Raj K. Shrestha

Strategies to Reduce Nitrate Leaching into Groundwater in Potato Grown in Sandy Soils: Case Study from North Central USA

There is increasing public concern to reduce nitrate pollution to groundwater, especially in sandy soils. Strategies to reduce nitrate leaching are developed to increase N use efficiency, reduce groundwater pollution, and increase tuber yield. A growing interest in N management should consider management strategies for N supply, soil moisture for transport, and crop N demand that are economical and compatible with local production systems. We present a review of the literature on conventional and innovative strategies for N, irrigation, and crop management for potato production in reducing N leaching in sandy soils. The amount of fertilizer-N should be decided based on an integrated evaluation of soil organic matter content, soil texture, residual soil N, crop residues, credit to organic N sources, crops to be grown including varieties and crop physiological needs, cropping systems, yield potential, water management, and N concentrations in irrigation water. Research advances have no quick fix for controlling NO3 leaching to groundwater. However, the best combination of proven strategies can reduce leaching potential significantly.ResumenExiste una preocupación pública en aumento para reducir la contaminación de nitrato en el agua del subsuelo, especialmente en suelos arenosos. Se han desarrollado estrategias para reducir la lixiviación de nitratos para aumentar el uso eficiente de N, reducir la contaminación del agua del subsuelo, y para aumentar el rendimiento de tubérculo. Un interés en aumento en manejo de N debería de considerar estrategias de manejo para suministro de N, humedad del suelo para el transporte, y demanda de N del cultivo que sean económicas y compatibles con los sistemas locales de producción. Presentamos una revisión de la literatura en las estrategias convencionales e innovativas para el manejo de N, riego y del cultivo para producción de papa en la reducción de la lixiviación de N en suelos arenosos. La cantidad del fertilizante nitrogenado deberá decidirse con base a una evaluación integrada del contenido de materia orgánica en el suelo, textura, N residual, residuos de cosecha, reconocimiento a las fuentes de N orgánico, cultivos a sembrarse incluyendo variedades y necesidades fisiológicas del cultivo, sistemas de cultivo, potencial de rendimiento, manejo del agua, y concentraciones de N en el agua de riego. Los avances en investigación no tienen un remedio rápido para controlar la lixiviación de NO3 al agua del subsuelo. No obstante, la mejor combinación de estrategias probadas pueden reducir significativamente el potencial de lixiviación.

Greenhouse Gas Emissions and Global Warming Potential of Reclaimed Forest and Grassland Soils

Although greenhouse gas (GHG) emissions from soils are important, reclaimed mine soil (RMS) ecosystems are not widely assessed. Postreclamation land uses (forest, hay, and pasture) were investigated to: (i) monitor the magnitude of GHG fluxes, (ii) estimate their global warming potential (GWP), (iii) identify the relationship between GHG fluxes and soil properties, and (iv) develop a soil quality index by principal component analysis (PCA). The GHG fluxes were measured for 1 yr cycle and simultaneous measurements were also made for soil moisture and temperature. The RMS-forest, -hay, and -pasture land uses had weighted average fluxes of 1.16, 1.66, and 3.06 g CO(2)-C m(-2) d(-1); 0.33, 0.48 and 1.1 mg CH(4)-C m(-2) d(-1); and 0.33, 0.70, and 1.06 mg N(2)O-N m(-2) d(-1), respectively. The CO(2), CH(4), and N(2)O fluxes were consistently high in the RMS-pasture and low in the RMS-forest. The GWP (CO(2)-C equivalent) of the postreclamation land uses was in the order of RMS-forest (4.5 Mg ha(-1) yr(-1)) = RMS-hay (6.8 Mg ha(-1) yr(-1)) < RMS-pasture (12.3 Mg ha(-1) yr(-1)). The PCA showed that four PCs with eigenvalues > 1 explained 88.8% of the total variance in the soil properties. The first PC is mostly characterized by soil physical properties and the second by chemical properties. Soil and air temperatures were positively correlated with CO(2), CH(4), and N(2)O fluxes. The results suggest that GWP from RMS can be minimized by establishing forest land use.