The efficiency in the use of nitrogen (N) and potassium (K) may be severely limited in soils with high rates of nutrient loss and that also tend to harden and restrict root growth. The choice of legume residues should take into account the nutrient supply and the need for soil improvement. We assessed the capacity of alley cropping systems to enhance root development, increase nutrient uptake and improve the use of N and K in maize. The experiment included six treatments with residues of four perennial Fabaceae: Clitoria + Gliricidia (C + G); Acacia + Gliricidia (A + G); Leucaena +Gliricidia (L + G); Leucaena + Clitoria (L + C); Leucaena + Acacia (L + A) and a control without legumes. We determined chemical and physical indicators, root length density (RLD) and an efficiency index. The results demonstrate the effects of amending soils with N and K with root growth constrained by hard‐setting. The application of combined residues improved the physical properties of hard‐setting soils and increased basic cations in the topsoil. A combination of residues with N and K fertilizer increased the maize yield. The relative efficiency and RLD in the L + A treatments were highest as a result of increased application through the residues containing N and K. The choice of residues for hard‐setting soils should take into account the supply of nutrients as well as the improvement of soil properties.

Produced waters are complex mixtures which contain a large number of contaminants including finely dispersed oil, metals, and gases such as H2S and CO2, that are originated from oil and natural gas. This work examines the use of solvent extraction to recover sulphides. It tested three commercial alkylamines as extractants, which were dissolved in aviation kerosene (JET FUEL). In this research, real samples of produced water from the oil industry with initial concentration of 0.660 mg/L H2S were used. The parameters studied were: Amine/JET FUEL ratio (0.25 v/v) and Organic/Aqueous Phase ratio (1/3 v/v). After the tests, it was concluded that the highest extraction efficiency occurred with the amine DUOMEEN ® O, which removed 76% of sulfides, followed by the ARQUAD ® 2C-75, yielding 59% in sulfide removal, and the DUOMMEN ® T, which removed as much as 40% of sulfides.

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