Evaluation of Fertilizer Additives for Enhanced Nitrogen Efficiency in Corn

The use of N additives and slow release materials with ammoniacal fertilizer varies throughout the U.S. Corn Belt due to differing N loss potentials across climate, soils, and production systems. In Iowa, recent years of high rainfall events and prolonged wet soil conditions has renewed interest to protect fertilizer N loss from denitrification, leaching, and greenhouse gas emission with use of nitrification inhibitors. These loss processes can be significant in Iowa soils that are poorly drained and have high organic matter, high pH, and high populations of denitrifying bacteria. Subsurface tile drainage is also prevalent in farmer fields throughout the state, a contributing pathway for nitrate leaching. Leaching loss is the major contributor to N in surfaces waters reaching the Gulf of Mexico. Farmers who utilize minimum or no-tillage systems can benefit from urease inhibitors to minimize volatilization from surface applied urea or urea containing fertilizers. Evaluation of urease and nitrification inhibitors, and slow release fertilizer products, is needed to best provide advice to farmers on appropriate use with urea fertilizers for agronomic performance, as well as potential to aid in reducing loss that affects water and air quality. Urea is an important N fertilizer source across the Corn Belt, with consumption in Iowa at approximately 180,500 U.S. tons (2010-2011 fertilizer year). Proper and improved use efficiency options are important for farmers. The objective of the study was to determine the effect of urease inhibitors, nitrification inhibitors, and slow release urea products on soil inorganic-N, N use efficiency and yield in corn biomass and grain, and nitrous oxide (N2O) emission from soil

Supervised learning using a symmetric bilinear form for record linkage

Record Linkage is used to link records of two different files corresponding to the same individuals. These algorithms are used for database integration. In data privacy, these algorithms are used to evaluate the disclosure risk of a protected data set by linking records that belong to the same individual. The degree of success when linking the original (unprotected data) with the protected data gives an estimation of the disclosure risk. In this paper we propose a new parameterized aggregation operator and a supervised learning method for disclosure risk assessment. The parameterized operator is a symmetric bilinear form and the supervised learning method is formalized as an optimization problem. The target of the optimization problem is to find the values of the aggregation parameters that maximize the number of re-identification (or correct links). We evaluate and compare our proposal with other non-parametrized variations of record linkage, such as those using the Mahalanobis distance and the Euclidean distance (one of the most used approaches for this purpose). Additionally, we also compare it with other previously presented parameterized aggregation operators for record linkage such as the weighted mean and the Choquet integral. From these comparisons we show how the proposed aggregation operator is able to overcome or at least achieve similar results than the other parameterized operators. We also study which are the necessary optimization problem conditions to consider the described aggregation functions as metric functions

Nitrogen, carbon, and phosphorus balances in Iowa cropping systems: Sustaining the soil resource

The Corn Belt’s exceptional productivity depends on high soil organic carbon and nutrient stocks (that is, the amount of carbon and nutrients stored in the soil). However, there is growing concern among scientists and farmers that soil carbon, nitrogen, and phosphorus stocks in corn-based cropping systems may be declining as a result of outputs that exceed inputs. The lack of certainty about the status of soil carbon and nutrient stocks is largely due to the extreme difficulty associated with measurement of inputs, outputs, and stocks of soil organic carbon and nutrients

Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept

Labile, ‘high-quality’, plant litters are hypothesized to promote soil organic matter (SOM) stabilization in mineral soil fractions that are physicochemically protected from rapid mineralization. However, the effect of litter quality on SOM stabilization is inconsistent. High-quality litters, characterized by high N concentrations, low C/N ratios, and low phenol/lignin concentrations, are not consistently stabilized in SOM with greater efficiency than ‘low-quality’ litters characterized by low N concentrations, high C/N ratios, and high phenol/lignin concentrations. Here, we attempt to resolve these inconsistent results by developing a new conceptual model that links litter quality to the soil C saturation concept. Our model builds on the Microbial Efficiency-Matrix Stabilization framework (Cotrufo et al., 2013) by suggesting the effect of litter quality on SOM stabilization is modulated by the extent of soil C saturation such that high-quality litters are not always stabilized in SOM with greater efficiency than low-quality litters

Does Nitrogen Fertilizer Application Rate to Corn Affect Nitrous Oxide Emissions from the Rotated Soybean Crop?

Little information exists on the potential for N fertilizer application to corn (Zea mays L.) to affect N2O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N2O emissions during subsequent crops in rotation, we measured N2O emissions for 3 yr (2011–2013) in an Iowa, corn–soybean [Glycine max (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha−1, the recommended rate of 135 kg N ha−1, and a high rate of 225 kg N ha−1); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye (Secale cereale L.) cover crop to interact with N fertilizer rate to affect N2O emissions from both crops. The cover crop did not consistently affect N2O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N2O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0–225 kg N ha−1) did not affect mean N2O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N2O flux rates from the soybean crops that received 135 and 225 kg N ha−1 N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N2O emissions are not easily generalizable. When N fertilizer affects N2O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N2O emissions are altered or only spread across a greater period of time

Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized

Nitrogen fertilization is critical to optimize short-term crop yield, but its long-term effect on soil organic C (SOC) is uncertain. Here, we clarify the impact of N fertilization on SOC in typical maize-based (Zea mays L.) Midwest U.S. cropping systems by accounting for site-to-site variability in maize yield response to N fertilization. Within continuous maize and maize-soybean [Glycine max (L.) Merr.] systems at four Iowa locations, we evaluated changes in surface SOC over 14 to 16 years across a range of N fertilizer rates empirically determined to be insufficient, optimum, or excessive for maximum maize yield. Soil organic C balances were negative where no N was applied but neutral (maize-soybean) or positive (continuous maize) at the agronomic optimum N rate (AONR). For continuous maize, the rate of SOC storage increased with increasing N rate, reaching a maximum at the AONR and decreasing above the AONR. Greater SOC storage in the optimally fertilized continuous maize system than in the optimally fertilized maize-soybean system was attributed to greater crop residue production and greater SOC storage efficiency in the continuous maize system. Mean annual crop residue production at the AONR was 22% greater in the continuous maize system than in the maize-soybean system and the rate of SOC storage per unit residue C input was 58% greater in the monocrop system. Our results demonstrate that agronomic optimum N fertilization is critical to maintain or increase SOC of Midwest U.S. cropland

La participación de los beneficiarios en el ciclo de los proyectos de desarrollo.

Los proyectos de desarrollo constituyen un tipo especial de proyectos, ya que son entes cambiantes que pueden variar de acuerdo a la necesidad de cumplir con los objetivos planteados (Hernandez, Negrillo, Sagua, and Yague, 2011). Estos cambios, debido a la interacción con personas y su entorno, deben observarse a la hora de desarrollar estos proyectos, dándoles cierta flexibilidad tanto en la planificación como en la ejecución y permitiendo que la participación de los beneficiarios pueda aportar conocimiento local y la co-ejecución con los beneficiarios. La presente comunicación plantea una modificación al diagrama clásico de los proyectos de desarrollo, incluyendo la retroalimentación en todas sus etapas debido a la participación de los beneficiarios, a través de la aplicación del aprendizaje social como modelo de planificación y ejecución de proyectos de desarrollo, lo que enriquece el proceso de manera continua. La comunicación presentada es parte de la investigación sobre la consecución de una metodología que permita la ejecución de aquellos tipos de proyectos de desarrollo que por su complejidad no puedan ser abordados por la teoría clásica de proyectos