments composed of the following doses: D1 = 0, D2 = 6.5, D3 = 13, D4 = 19.5, D5 = 26, D6 = 32.5, D7 = 39 and D8 = 45.5 m3 ha-1 of cassava wastewater with four replicates each. We used the arugula cultivar “Cultivada”, and samples of plant height, fresh matter, and shoot dry matter were performed at 15 and 30 days after emergence. The quality of arugula was evaluated through pH, total soluble solids and titratable total acidity. Cassava wastewater had a significant effect on plant height, fresh matter and dry matter of above ground part, pH and total soluble solids of arugula. However, titratable total acidity was not affected by treatments. Our results show that cassava wastewater is a good alternative fertilizer for arugula cultivation but at proper doses up to 26 m3 ha-1 applied through the crop cycle to avoid the deleterious effect of some nutrients in excess, such as potassium.

Apesar dos impactos ambientais gerados pelos resíduos poluentes da indústria sucroenergética, estudos avaliando essa temática na região Nordeste do Brasil ainda são incipientes. Portanto, objetivou-se com este estudo avaliar os impactos ambientais dos resíduos poluentes produzidos pelas indústrias sucroenergéticas no estado de Alagoas. Foi realizado um levantamento, aplicando-se um questionário em três usinas e uma destilaria autônoma, localizadas no estado de Alagoas. As usinas estão identificadas neste estudo como usinas A, B, C e D. As quatro usinas conduziram a fermentação em batelada alimentada (processo descontínuo alimentado) e possuem dorna pulmão. Duas possuem dornas abertas e duas fermentadores fechados, para recuperação do etanol arrastado pelos gases desprendidos durante a fermentação etanólica. O questionário foi preenchido pelos responsáveis com dados operacionais de cada usina. Foi avaliada a moagem de cana, produção de açúcar, produção de etanol hidratado, produção de etanol anidro, kg de açúcar por tonelada de cana e litros de etanol por tonelada de cana, consumo de ácido sulfúrico e de ciclohexano; água utilizada na lavagem da cana e na lavagem dos gases liberados durante a fermentação. As usinas sucroenergéticas no estado de Alagoas avaliadas neste estudo, que produzem açúcar e etanol, além de outros subprodutos comercializáveis, utiliza métodos e processos produtivos com elevado potencial de impacto ambiental.

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