Emerging technology effects on combined agricultural and eco-vermicompost.

This study focused on the waste management of livestock manure and wetland plant residues and their increasing effect on terrestrial and aquatic ecosystems. The benefits of nutrient-rich plants and manures are often overlooked. By conducting a soil column experiment with a fully factorial design, this work found that adding the vermicompost amendments of wetland plants [combination of Canna indica (CiV), Cyperus alternifollius (CaV), Acorus calamus (AcV), and Hydrocotyle vulgaris (HvV) vermicompost] to agricultural wastes affected maize growth throughout its growing season. The results demonstrated that the use of combined AcV and HvV wetland plant-based vermicompost as an organic fertilizer increased the plant total nitrogen (TN: 92% increase) and soil organic matter (SOM: 192% increase) compared with those in control CK. Meanwhile, the combination of CaV with HvV increased the shoot biomass by 3.4 and 4.6 folds compared with that in NPK and CK, respectively. Overall, a new approach for transforming ecological wastes into organic fertilizers was proposed.

Different ratios of Canna indica and maize-vermicompost as biofertilizers to improve soil fertility and plant growth: A case study from southwest China.

Vermicomposting is recommended as an eco-friendly technology for an organic amendment to avoid the excessive use of inorganic fertilizers, which are causing environmental pollution. Here, this study evaluated soil fertility and plant growth after vermicompost amendment using reclaimed wetland plants and manure. A pot experiment was conducted to assess the seven treatments for nutrient recovery and plant growth: a control group without any fertilization (CK); four groups with vermicompost prepared from different ratios of ecological wetland plant residues, maize, and pig manure (V1, 4:6; V2, 5:5; V3, 6:6; and V4, 7:3); one group with only Canna indica (V5, Ci), and a group with synthetic fertilizers (NPK). The results showed the remarkable impacts of Ci-vermicompost and different ratios of organic fertilizer on soil fertility and plant height (28.8%) as major outcomes. In addition, vermicompost substantially increased soil total nitrogen (60.5%), soil organic matter (60.9%) including dissolved organic carbon (52.2%), and shoot biomass (V4, three-fold increase) compared with NPK and CK. Overall, the findings of this study suggest that vermicomposting combined with wetland plants is a feasible method for organic amendments and offers an innovative approach for recycling ecological waste to produce nutrient-rich organic fertilizers, reduce environmental damage, and improve crop production.

Soil enzyme activity and stoichiometry in secondary grasslands along a climatic gradient of subtropical China.

Soil extracellular enzymes plays key roles in ecosystem carbon (C), nitrogen (N), and phosphorus (P) cycling, and are very sensitive to climatic, plant, and edaphic factors. However, the interactive effects of these factors on soil enzyme activities at large spatial scales remain unclear. Here, we investigated the spatial pattern of the activities of five soil hydrolyzing enzymes [ß-D-cellobiohydrolase (CB), ß-1,4-glucosidase (BG), ß-1,4-N-acetyl-glucosaminidase (NAG), L-leucine aminopeptidase (LAP), and acid phosphatase (AP)], and their C:N:P acquisition ratios in relation to plant inputs and edaphic properties across a 600-km climatic gradient in secondary grasslands of subtropical China. The activities of CB, BG, and NAG decreased while that of LAP increased with the increasing mean annual temperature (MAT). The activities of all enzymes did not significantly vary with the mean annual precipitation (MAP). We found that the activities of BG, NAG, and AP were predominately dependent on plant N contents, while the soil LAP activity was tightly related to soil recalcitrant C and N contents. In contrast, the ecoenzymatic C:nutrient (N and P) acquisition ratios increased with increasing MAP and decreasing MAT, primarily due to the increase in plant input at warmer and wetter sites. In addition to climates, plant C inputs, C use efficiency, soil pH, soil organic C, soil C:P, and N:P ratios explained 79% and 72% of the overall variation in ecoenzymatic C:nutrient and P:N acquisition ratios, respectively. The pattern of ecoenzymatic C:N:P acquisition ratios also revealed unexpected N limitation in subtropical grasslands. Overall, our study highlighted the importance of climate in controlling soil biological C, N, and P acquisition activities through its direct and indirect effects on plant inputs and soil edaphic factors, thereby providing useful information for better understanding and predictions of soil C and nutrient cycling in grassland ecosystems at regional scales.

Soil nitrogen dynamics at a regional scale along a precipitation gradient in secondary grassland of China.

The availability of soil inorganic nitrogen (N) is primarily regulated by the rates of soil N transformation, including mineralization, ammonification, nitrification, and denitrification, and are sensitive to climate, plant, and soil factors. However, the interactive effects among these factors regulating soil N transformation rates in ecosystems across large spatial scales remain unclear. Here, we investigated the spatial patterns of the potential N mineralization, nitrification, ammonification, and denitrification rates in relation to plant traits and soil edaphic conditions across a 600-km precipitation gradient in secondary grasslands of South China. The soil potential N mineralization and nitrification rates significantly increased with increasing precipitation. However, the soil potential N ammonification and denitrification rates did not significantly vary with precipitation. Moreover, the soil potential N nitrification and denitrification rates significantly increased with increasing soil pH, whereas the potential N mineralization and ammonification rates decreased with increasing soil pH. The soil potential N mineralization rate was positively correlated with soil labile N but negatively correlated with soil recalcitrant C and N contents. Our results revealed that changes in soil NH4+-N and pH along precipitation gradients primarily controlled the potential N mineralization, nitrification, and ammonification rates. In contrast, soil NO3--N, soil pH, and plant N inputs predominantly regulated the potential N denitrification rate. Overall, our results reveal that soil N transformation varies along the precipitation gradient, and these results need to be considered when studying the effects of climate change on N cycling in grassland ecosystems across diverse environments.

Soil labile and recalcitrant carbon and nitrogen dynamics in relation to functional vegetation groups along precipitation gradients in secondary grasslands of South China.

Soil labile and recalcitrant carbon (C) and nitrogen (N) are strongly controlled by plant inputs and climatic conditions. However, the interrelation of labile and recalcitrant pools with changes in plant functional groups (i.e., C3 and C4) along precipitation gradients is not fully understood. Here, we investigated the soil organic C and N (SOC and SON), labile C and N (LC and LN), recalcitrant C and N (RC and RN), and their isotopes (δ13C, and δ15N) in relation to C3 and C4 plant inputs from 20 sites across a 600-km precipitation gradient in secondary grasslands of South China. The SOC content decreased first slightly and then increased along precipitation gradients, largely due to the increase in C4 plant C inputs in the lower precipitation regions. In contrast, the SON content increased with increasing N inputs from C3 plant at higher precipitation regions. The LC and LN contents increased with increasing precipitation, whereas RC and RN did not change with precipitation. The LC and LN were correlated with plant C and N contents, as well as the mean annual precipitation, respectively. Increases in LC and LN stocks were tightly related to enhanced plant C and N inputs influenced by precipitation, suggesting stronger sensitivity of labile pools to both plant functional groups inputs and precipitation compared to the recalcitrant pool. Moreover, the δ13C values in RC declined with precipitation, while the δ15N values of both labile and recalcitrant N increased with increasing precipitation, further revealing that soil labile and recalcitrant C and N pools closely related to the shift in the C3 and C4 plant along precipitation gradients. Overall, our findings indicated that soil labile and recalcitrant fractions should be considered in context of precipitation under which plant inputs takes place in predicting soil C and N dynamics.