Jorge A. Delgado

Drainage water management for water quality protection

L and drainage has been central to the development of North America since colonial times, with the first organized drainage efforts occurring as early as the 1600s (Evans et al. 1996). Drainage has been encouraged to improve public highways, reduce public health risks, promote increased crop yield and reduced yield variability, reduce surface runoff and erosion, and increase land value. Agricultural drainage includes artificial subsurface drainage and surface drainage. Most agricultural producers improve the drainage on their land for better trafficability, to enhance field conditions, to facilitate timely planting and harvesting operations, and to help decrease crop damage from saturated soil and standing water during the growing season. Agricultural drainage improvement also decreases year-to-year variability in crop yield, ensuring consistent production. Increasingly, agricultural drainage is being targeted as a conduit for pollution, particularly nutrient pollution (Needelman et al. 2007). Considerable resistance exists in some regions to the expansion of drainage systems despite their importance to food production, with up to 50% of the cropland in some states under artificial drainage. However, because drainage ditches and subsurface drainage systems convert diffuse flows from the landscape into concentrated flows, they also provide opportunities for precision conservation, the targeting of specific practices to…

Sap test to determine nitrate‐nitrogen concentrations in aboveground biomass of winter cover crops

Abstract In the San Luis Valley of south central Colorado, winter cover crops (WCC) are used to reduce soil erosion and scavenge residual soil‐N. Some San Luis Valley farmers are beginning to use WCC as a source of over‐winter or early‐spring grazing. Common WCC used by farmers, wheat (Triticum aestivum L.) and rye (Secale cereale L.) are reported to accumulate high levels of nitrate nitrogen (NO3 ‐‐N) in aboveground biomass that can be toxic to animals. Evaluation and calibration of a quick Cardy Meter2 Sap Test (CMST) for determination of NO3 ‐‐N status in the field will facilitate the management of these WCC. Field and growth chamber studies were conducted to correlate the CMST with laboratory procedures and with plant and soil parameters. In field and growth chamber studies, the CMST was correlated with standard dry tissue NC3 ‐‐N laboratory analysis (P<.001) and with soil inorganic N content (P<.05). These field and growth chamber studies show that the CMST can be a tool in helping farmers identify f...

Annual Precipitation and Effects of Runoff Nutrient From Agricultural Watersheds on Water Quality

Abstract Declining surface water quality from agricultural nonpoint sources is of great concern across the Great Plains. Trends in the earth climate create abrupt changes in domestic weather (i.e., precipitation) that can alter the impact of the nonpoint sources on water quality. A 2-year (dry 2009 and wet 2010) study was conducted to assess the impact of soil C, N, and S losses by runoff on water quality of Salt Creek in the Roca watershed, Nebraska. Average dissolved nutrient concentrations in runoff were 95.4 and 94.9% of the total for the dry and wet years, respectively. The remaining nutrients in runoff were associated with sediment. Nutrient concentrations during the dry year were generally greater than those during the wet year. Average concentrations for 2009 were 63.2, 1.87, and 53.5 mg/L for C, N, and S, respectively, whereas concentrations for 2010 were 54.0, 3.0, and 16.6 mg/L, respectively. Total soil nutrient losses were greater for the wet year than those for the dry year. The dry year nutrient losses were 607, 19,978, and 441,569 metric tons for C, N, and S, respectively, whereas losses for the wet year were 1,997, 138,380, and 608,172 metric tons, respectively. These losses could be considered as the annual nutrient loadings for Salt Creek. Concentrations of C, N, and S measured in Salt Creek during the study were not expected to have any adverse effect on human/animal health or aquatic life. We concluded that greater precipitation during the wet year increased the impact on water quality and soil fertility in the Roca watershed.

Opinion: Why we need a National Living Soil Repository

Soils are the keystone of healthy and vibrant ecosystems, providing physical, chemical, and biological substrates and functions necessary to support life. In particular, its the extensive and elaborate matrix of soil microorganisms and other life forms that contributes to soil health and utility.nnBut soils are under constant threat from heavy use, changing climate, and in some cases poor management (1, 2). In view of soil’s key role and threatened status, we believe that there is a need for the scientific community to undertake coordinated research and development efforts that will lead to a unique asset: a National Living Soil Repository (Fig. 1).nnnnFig. 1. nA National Living Soil Repository would store agricultural cryogenic and air-dried soil samples, analyze samples for microbial community composition, assess samples for microbial viability, and serve as a potential source of living organisms for various agricultural ecosystem services. Image courtesy of Jennifer Moore-Kucera (USDA Natural Resources Conservation Service) and Daniel Manter (USDA Agricultural Research Service).nnnnAlready local and national soil archives have been shown to be of great utility for studying, analyzing, and documenting long-term environmental and ecological trends. For example, the historical soil archive at Hubbard Brook helped researchers discover the link between fossil fuels and acidification of rain and snow (3); the Rothamsted Sample Archive in the United Kingdom has shown a steady increase in dioxins during the last century (4). And yet, a soil repository/archive designed to preserve native biological diversity does not currently exist.nnSuch an archive would provide the ability to acquire data on the current biological (e.g., soil health) state of soils around the country across soil types, cropping systems, and ecosystems and over time. Further, by maintaining soil archives and a catalog of their microbial communities, we will gain a better understanding of how soil organisms are distributed … nn[↵][1]1To whom correspondence should be addressed. Email: Jorge.Delgado{at}ars.usda.gov.nn [1]: #xref-corresp-1-1

A new nitrogen index for assessment of nitrogen management of Andean mountain cropping systems of Ecuador

Abstract Corn (Zea mays L.) is important for food security in much of Ecuador. Small-scale farmers are using nitrogen (N) fertilizer without technical advice based on soil, crop, and climatologic data. The literature lacks studies where tools that can quickly assess management practices’ effects on N uptake, N use efficiency, and risk of N losses to the environment in high-altitude mountain systems are validated. We tested corn response to fertilizer application and the capability of the Nitrogen Index to assess N dynamics within a conservation agriculture production system in a mountainous area of Ecuador. Responses to fertilizer were tested across six sites in the Bolivar province. Steep slopes and declining soil productivity make conservation agriculture a promising option in this area. However, N availability is limiting for corn production and better information is needed to optimize the system. Corn responded to fertilizer application with an average increase of 30 kg ha−1 corn grain per every 1 kg of N ha−1 applied (P < 0.001). The data suggest that N leaching increased with fertilizer application for areas with precipitation greater than 900 mm. The Nitrogen Index for Ecuador was able to quickly assess management practices’ effects on N uptake (P < 0.001), N use efficiency (P < 0.001), and risk of N losses. It could be used to increase use of best management practices in these systems.

Accumulation of Late-Applied Nitrogen and Root Dynamics during Grain Filling in Irrigated Spring Wheat

The objective of this study was to investigate the root growth and nitrogen (N) accumulation of spring wheat during grain filling under split N management. Two spring wheat genotypes were grown in a field with sandy loam soils at three levels of N fertilization (18, 21, and 24 g N m−2). Variations in N availability across soil depth were performed in additional experiments under controlled conditions in a greenhouse. The accumulations of total and late-applied N at maturity were 13% and 41% greater, respectively, for the genotype that had longer root length (+57%) and root-to-shoot ratio (+43%). The accumulation of 15N in the greenhouse study was 53% greater with 15N applied at a depth of 0.15 m than at a depth of 0.35 m. These results indicate that the genotype that accumulated more N was characterized by greater proliferation and maintenance of roots where N availability was greater.

15N uptake fom manure and fertilizer sources by three consecutive crops under controlled conditions

No mundo existem varias regioes em que as fontes de N e as analises de solo nao sao levadas em consideracao para determinar as necessidades desse elemento, o que resulta em aplicacoes excessivas, especialmente quando se utiliza esterco. Uma dessas regioes e a Centro-Norte do Mexico, chamada de La Comarca Lagunera, uma das maiores areas produtoras de leite do pais. Um experimento em casa de vegetacao foi realizado com fertilizante e esterco marcados com o isotopo N15 para monitorar a ciclagem e a recuperacao do N quando grandes quantidades sao aplicadas. O tratamento N15-esterco foi aplicado somente uma vez e incorporado no solo previamente a plantacao da primeira pastagem, com as seguintes doses: 30, 60 e 120 Mg ha-1 de materia seca. O tratamento N15-fertilizante consistiu na aplicacao de 120 e 240 kg (NH4)2SO4 ha-1 em cada cultivo. O total de N-fertilizante para cada tratamento foi de 360 e 720 kg ha-1 de N. A quantidade de N-esterco recuperado foi de 9 %, muito menor que a quantidade de N recuperado do fertilizante, que variou entre 22 e 25 %. A quantidade de N-esterco recuperado nas raizes e em profundidade no solo variou entre 82 e 88 %. A reduzida quantidade de N recuperado no solo nas formas de nitrato (NO3-N) e amonio (NH4-N) apos a terceira colheita indica que a maior parte do 15N recuperado estava na forma orgânica. As perdas de N-esterco variaram entre 3 e 11 %, sendo bem menores que as do N-fertilizante (34-39 %). Este estudo mostra que as aplicacoes excessivas de esterco e fertilizantes, rotineiramente empregadas na regiao, nao aumentam a taxa de absorcao de N pela biomassa aerea das culturas, mas incrementam as perdas de N no ambiente.