Compost stability, phytotoxicity and nutrient quality as influenced by carbon to nitrogen ratios of feedstock

Effects of three C/N mixes of groundnut husk (GNH) and Wister rat litter (RL) on stability, nutrient quality and phytotoxicity of compost were tested and compared with the conventional carbon and nitrogen feedstock mix on 1:3 w/w modality respectively. The GNH and RL were respectively composted in a windrow at three proportionate levels (14.7+105.3, 39.2+80.8 and 63.7+56.3 kg) to achieve C/N nutrient ratios of 20:1, 30:1 and 40:1 respectively using the Pearson square method. A control pile containing GNH+RL (tagged conv. 1:3) applied at 30 kg GNH and 90 kg RL using the conventional 1:3 w/w modality was compared in triplicate. Data were taken on daily compost temperature, pH, EC and nutrient content of stabilized composts. Phytotoxicity was assessed by using two compost extract concentrations of 100 and 50% per compost. There were three replications laid in CRD. Data were statistically analyzed. Number of days to compost stability was significantly influenced by C/N with values increasing with decreasing C/N in the order of 59 < 69 < 74 < 77 days for 40:1, 30:1, 20:1 and conv. 1:3 respectively. Increasing C/N decreased pH (range of 7.3 – 9.0), EC (range of 1.2 – 2.7dS/m), ash (range of 44.2 – 55.5%), total macronutrient (N+P+K) (range of 3.56 – 5.15%) and calcium content (range of 3.3 – 6.5%) and increased organic C (range of 22.4 – 29.6%) of the resultant composts and GI (range of 25 – 76%) of cowpea. The 100 and 50% concentrations supported higher GI of cowpea in composts produced from lower and higher C/N respectively.

Effect of Compost Extract Addition to Different Types of Fertilizers on Quality at Harvest and Shelf Life of Spinach

Spinach is rich in minerals, vitamins, phytochemicals and bioactive compounds with health-beneficial effects; however, this plant also tends to accumulate oxalates and nitrates in their leaves. Apart from genotype, nutrition is the pre-harvest factor that mostly affects quality attributes at harvest. Particularly, the application of compost extracts (CE) may induce resistance against soil-borne diseases and favour secondary metabolism, increasing antioxidant capacity. The objective of this study was to evaluate the effects of different types of fertilization with or without the addition of CE, on harvest quality and shelf life of minimally processed spinach (Spinacia oleracea, var. Shrike RZ) stored during 12 days at 4 °C. A compost extract (CE) was prepared by mixing a compost from agri-food wastes (vine pruning, leek waste and olive mill waste) with deionized water. CE foliar applications were done from days 28 and 56 after sowing. The treatments applied were: Control; Control + CE; NPK (inorganic NPK fertilizer 15-15-15); NPK + CE; DMPP (ENTEC Nitrofoska® plus the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP)) and DMPP + CE. After harvest, spinach leaves were minimally processed and packaged to generate a passive modified atmosphere. Nitrate content in the control treatment was reduced by the addition of CE, although in the rest of the treatments, CE addition did not produce any effect. For nitrite contents, the lowest value was obtained for the Control + CE. Moreover, the oxalate content was the lowest for the control treatment with a decreasing trend throughout the storage. The treatment Control + CE also showed the highest initial total phenolic contents, with very similar values at the end of shelf life to those observed at harvest for all the treatments. The highest differences in color as regards the initial values were detected for DMPP. Microbial loads increased for all the treatments without differences between them. The atmosphere reached at the end of the cold storage was the same for all the cases, with CO2 and O2 around 10 kPa for each one of them. After 12 days at 4 °C, all the treatments were above the limit of usability, with the spinach leaves acceptable for consumption. The results found in this study indicate that the addition of CE might be convenient for obtaining spinach rich in bioactive compounds and with low concentrations of antinutritional factors, without affecting the microbial load of the final product.

Improving nitrogen fertilizer efficiency with the addition of compost extracts to kailan (Brassica oleracea L.) plants with wick hydroponic cultivation

<p>The goal of this research was to observe the impact of the application of the forms of compost extract and urea fertilizer on the development of kailan plants in the hydroponic wick method. The experiment consisted of a quasi- experimental factorial design with the first element reflecting the compost type: no compost extract, cow manure compost extract, rice straw compost extract, and vermicompost extract. The second element was the use of 0, 100 and 200 kg ha^-1 nitrogen fertilizers. The usage of vermicompost extract shows the maximum growth (59.27 cm), amount of leaves (23.00), overall plant weight (93.92 g plant^-1), canopy weight (61.37 g plant^-1), dried foliage weight (7.17 g plant^-1), fresh root weight (33.40 g plant^-1), leaf greenness (183.80 SPAD) and nutrient uptake (6.32 g plant^-1). (6.32 g plant^-1). The optimal nitrogen fertilizer application was found to be 200 kg ha^-1, which culminated in the maximum plant height (42.18 cm), number of leaves (17.75), overall plant weight (60.42 g plant^-1), leaf greenness (166.23 SPAD) and N uptake (3.73 g plant^-1). With the addition of 100 kg of urea ha^-1, Vermicompost extract achieved the maximum N adhesion strength of 112.05 per cent. The use of vermicompost extract in the production of crops with a hydroponic wick method could fulfill the nutrient requirements of plants.</p>

Impact of mycoinsecticides and abamectin applications on species diversity and abundance of aquatic insects in rice fields of freshwater swamps of South Sumatra, Indonesia

Herlinda S, Alesia M, Susilawati, Irsan C, Hasbi, Suparman, Anggraini E, Arsi. 2020. Impact of mycoinsecticides and abamectin applications on species diversity and abundance of aquatic insects in rice fields of freshwater swamps of South Sumatra, Indonesia. Biodiversitas 21: 3076-3083. Aquatic insects in rice fields generally are predators of rice insect pests. The application of insecticides may reduce the abundance and species diversity of these predators. This study aimed to determine the impact of mycoinsecticides and abamectin application on species diversity and abundance of aquatic insects in rice fields. Mycoinsecticides were made from Beauveria bassiana s.l., Metarhizium anisopliae s.l. and Cordyceps militaris s.l. with carrier from shrimp shell flour compost extract, vegetable oil, and Tween®. The treatments were the mycoinsecticides and abamectin. The results showed there were eight aquatic insects species obtained in this study, i.e. unidentified Dytiscidae, Micronecta sp., Mesovelia sp., Ranatra sp., Anisops sp., Microvelia sp., unidentified species of Veliidae, and Orthetrum sp. belong to 7 families (Dytiscidae, Corixidae, Mesoveliidae, Nepidae, Notonectidae, Veliidae, Libellulidae), and three orders (Coleoptera, Hemiptera, and Odonata). All of the species were predatory insects. The application of mycoinsecticides did not reduce the abundance and species diversity of the aquatic predatory insects, but the application of abamectin reduced the abundance and species diversity of the predators. The highest insect species diversity was in the plots applied with C. militaris s.l., followed by the B. bassiana s.l. and M. anisopliae s.l. plots and the lowest one was found in the abamectin plot. So, the application of mycoinsecticides from B. bassiana s.l., M. anisopliae s.l. and C. militaris s.l. is safe for the aquatic predatory insects and to control rice insect pests than that of abamectin.

Application of Directly Brewed Compost Extract Improves Yield and Quality in Baby Leaf Lettuce Grown Hydroponically

The aim of this work was to study whether the application of a directly brewed compost extract (added in the nutrient solution or by microsprinkler) could be used to improve the yield and quality of baby leaf red lettuce growing in a floating system, and to control the incidence of Pythium irregulare. Its effect on the quality of fresh-cut red lettuce was also studied. For this, two experiments were carried out over two growing cycles (winter–spring and autumn). The results showed that the use of compost extract added to the nutrient solution improved baby leaf lettuce growth and quality, reducing the nitrate content and enhancing the content of potentially health-promoting compounds such as phenols and flavonoids and the antioxidant capacity. Microbial quality was maintained during storage and the compost extract had no negative effect on the microbial load of the final product. In addition, application of the compost decreased the population of P. irregulare in the water. It is concluded that the application of directly brewed compost extract is of potential use in a sustainable soilless production system for baby leaf red lettuce, since it improves the yield and quality of the product and is able to control the incidence of P. irregulare.