Soil ionomic and enzymatic responses and correlations to fertilizations amended with and without organic fertilizer in long-term experiments

Responses of soil enzymatic activities and microbial biomass phosphorus to improve nutrient accumulation abilities in leguminous species

Fertilizers application are widely used to get a higher yield in agricultural fields. Nutrient management can be improved by cultivating leguminous species in order to obtain a better understanding of the mechanisms that increase the amount of available phosphorus (P) and potassium (K) through fertilizer treatments. A pot experiment was conducted to identify the leguminous species (i.e., chickpea and pea) under various fertilizer treatments. Experimental design is as follows: T0 (control: no fertilizer was applied), T1: P applied at the level of (90 kg ha-1), T2: (K applied at the level of 90 kg ha-1), and T3: (PK applied both at 90 kg ha-1). All fertilizer treatments significantly (p < 0.05) improved the nutrient accumulation abilities and enzymes activities. The T3 treatment showed highest N uptake in chickpea was 37.0%, compared to T0. While T3 developed greater N uptake in pea by 151.4% than the control. However, T3 treatment also increased microbial biomass phosphorus in both species i.e., 95.7% and 81.5% in chickpeas and peas, respectively, compared to T0 treatment. In chickpeas, T1 treatment stimulated NAGase activities by 52.4%, and T2 developed URase activities by 50.1% higher than control. In contrast, T3 treatment enhanced both BGase and Phase enzyme activities, i.e., 55.8% and 33.9%, respectively, compared to the T0 treatment. Only the T3 treatment improved the activities of enzymes in the pea species (i.e., BGase was 149.7%, URase was 111.9%, Phase was 81.1%, and NAGase was 70.0%) compared to the control. Therefore, adding combined P and K fertilizer applications to the soil can increase the activity of enzymes in both legume species, and changes in microbial biomass P and soil nutrient availability make it easier for plants to uptake the nutrients.

Determining the extraction conditions and phytotoxicity threshold for compost maturity evaluation using the seed germination index method

The phytotoxicity of the compost aqueous extracts determines the maturity. To improve the accuracy of compost maturity evaluation using the seed germination index (GI) method, different extraction methods (different moisture content and extraction ratio) were designed to obtain samples with various phytotoxic level. This study analyzed the effects of different extraction condition of compost samples on GI, and established the relationship between phytotoxicity and GI. The results showed that the moisture content and extraction ratio of the compost significantly affected the GI. The extraction ratio for the compost with 60-70 % moisture content was 1:10 (ratio of compost mass to extract volume). However, commercial compost, which must have a moisture content of 30-45 %, had an extraction ratio of 1:30 (w:v). More importantly, compost extraction based on dry weight, with a moisture content of 10-15 %, more effectively reflected the phytotoxicity variations during composting. In such cases, the extraction ratio should be at least 1:30 (w:v) but not exceed 1:50 (w:v). The relationship between phytotoxicity and GI showed that dissolved organic carbon and dissolved nitrogen were the most important factors influencing GI, followed by NH4+, electrical conductivity, K, volatile fatty acids, Zn, and Cu. For composts with a GI greater than 70 %, the dissolved organic carbon, dissolved nitrogen, and NH4+ concentrations were below 257, 164, and 73 mg/L, respectively. These findings provide an optimized standard method for compost maturity evaluation using GI and a concentration threshold of key phytotoxicity is proposed to achieve accurate control of compost maturity.

Modified plant architecture integrated with liquid fertilizers improves fruit productivity and quality of tomato in North West Himalaya, India

India produces around 19.0 million tonnes of tomatoes annually, which is insufficient to meet the ever-increasing demand. A big gap of tomato productivity (72.14 t ha^-1) between India (24.66 t ha^-1) and the USA (96.8 t ha^-1) exist, which can be bridged by integrating trellis system of shoot training, shoot pruning, liquid fertilizers, farmyard manure, and mulching technologies. Therefore, the present experiment was conducted on tomato (cv. Himsona) during 2019-2020 at farmers' fields to improve tomato productivity and quality. There were five treatments laid in a randomized block design (RBD) with three replications; T₁ [Farmer practice on the flatbed with RDF @ N₁₂₀:P₆₀:K₆₀ + FYM @6.0 t ha^-1 without mulch], T₂ [T₁ + Polythene mulch (50 microns)], T₃ [Tomato plants grown on the raised bed with polythene mulch + FYM @ 8.0 t ha^-1 + Single shoot trellis system + Side shoot pruning + Liquid Fertilizer (LF₁-N₁₉:P₁₉:K₁₉) @ 2.0 g l^-1 for vegetative growth + Liquid Fertilizer (LF₂-N₀: P₅₂: K₃₄) @ 1.5 g l^-1 for improving fruit quality], T₄ [Tomato plants grown on the raised bed with polythene mulch + FYM @ 8.0 t ha^-1 + Single shoot trellis system + Side shoot pruning + LF₁ @ 4.0 g l^-1 + LF₂ @ 3.0 g l^-1], and T₅ [Tomato plants grown on the raised bed with polythene mulch + FYM @ 10.0 t ha^-1 + Single shoot trellis system + Side shoot pruning + LF₁ @ 6.0 g l^-1 + LF₂ @ 4.5 g l^-1]. The results revealed that tomato plant grown on the raised beds with polythene mulch, shoot pruning, trellising, liquid fertilizers, and farmyard manure (i.e., T₅) recorded higher shoot length, dry matter content, and tomato productivity by 20.75-141.21, 18.79-169.4, and 18.89-160.87% as compared to T₄-T₁ treatments, respectively. The T₅ treatment also recorded the highest water productivity (28.39 kg m^-3), improved fruit qualities, net return (10,751 USD ha^-1), benefit-cost ratio (3.08), microbial population, and enzymatic activities as compared to other treatments. The ranking and hierarchical clustering of treatments confirmed the superiority of the T₅ treatment over all other treatments.

Bio-inherent attributes of water hyacinth procured from contaminated water body-effect of its compost on seed germination and radicle growth

Compost is generally used for soil conditioning, growing plants and remediation of pollution. It is imperative to evaluate compost standard and toxicity test is a salient parameter for determining compost quality. Seed germination test is an essential method to discern the phytotoxicity of compost. Ecotoxicity of water hyacinth compost was inspected for the denouement of the compost quintessence and its concentration on seed germination indices. The aim of this paper was to assess seed emergence rate index, germination velocity coefficient and rate of germination of L. esculentum and B. oleracea at discrete concentrations of water hyacinth compost. The highest germination percentage achieved was 95% (L. esculentum) at 100 g/L and 100% (B. oleracea) at 32 g/L of the compost extract. The probability of inadvertent ceasing of germination was found to be < 0.0001 for either of the test species. Consequently, the water hyacinth compost aid plant growth and is recommended for substantially ameliorating languishing ecological idiosyncrasy.

Distribution, contamination and accumulation of heavy metals in water, sediments, and freshwater shellfish from Liuyang River, Southern China

Heavy metal distributions in water, sediments, and freshwater shellfish collected from Liuyang River in China have been investigated. The concentrations of heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were determined by ICP-MS. The distribution pattern of heavy metals in sediments was different from that in water. Large coefficients of variation of heavy metal concentrations were observed in water due to the susceptibility to discharge fluctuation and seasonal variation. Multivariate statistical analysis such as Pearson's correlation analysis, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were employed to identify the possible sources of heavy metals in sediments. These heavy metals were categorized into three distinct groups, one was derived from natural existence and two were associated with anthropogenic activities. Five shellfish species including three species of gastropod mollusks (Parafossarulus eximius, Semisulcospira cancellata, and Pomacea canaliculata) and two species of bivalve mollusks (Corbicula fluminea and Anodonta woodiana) were collected and investigated. The distribution pattern of heavy metals in shellfish species was visualized by the nonmetric multidimensional scaling (NMDS) plot. The metal pollution index (MPI) values for the shellfish species were in the descending order of C. fluminea > A. woodiana > S. cancellata > P. eximius > P. canaliculata.

Seed germination test for toxicity evaluation of compost: Its roles, problems and prospects

Compost is commonly used for the growth of plants and the remediation of environmental pollution. It is important to evaluate the quality of compost and seed germination test is a powerful tool to examine the toxicity of compost, which is the most important aspect of the quality. Now the test is widely adopted, but the main problem is that the test results vary with different methods and seed species, which limits the development and application of it. The standardization of methods and the modelization of seeds can contribute to solving the problem. Additionally, according to the probabilistic theory of seed germination, the error caused by the analysis and judgment methods of the test results can be reduced. Here, we reviewed the roles, problems and prospects of the seed germination test in the studies of compost.

Variations in eco-enzymatic stoichiometric and microbial characteristics in paddy soil as affected by long-term integrated organic-inorganic fertilization

To investigate the effects of different nutrient management regimes on the soil chemical, eco-enzymatic stoichiometric and microbial characteristics, soil samples were collected from a 30-year, long-term field experiment with six plots growing rice. The results showed that as integrated fertilization increased, so did the concentrations of soil total or available nutrients and microbial biomass carbon (MBC). Our results also found enhanced soil basal respiration and cumulative carbon mineralization compared to chemical fertilization alone at the same nutrient doses. The activities of soil protease (Pro), β-glucosidase (βG), N-acetyl-glucosaminidase (NAG) and acid phosphatase (AP) from the integrated fertilization treatments were significantly higher than those of the treatments without organic manure, so did the activities of soil leucyl aminopeptidase (LAP) and urease (Ure) from the treatment with organic manure in addition to farmer practise fertilization (NPKM2). The stoichiometric ratios, expressed as lnβG/ln(NAG+LAP)/lnPro/lnUre/lnAP, ranged from 1:0.94:1.04:0.67:1.01 to 1:0.98:1.10:0.78:1.25, indicating that the acquisition of C, N and P changed consistently and synchronously under different nutrient management strategies. Integrated fertilization was more beneficial to the acquisition and utilization of soil organic carbon compared to low-molecular-weight organic nitrogen. We concluded that protease and urease should be considered in eco-enzymatic stoichiometric assessments for the hydrolysis of proteins, amino acids, carbohydrates and phosphomonoesters in soil, and integrated fertilization with chemical fertilizers and organic manure should be recommended as a preferable nutrient management system for intensive rice cultivation.

Variations in nutrient and trace element composition of rice in an organic rice-frog coculture system

Introducing frogs into paddy fields can control pests and diseases, and organic farming can improve soil fertility and rice growth. The aim of this 2-year field study was compare the yield and elemental composition of rice between an organic farming system including frogs (ORF) and a conventional rice culture system (CR). The grain yields were almost the same in the ORF system and the CR system. The ORF significantly increased the contents of phosphorus (P), ion (Fe), zinc (Zn), molybdenum (Mo) and selenium (Se) in rice grain at one or both years. However, the ORF system decreased the calcium (Ca) content in grice grains, and increased the concentration of cadmium, which is potentially toxic. A principal components analysis showed the main impacts of ORF agro-ecosystem on the rice grain ionome was to increase the concentration of P and trace metal(loid)s. The results showed that the ORF system is an ecologically, friendly strategy to avoid excessive use of chemical fertilizers, herbicides and pesticides without decreasing yields, and to improve the nutritional status of rice by increasing the micronutrient contents. The potential risks of increasing Cd contents in rice grain should be addressed if this cultivation pattern is used in the long term.

Nutrient and toxic element soil concentrations during repeated mineral and compost fertilization treatments in a Mediterranean agricultural soil

Agricultural soils of semi-arid Mediterranean areas are often subjected to depletion of their chemical, physical, and biological properties. In this context, organic fertilization, in addition to providing nutrients for a longer time in respect to mineral fertilization, improves many other characteristics related to soil fertility. Moreover, the combined use of organic and mineral fertilizers may promote a more sustainable crop production. However, a concern on the long-term use of organic fertilizers arises in relation to the possible accumulation of toxic elements in soil and their transfer to human beings. For this reason, a long-term study on nutrient and toxic element total concentrations and availabilities during fertilization treatments was carried out. In particular, mineral NPK fertilized soils, soils amended with biowaste compost, soils amended with biowaste compost plus mineral nitrogen, and unfertilized soils were analyzed for 11 chemical elements. The results highlighted that temporal variations in total and bioavailable concentrations of both nutrients and toxic elements, occurring also in unfertilized soils, are wider than those related to fertilization treatments. Anyway, soil amendments with biowaste compost, alone or in combination with mineral fertilizers, reduce Cu bioavailability but improve K, Fe, Mn, and Zn availabilities, excluding at the same time a long-term accumulation in soil. Total and bioavailable toxic element concentrations (apart from available Cd) do not vary in relation to fertilization treatments.