Leaching of phosphorus fertilizer from loose-structured subtropical soils is a major course of agricultural water pollution in southeastern USA. Soil amendments play a major role in the phosphorus retention in soil through different mechanisms. In the present study we tested the effect of two soil amendments; biochar and coal fly ash in immobilizing the soluble phosphorus fertilizer added to sandy Ultisol soils from subtropical USA. Column leaching tests were conducted with Ultisol soil added with biochar (from avocado branch cut biomass) and coal fly ash at 5 tons/ha rate, under simulated rainfall, to collect the leachate over five pore volumes. The leachate was analyzed for the phosphate phosphorus content. In the end, the soil columns were carefully extracted, sectioned and analyzed for the total phosphorus, after acid digestion. Results showed 50% and 6% drop of soluble phosphorus leaching loss in biochar and coal fly ash added soil respectively. Soil amendments have shifted the loosely bound phosphorus into the Ca/Mg bound and Al/Fe/Mn bound pools which are not readily water extractable. Addition of biochar and coal fly ash together showed a synergistic interaction effect in reducing the leaching loss of phosphorus which needs further investigation to understand the exact mechanism.

The present investigation aims to evaluate the feasibility of using Persea americana (Avocado) biodiesel in compression ignition engines. Persea americana bio-oil was extracted through a soxhlet extraction process using n-hexane solvent after careful pre-processing of the feedstocks. Since the Free Fatty Acid content was 1.78% estimated through titration, single stage base-catalyzed transesterification technique was adopted using methanol and sodium hydroxide as catalysts in the molar ratio of 1:6. Gas Chromatography-Mass Spectrometry analysis revealed the presence of Oleic acid in major proportions. The Fourier transform Infra-Red analysis confirmed the presence of carbonyl group ester ions between 722.19 cm-1 and 1460 cm-1. The 13C NMR and 1H NMR studies supported the successful transformation of triglycerides into Fatty Acid Methyl Esters with distinct peaks at 3.369 ppm and 48.147 ppm, respectively.

The treatment of colored effluents containing Procion Red dye (PR) was investigated using H₂SO₄ and HNO₃ modified avocado shells (Persea americana) as adsorbents. The adsorbent materials (AS–H₂SO₄ and AS–HNO₃) were properly characterized. The adsorption study was carried out considering the effects of adsorbent dosage and pH. Kinetic, equilibrium, and thermodynamic aspects were also evaluated. Finally, the adsorbents were tested to treat simulated dye house effluents. For both materials, the adsorption was favored using 0.300 g L⁻¹ of adsorbent at pH 6.5, where, more than 90% of PR was removed from the solution. General order model was able to explain the adsorption kinetics for both adsorbents. The Sips model was adequate to represent the isotherm data, being the maximum adsorption capacities of 167.0 and 212.6 mg g⁻¹ for AS–H₂SO₄ and AS–HNO₃, respectively. The adsorption processes were thermodynamically spontaneous, favorable (− 17.0 < ΔG ⁰ < − 13.2 kJ mol⁻¹), and exothermic (ΔH ⁰ values of − 29 and − 55 kJ mol⁻¹). AS–H₂SO₄ and AS–HNO₃ were adequate to treat dye house effluents, attaining color removal percentages of 82 and 75%. Avocado shells, after a simple acid treatment, can be a low-cost option to treat colored effluents.

Fruit processing waste, such as kernels (endocarp + seed) of avocado [Persea americana Mill. (Lauraceae)], could be used as raw material in the preparation of botanical insecticides. In light of this potential, this study assessed the insecticidal action of extracts and fractions from kernels of two avocado cultivars (Breda and Margarida) on Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B, an important pest species in tropical conditions. Ethanolic and aqueous extracts prepared from kernels of P. americana, regardless of the plant cultivar used, caused promising insecticidal activity to whitefly nymphs. Based on yield in crude extracts [10.32 and 9.85% (w/w), respectively, for cultivars Breda and Margarida], on the bioassay results with crude extracts and on the chemical profiles, the ethanolic extract of kernels of P. americana cv. Breda was chose for the continuation of the study. Thus, the ethanolic extract of kernels of cv. Breda (LC₅₀ = 197.84 ppm and LC₉₀ = 567.19 ppm) was selected and subjected to fractionation by the liquid-liquid partition technique. The hexane and dichloromethane fractions of this extract caused significant mortality of nymphs. The analysis using the ultraviolet (UV) and hydrogen nuclear magnetic resonance (¹H NMR) showed the presence of long-chain aliphatic compounds (alkanols or acetogenins of Lauraceae), alkylfurans (or avocadofurans), and unsaturated fatty acids in these fractions, which are possibly related to bioactivity observed in B. tabaci, besides saccharides. The results show that kernels of P. americana are promising sources of compounds with insecticidal action for the control of B. tabaci biotype B, a great opportunity to transform environmental problems into eco-friendly solutions to agriculture.