Organic Amendments Effects on Nutrient Uptake, Secondary Metabolites, and Antioxidant Properties of Melastoma malabathricum L.

Amelioration of soil acidity can boost soil fertility, hence increasing nutrient uptake, secondary metabolite, and its antioxidant potential. In the present study, the effectiveness of food waste compost and palm kernel biochar was assessed as soil amendments for Melastoma malabathricum L. grown in acidic soil conditions. A six-month greenhouse study was conducted using completely randomized design (CRD) with three treatment groups, including control plants (T1), plants amended with palm kernel biochar (T2), and plants amended with food waste compost (T3). Data analysis revealed that Melastoma malabathricum L. amended with T3 recorded the highest total chlorophyll content (433.678 ± 13.224 µg g−1 DW), followed by T2 and T1. The increase in chlorophyll content was contributed by the increase in soil pH. This was shown by the positive significant correlations between soil pH and chlorophyll a (r2 = 0.96; p ≤ 0.01) and chlorophyll b (r2 = 0.778; p ≤ 0.01). In addition, the same treatment exhibited the highest total anthocyanin content (leaves; 36.1 × 10−2 ± 0.034 mg/g DW and root extract; 8.9 × 10−2 ± 0.020 mg/g DW), total phenolic content (stem extract; 4930.956 ± 16.025 mg GAE/g DE), and total flavonoid content (stem extract; 209.984 ± 0.572 mg QE/g DE). Moreover, this study also found that the highest antioxidant potential against 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals was exhibited by samples supplemented with food waste compost (T3), followed by palm kernel biochar (T2). This indicates that the soil amendments have the capacity to enhance the secondary metabolites that protect plants, therefore ameliorating Melastoma malabathricum L.’s response towards acidic stress, and resulting in better antioxidant properties. Furthermore, this study also recorded better nutrient uptake in T3. With the significantly higher levels of macronutrient in the soil, the food waste compost could enhance the nutrient properties, secondary metabolites, and antioxidant capacity of Melastoma malabathricum L. grown in acidic soil conditions.

Mixing Sodium-Chloride-Rich Food Waste Compost with Livestock Manure Composts Enhanced the Agronomic Performance of Leaf Lettuce

Food waste generated at the consumer level constitutes a gigantic portion of the total amount of food wasted/lost and valorisation is touted as the most sustainable way of managing the generated waste. While food waste valorisation encompasses several methods, composting is the cheapest technique that can produce stabilised carbon-rich soil amendments. The food waste generated at the consumer level, however, is laden with sodium chloride. The compost produced from such waste has the potential of inducing saline and or sodic conditions in the soil, resultantly impeding proper crop growth and yield. Due to the scarcity of plausible means of eradicating sodium chloride from the food waste before composting, the idea of mixing the composted food waste with other low sodium chloride-containing composts to produce a food waste compost-containing amalgam with a high fertiliser potential was mulled in this study. The study then assessed the effects of mixing sodium-chloride-rich food waste compost with the nutritious and low sodium chloride-containing livestock manure composts on the yield and quality of leaf lettuce. Mixing food waste compost with livestock manure composts in the right proportions created mixed composts that produced a higher lettuce yield than both the pure livestock manure composts and food waste compost. The mixed composts also produced leaf lettuce with higher chlorophyll content and, thus, better marketability and lower nitrate content (with higher health value) than the pure livestock manure composts.

Influence of Recycled Waste Compost on Soil Food Webs, Nutrient Cycling and Tree Growth in a Young Almond Orchard

Composting is an effective strategy to process agricultural and urban waste into forms that may be beneficial to crops. The objectives of this orchard field study were to characterize how a dairy manure compost and a food waste compost influenced: (1) soil nitrogen and carbon pools, (2) bacterial and nematode soil food webs and (3) tree growth and leaf N. The effects of composts were compared with fertilized and unfertilized control plots over two years in a newly planted almond orchard. Both dairy manure compost and food waste compost increased soil organic matter pools, as well as soil nitrate and ammonium at certain time points. Both composts also distinctly altered bacterial communities after application, specifically those groups with carbon degrading potential, and increased populations of bacterial feeding nematodes, although in different timeframes. Unique correlations were observed between nematode and bacterial groups within compost treatments that were not present in controls. Food waste compost increased trunk diameters compared to controls and had greater relative abundance of herbivorous root tip feeding nematodes. Results suggest that recycled waste composts contribute to biologically based nitrogen cycling and can increase tree growth, mainly within the first year after application.

Deciphering the Effects of Waste Amendments on Particulate Organic Carbon and Soil C-Mineralization Dynamics

It is important to understand the dynamics of soil carbon to study the effects of waste amendment inputs on soil organic carbon decomposition. The aim of this study was to evaluate the effect of waste amendment carbon input on the soil organic carbon (SOC) content, soil particulate organic carbon (POC) content and soil organic carbon mineralization rate dynamics. A 60-day experiment was carried out in the laboratory. The following treatments were compared: (1) CK: soil without amendments; (2) FW1: soil with food waste compost (soil/food waste compost = 100:1); (3) FW2: soil with food waste compost (soil/food waste compost = 100:2); (4) GW1: soil with garden waste compost (soil/garden waste compost = 100:0.84); (5) GW2: soil with garden waste compost (soil/garden waste compost = 100:1.67); (6) FGW1: soil amendments mixture (soil/food waste compost/garden waste compost = 100:0.5:0.42); (7) FGW2: soil amendments mixture (soil/food waste compost/garden waste compost = 100:1:0.84); the inputs of amendment carbon to FW1, GW1 and FGW1 were 2.92 g kg−1, the inputs of amendment carbon to FW2, GW2 and FGW2 were 5.84 g kg−1. The results showed that the addition of waste amendments increased the amount of cumulative mineralization from 95% to 262% and accelerated the rate of soil mineralization. After adding organic materials, the change in the soil organic carbon mineralization rate could be divided into two stages: the fast stage and the slow stage. The dividing point of the two stages was approximately 10 days. When equal amounts of waste amendment carbon were input to the soil, there was no significant difference in SOC between food waste and garden waste. However, SOC increased with the amount of amendment addition. However, for POC, there was no significant difference between the different amounts of carbon input to the garden waste compost treatments. SOC and POC were significantly correlated with the cumulative emissions of CO2.