Abatement of Nitrate Pollution in Groundwater and Surface Runoff from Cropland Using Legume Cover Crops with No-Till Corn

Agricultural practices can have a significant impact on water quality. The effects of leguminous winter cover crops on leaching of NO-3; from soil have been investigated in this project. Legume cover crops, by fixation of atmospheric N, can reduce the amount of fertilizer N required to produce summer grain crops. The methods initially used to evaluate cover crop effects on No; transport included suction probe lysimeters and measurement of NO-3; in soil samples collected to a depth of 90 cm. These measurements demonstrated extreme spatial variability in NO-3; distribution and water movement. This made it impractical to compare effects of different treatments. Soil transformations of legume and fertilizer N sources were compared using 15N labelled amendments. Less of the vetch N was found in leachable forms and, after 2 to 3 months in soil, losses of vetch N were smaller than losses of fertilizer N. To resolve the problem of spatial variability and to make direct measurements of leaching, 16 lysimeters were constructed from 55 gallon drums. These were treated with either fertilizer or legume N. Early measurements show greater NO-3; leaching with legume N, due to the mulch effect reducing evaporative water removal. However, there has been insufficient time to fully evaluate the treatments. This experiment will be continued

Determinantes de la generación de Residuos Sólidos Urbanos: El caso de los municipios de la provincia de Buenos Aires

Este trabajo tiene por objetivo estudiar los determinantes de la generación de residuos sólidos urbanos (RSU) y testear la hipótesis de la curva de Kuznets para el caso de la PBA. Se utiliza un corte transversal de la CABA y 125 municipios de la PBA. Dado que la generación de residuos es un problema con una dimensión espacial importante, se utiliza econometría espacial para considerar el posible efecto de la generación de residuos de un municipio sobre otros y se distinguen efectos directos, de indirectos y totales. Los resultados muestran una relación lineal entre la generación de RSU y el PBGpc del propio municipio. Al incorporar efectos espaciales, se observa que variaciones en el PBGpc de los municipios vecinos tienen un efecto no lineal en la generación de residuos del municipio en cuestión. La densidad poblacional tiene forma convexa y la relación entre la distancia desde el centro municipal hasta el basurero tiene forma de U invertida. Finalmente, se incorporaron tres variables dicotómicas: si el basural es a cielo abierto, si se clasifican o no los residuos y si el municipio es coordinado por CEAMSE. Las dos primeras no presentan un efecto significativo, pero la tercera sí y es negativo.Facultad de Ciencias Económica

Associative Nitrogen Fixation Linked With Three Perennial Bioenergy Grasses In Field and Greenhouse Experiments

© 2020 The Authors. Associative nitrogen (N2)‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive \u3e30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15N2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15N of soil, chicory, and sorghum, δ15N~+7.0). Isotopically labeled 15N2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15N2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil

Site-specific seeding using multi-sensor and data fusion techniques : a review

Site-specific seeding (SSS) is a precision agricultural (PA) practice aiming at optimizing seeding rate and depth, depending on the within field variability in soil fertility and yield potential. Unlike other site-specific applications, SSS was not adopted sufficiently by farmers due to some technological and practical challenges that need to be overcome. Success of site-specific application strongly depends on the accuracy of measurement of key parameters in the system, modeling and delineation of management zone maps, accurate recommendations and finally the right choice of variable rate (VR) technologies and their integrations. The current study reviews available principles and technologies for both map-based and senor-based SSS. It covers the background of crop and soil quality indicators (SQI), various soil and crop sensor technologies and recommendation approaches of map-based and sensor-based SSS applications. It also discusses the potential of socio-economic benefits of SSS against uniform seeding. The current review proposes prospective future technology synthesis for implementation of SSS in practice. A multi-sensor data fusion system, integrating proper sensor combinations, is suggested as an essential approach for putting SSS into practice