Landscapes typically deemed at risk from leached losses of nitrogen (N) and phosphorus (P) are those with short subsurface hydrologic time lags. Due to the short time it takes nutrients to move from a source to an area of concern, such sites are deemed perfect to test the efficacy of programmes of measures as management changes. However, a small subset of these sites can retain nutrients in soil/subsoil layers, which in turn are leached and can be either attenuated (e.g. nitrate converted to gaseous forms or immobilised in soil and P can be mineralised) or mobilised over time. This biogeochemical time lag can have long lasting effects on water quality. In an intensive agricultural karst oxidised aquifer setting, the aim of this study was to improve understanding of P and N inputs, retention, attenuation and subsurface pathway distribution and to inform how similar sites can be managed in the future. This was undertaken for the present site by integrating existing secondary and new primary datasets for both N and P. Results showed that in the years pre-2000 slurry from an on-site integrated pig production unit had been applied at rates of 33 t ha-1 annually, which supplied approximately 136 kg ha-1 total N and approximately 26 kg ha-1 total P annually. This practice contributed to large quantities of N (Total N and NH 4-N) and elevated soil test P (Morgan extractable P), present to a depth of 1 m. This store was augmented by recent surpluses of 263 kg N ha-1 , with leached N to groundwater of 82.5 kg N ha-1 with only 2.5 kg N ha-1 denitrified in the aquifer thereafter. High resolution spring data showed greatest percentage loss in terms of N load from small (54-88%) and medium fissure pathways (7-21%) with longer hydrologic time lags, with smallest loads from either large fissure (1-13%) or conduit (1-10%) pathways with short hydrologic time lags (reaction time at the spring from onset of a rainfall event is within hours). Although soils were saturated in P and in mobile forms to 0.5 m, dissolved reactive P concentrations in groundwater remained low due to Ca and Mg limestone chemistry. Depletion of the legacy store with no further inputs (taking 25% of available mass of soil organic N as available in 1 m of soil/subsoil to be 75 kg N ha-1) would take approximately 50 years, with NO 3-N concentrations in the source area dropping to levels that could sustain groundwater NO 3-N concentrations below admissible levels within 9 years. Biogeochemical time lags (decades) are longer than hydrologic time lags on this site (months to years). Future management should target farm surpluses that maintain a legacy store at or below a soil organic N mass of ~ 20 kg N ha-1. Incorporation of biogeochemical and hydrologic time lag principles into future water quality regulations will provide regulators with realistic expectations when implementing policies.

Manganese (Mn) as an essential plant micronutrient affects plant development, when at deficient or toxic levels. Manganese is used in several biological processes as an important contributor in plant growth and development. Manganese uptake depends on forms of Mn in soil solution, crop characteristics including growth rate, and ineteractions with other environmental factors. Its distribution in soils and requirement for crops vary from location to location, depending on soil type and reactions. Despite the metabolic roles of Mn in different plant cell compartments, the importance of Mn requirement in plants, distribution in soils and application to crops has been understated. As a micronutrient, judicious Mn management requires to critically evaluating its concentration in soils, biochemical functions, critical levels, soil availability and interactions with other nutrient elements is essential. This review has critically analysed the existing body of knowledge on Mn distribution in soils, dynamics, functions and management towards better crop production and safe environment. Environ. Sci. & Natural Resources, 12(1&2): 225-242, 2019

Development was conventionally driven by one particular need, without fully considering the wider or future impacts. This kind of approach has now been considered to be responsible for the economic and environmental catastrophes that humans are facing: from large scale financial crises caused by irresponsible banking to the changes in global climate resulting from our dependence on fossil fuel based energy sources. Soils provide essential ecosystem services such as primary production, regulation of biogeochemical cycles (with consequences for the climate), water filtration, resistance to diseases and pests, and regulation of above-ground biodiversity. Changing of the climate systems is unequivocal. Adaptation to global climate change through improved soil quality by adoption of improved management practices is key to maintaining sustainable agricultural production. A holistic approach to soil management as the engine for increasing productivity by increasing resource use efficiency and making agriculture environmentally compatible is more important than ever before. Strategies of greenhouse gas emission reduction include those that increase the use efficiency of inputs. Herein, we discussed how management and protection of soil resources can contribute to sustainable development through sustainable agricultural production while maintaining sustenance of soil fertility. J. Environ. Sci. & Natural Resources, 11(1-2): 159-170 2018

Soil physico-chemical properties are an important phenomenon for sustainable crop production and maintenance of optimum soil health. Hence, a laboratory measurement was conducted with soil samples of three years long experimental field of the Department of Soil Science, Bangladesh Agricultural University, Mymensingh to assess the changes in five selected soil physico-chemical properties viz. soil texture, bulk density, soil pH, total nitrogen and organic matter. The experiment was laid out in a split plot design with two water regimes (continuous flooding and alternate wetting & drying) in the main plots and five fertilizer treatments (N0 - control, N1- 140 kg N/ha as PU, N2- 104 kg N/ha as USG (2× 1.8 g/ 4 hills), N3 - 5 t CD + PU @ 140 kg N /ha on IPNS basis and N4- 5 t CD + USG (2× 1.8 g/ 4 hills @ 104 kg N/ha)) in the subplots under rice-rice cropping pattern with three replications. After three years, soil samples were collected at 0-5 and 5-10 cm soil depths for measuring bulk density and at 0-10 cm depth for other soil properties and analyzed. Results found that % sand, % silt, % clay, bulk density and soil pH was not changed significantly compared to initial status. Percentage of total nitrogen and organic matter was significantly affected by irrigation and fertilization. Total nitrogen (%) was higher in AWD whereas organic matter (%) was higher in CF practice. The highest total nitrogen (%) and organic matter (%) was found in N4 treatment in which USG was applied in combination with cowdung as organic manure. It can be suggested that N4 treatment was formed good combination for sustaining chemical properties of soil. Further long- term experimentation will be needed to know the changes in soil properties for sustainable crop production and improving soil health. Asian Australas. J. Biosci. Biotechnol. 2020, 5 (2), 65-71

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