A review on effective soil health bio-indicators for ecosystem restoration and sustainability.

Preventing degradation, facilitating restoration, and maintaining soil health is fundamental for achieving ecosystem stability and resilience. A healthy soil ecosystem is supported by favorable components in the soil that promote biological productivity and provide ecosystem services. Bio-indicators of soil health are measurable properties that define the biotic components in soil and could potentially be used as a metric in determining soil functionality over a wide range of ecological conditions. However, it has been a challenge to determine effective bio-indicators of soil health due to its temporal and spatial resolutions at ecosystem levels. The objective of this review is to compile a set of effective bio-indicators for developing a better understanding of ecosystem restoration capabilities. It addresses a set of potential bio-indicators including microbial biomass, respiration, enzymatic activity, molecular gene markers, microbial metabolic substances, and microbial community analysis that have been responsive to a wide range of ecosystem functions in agricultural soils, mine deposited soil, heavy metal contaminated soil, desert soil, radioactive polluted soil, pesticide polluted soil, and wetland soils. The importance of ecosystem restoration in the United Nations Sustainable Development Goals was also discussed. This review identifies key management strategies that can help in ecosystem restoration and maintain ecosystem stability.

Acid drainage from coal mining: Effect on paddy soil and productivity of rice.

Overburden and acid drainage from coal mining is transforming productive agricultural lands to unproductive wasteland in some parts of Northeast India. We have investigated the adverse effects of acid mine drainage on the soil of rice paddy and productivity by comparing them with non-mined land and abandoned paddy fields of Jaintia Hills in Northeast India. Pot experiments with a local rice cultivar (Myngoi) as test crop evaluated biological productivity of the contaminated soil. Contamination from overburden and acid mine drainage acidified the soil by 0.5 pH units, increased the exchangeable Al3+ content 2-fold and its saturation on clay complexes by 53%. Available sulfur and extractable heavy metals, namely Fe, Mn and Cu increased several-fold in excess of critical limits, while the availability of phosphorus, potassium and zinc contents diminished by 32-62%. The grain yield of rice was 62% less from fields contaminated with acid mine drainage than from fields that have not suffered. Similarly, the amounts of vegetation, i.e. shoots and roots, in pots filled with soil from fields that received acid mine drainage were 59-68% less than from uncontaminated land (average shoot weight: 7.9±2.12gpot-1; average root weight: 3.40±1.15gpot-1). Paddy fields recovered some of their productivity 4years after mining ceased. Step-wise multiple regression analysis affirmed that shoot weight in the pots and grain yield in field were significantly (p<0.01) and positively influenced by the soil's pH and its contents of K, N and Zn, while concentration of S in excess of threshold limits in contaminated soil significantly (p<0.01) reduced the weight of shoots in the pots and grain yield in the field.

Monitoring changes in soil organic carbon pools, nitrogen, phosphorus, and sulfur under different agricultural management practices in the tropics.

Soil organic matter not only affects sustainability of agricultural ecosystems, but also extremely important in maintaining overall quality of environment as soil contains a significant part of global carbon stock. Hence, we attempted to assess the influence of different tillage and nutrient management practices on various stabilized and active soil organic carbon pools, and their contribution to the extractable nitrogen phosphorus and sulfur. Our study confined to the assessment of impact of agricultural management practices on the soil organic carbon pools and extractable nutrients under three important cropping systems, viz. soybean-wheat, maize-wheat, and rice-wheat. Results indicated that there was marginal improvement in Walkley and Black content in soil under integrated and organic nutrient management treatments in soybean-wheat, maize-wheat, and rice-wheat after completion of four cropping cycles. Improvement in stabilized pools of soil organic carbon (SOC) was not proportional to the applied amount of organic manures. While, labile pools of SOC were increased with the increase in amount of added manures. Apparently, green manure (Sesbania) was more effective in enhancing the lability of SOC as compared to farmyard manure and crop residues. The KMnO(4)-oxidizable SOC proved to be more sensitive and consistent as an index of labile pool of SOC compared to microbial biomass carbon. Under different cropping sequences, labile fractions of soil organic carbon exerted consistent positive effect on the extractable nitrogen, phosphorus, and sulfur in soil.