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It is widely recognized that the input of organic matter in tropical agriculture is essential to maintain productivity and soil quality. This study aimed to investigate the dynamics of organic C pools and CO2 emission influenced by organic compost fertilization and leucaena biomass in an area of 6 years under organic farming. The system consisted of 5 treatments based on 5 levels of fertilization with organic compost (0, 10, 20, 30, and 40 t ha−1). Each block was surrounded by leucaena and their pruning's were distributed in equal proportions for all treatments. Two rotating crops were performed per year, cabbage/corn. Soil samples were collected in the 0–10 and 10–20 cm layers in 2-year seasons. TOC and N stocks were between 23.1 and 51.6 t ha−1, and 2.1 and 5.4 t ha−1, respectively. The highest compost doses increased the microbial biomass C and N. The increase in microbial biomass was followed by higher emissions of C-CO2. Increased microbial quotient values indicated C accumulation in the system by a higher amount of active metabolic C. The microbial biomass was less efficient in the use of the high organic compost doses. The dose of compost should be reduced and applied constantly by the farmers to attend the plant demand by nutrients and increase the efficiency of C sequestration in the soil. This C sequestration will also improve biological activity and soil quality in tropical regions, increasing food production. [ABSTRACT FROM AUTHOR]

The degraded areas in Southern Brazil are undergoing rapid conversion from abandoned fields into agroforestry system. Our focus was to investigate the impact of land use and soil properties on soil fauna and quality in an agroforestry system and a natural ecosystem. The agroforestry system had the presence of Cicadidae (0.1 ind trap−1), Diplura (0.01 ind trap−1), Gryllidae (0.2 ind trap−1), Gyrinidae (0.07 ind trap−1), and Larvae (0.3 ind trap−1), and it presents lower SOC (less 44.3%) and higher total N (more 29.8%) and P contents (more 68.8%) when compared with the natural ecosystem. Richness and diversity declined (less than 16.3 and 31.8%, respectively) with increasing soil pH. Natural ecosystem showed the greatest diversity (H' = 2.44) of soil fauna. A negative correlation was observed between diversity and soil pH (−0.91), and positive correlations among diversity and SOC (0.97), richness (0.88), and dominance (0.93). In conclusion, fauna abundance, precipitation, and soil pH played essential roles in soil quality through ecosystem services, habitat, and energy provision, which in turn promoted the entire soil food web. Thus, the findings in the agroforestry system and natural ecosystem help us to understand how land uses impact soil fauna, and soil quality. [ABSTRACT FROM AUTHOR]

The use of cover crops within olive groves, be they legume, non-legume or a mixture, has become more widespread in recent years as a practice of environmental sustainability to improve soil organic matter. Using both SC: a sole-crop and AC: an alley-cropping, Hordeum vulgare L. and Vicia sativa L. were studied with olive trees 2016 to 2019. The aim was to determine the effects of both of these systems on: TB: total biomass, POXC: Permanganate oxidizable Carbon and SOC: Soil Organic Carbon, TN: Total Nitrogen, C:N ratio; and P: available Phosphorus. These parameters were measured on 192 soil samples collected at 0–20 and 20–40 cm soil depths before planting and after crop harvesting. The results showed that within the relatively short time of three seasons, cover crops increased SOC slightly overall. Compared to the SC, AC limited crop and weed growth and produced significantly less TB, especially in 2017–18, a particularly dry season. This can be explained by the initial state of the soil which was significantly affected by the cropping system. AC enhanced SOC and stabilized the POXC during all three cropping seasons for all treatments. Mixed crop (barley and vetch) significantly increased TN in the AC over the three cropping seasons and decreased the C:N ratio. However, with barley and vetch in pure stand, the mean TN was similar to that of fallow. Also, this type of agroforestry increased the mean available phosphorus with barley, vetch and a mixture of the two compared to fallow. [ABSTRACT FROM AUTHOR]

A detailed study was conducted to investigate the long-term effects of rice–wheat and poplar-based agro-forestry systems existing on a large area for last 25 years on the distribution of macro as well as micronutrients in surface soils, as well as their profiles. To achieve these objectives, profile soil samples (0–150 cm) were collected from 10 randomly scattered locations each from rice–wheat and poplar-based agro-forestry systems and analyzed for various physico-chemical properties. The results of our investigation revealed that pH, EC, OC available N, P and K reported significantly higher levels in agro-forestry as compared to rice–wheat system. On the other hand, DTPA-extractable and total Zn, Cu, Fe and Mn were significantly higher in D1 (0–15 cm), D2 (15–30 cm) and D3 (30–45 cm) depths of rice–wheat system which may be attributed to the reduced conditions prevailing during rice crop. Nutrient budgeting also assessed the impact of crop removal and fertilizer inputs along with recycling of crop residue and leaf litter. Also, the build-up of available nutrient status in surface layer (0–15 cm) and soil profiles (0–150 cm) continuously under these two systems helped in maintaining agricultural sustainability and soil fertility over a long period of time. [ABSTRACT FROM AUTHOR]

This article aims to compare the effects of applying three doses of sewage sludge, with or without liming, on organic matter, total and available chromium (Cr), and their concentration in plants. Unfertilized (NF) and mineral treatments were used as control. Soil organic-matter (SOM) modification depended on the interaction of liming and sewage sludge implementation. Liming, high sludge doses, and mineral treatment caused less SOM in the second year of study. However, after 3 years, SOM was increased by both mineral and sludge fertilizers compared to NF treatments as result of tree development and the reduction of organic-matter mineralization into the soil. These findings could have important implications for soil carbon storage capacity. Total Cr in soil and forage was increased by sewage sludge application compared to mineral or NF treatments. Liming increased Cr availability in the spring of 2000, where sewage sludge was applied, and reduced Fe availability. [ABSTRACT FROM AUTHOR]

Tree species have varied canopy architecture, which influence light interception or quantum of light available to crops grown underneath their canopies. Therefore, it is necessary to understand the growth pattern of different agroforestry tree species so that potential light available to crops under a particular tree is known. The Khasi mandarin (Citrus reticulata) and alder (Alnus nepalensis) show conforming Roux's model of tree architecture. The architecture of pine is similar to Rauh's model. Leaf flushing in alder and Khasi pine (Pinus kesiya) occurs during the months of February and March, while in the case of Khasi mandarin it occurs twice (February and August) in a year. The active shoot growth was observed during February to April in the case of Khasi mandarin and Khasi pine, however, it continued for over four months (February to May) in the case of alder. Leaf fall started during the post-rainy period (October to February) and peaked during the dry winter (January) in Khasi mandarin and alder, but in Khasi pine, it occurred throughout the year with a peak in February. In terms of height growth, the species ranked as Alnus nepalensis> Pinus kesiya> Citrus reticulata, and in terms of growth in diameter (dbh) the order was Pinus kesiya> Alnus nepalensis> Citrus reticulata. The total aboveground biomass was highest in Khasi pine, followed by alder and Khasi mandarin. Bole contributed about 59% to 78% of total aboveground biomass while leaves contributed only about 8% in all the tree species. The fine root biomass in alder and Khasi pine decreased with increase in distance from the tree trunk, but in Khasi mandarin, it showed a reverse trend. The maximum total fine root mass (trees and herbaceous fine root) was recorded in the upper soil layer of Khasi pine-based agroforestry system [ABSTRACT FROM AUTHOR]

Mirids, Sahlbergella singularis, are the most harmful cacao pest in Africa. Chemical management, although controversial, is currently the only effective option for controlling these pests. Based on in vitro and field experiments, this study evaluated and compared the effectiveness of aqueous extracts obtained from the seeds of Thevetia peruviana (TP) and Azadirachta indica (AI) in controlling cocoa mirids, S. singularis. Thevetia peruviana extracts proved to be more effective than A. indica extracts and were as effective as Actara 25 WG, the benchmark insecticide, in reducing mirids in the field. All the aqueous extracts tested in vitro displayed insecticidal activities within maximum eight days and some repellent effects at both 10 and 25% w/v. Treatment of mirid food with the extracts also led to high mortality rates and to significant avoidance of pods treated with the TP25, TP10 and AI25%. The use of plant aqueous extracts to control mirids in the field thus offers promising prospects for the control of this pest, given the availability of the plants, their simple preparation, their effectiveness and their eco-friendly features. [ABSTRACT FROM AUTHOR]