Cornstalk Testing to Evaluate Nitrogen Management

Recent studies have shown that the nitrogen (N) status of a corn crop can be assessed by measuring nitrate concentrations in the lower portion of cornstalks at the end of the growing season. This finding Jed to the development of a new tissue test that can be used to evaluate N management practices used in any field in any year. The test is called the end-of-season cornstalk test . This pamphlet describes the test and how it should be used

The End-of-Season Cornstalk Test for Excess Nitrogen

Recent studies have shown that the N status of a corn crop can be assessed by measuring nitrate concentrations in the lower portion of cornstalks at the end of the growing season. This finding lead to the development of a new tissue test that can be used to evaluate N management practices used in any field in any year. This evaluation gives feedback that can be used to improve N management. The test is called the end-of-season cornstalk test . It is a management tool that should be of interest to all corn producers and all who advise corn producers. The purpose of this paper is to describe the test and how it should be used

Soil quality, yield stability and economic attributes of alternative crop rotations

Three long-term rotational crop studies in Iowa and one in Wisconsin were examined for conclusive evidence of rotational effects on soil quality. Long-term yield data also were evaluated to determine if there was a quantifiable relationship between soil quality and yield or yield stability

Potassium Fertilization Guidelines in Iowa: Are They Working and Should Applications Be Adjusted with High Fertilizer Prices?

Iowa State University (ISU) researchers have conducted much research over time with help from Iowa farmers, crop consultants, and agribusiness to study potassium (K) fertilization of crops and use of soil-test K as a tool to determine crop K needs. Results of this research are reflected on current fertilizer recommendations, which are explained in the ISU Extension publications Pm-1688 and Pm-1310. The research continues to keep pace with changes of production practices, new hybrids and varieties, and new questions. This year Iowa farmers are looking very carefully at fertilization practices because recent sharp increases in fertilizer and fuel prices have not been matched by increases in grain prices. The ISU K recommendations were last updated for the 2003 crop year. The most significant changes were (1) to recommend maintenance of higher soil-test K levels for optimum crop production and (2) to suggest deep K fertilizer placement for grain crops managed with ridge-till and no-till systems. In this presentation we review the K recommendations and share highlights of recent on-farm research. Decisions about fertilization for any economic situation should be made based on knowledge of the probability and size of crop response to fertilization for different soil-test levels, fertilization rates, and prices

Potassium Fertilization Effects on Soil-Test Potassium and Yields of Corn and Soybeans

Iowa State University (ISU) interpretations for soil-test potassium (K) and fertilizer recommendations were updated in 2002. However, additional research is needed to confirm or continue improving the recommendations. The most significant change in the recommendations was to increase the soil-test K levels suggested for optimum crop production. The new interpretation classes (Very Low to Very High) and recommendations are explained in the ISU Extension publication Pm-1688, so details are not provided here. For example, the range of soil-test K values previously classified as Optimum (for which maintenance K fertilization is recommended) was 91 to 130 ppm (by the ammonium-acetate or Mehlich-3 K tests), but now this range is classified as Low and a higher K fertilization rate is recommended

Panamá: Una imagen país en construcción

Los países son cada vez más conscientes de la importancia de promover de forma positiva su imagen frente a los mercados internacionales. Algunas de las principales variables en las que un país está interesado fortalecer hacia el exterior pueden ser: atraer a los turistas, promover las exportaciones de las marcas nacionales, fomentar la inversión extranjera, entre otras. El turismo, hasta ahora, ha sido la variable más importante para las naciones que han desarrollado una marca país debido al dinamismo que genera en la economía local y en ello han centrado sus gestiones y esfuerzos. Sin embargo, según diversos autores citados en este estudio, una marca país con un enfoque holístico debe abordar y desarrollar las otras variables con la misma importancia.Introducción. Marco Teórico. Metodología. Percepción de los colombianos sobre Panamá. Campaña publicitaria marca país Panamá. Conclusiones. Bibliografía.Magister en Dirección de Marketing. CESA.Maestrí

Phosphorus indexing for cropland: Overview and basic concepts of the Iowa phosphorus index

Excessive phosphorus (P) loss from soils impairs surface water resources. An assessment tool or index has been proposed to identify fields with high potential risk of P delivery. The P index integrates P source and transport factors into a decision making process that may lead to changes in current P management and soil conservation practices. The index recognizes that a single soil P threshold alone is not an appropriate evaluation factor because of the varying conditions across fields. Although most indices being developed in the United States include similar factors, source and transport characteristics are considered in various ways to best address the variable conditions across regions. The Iowa P index reflects conditions that predominate under grain-crop production systems, considers source factors in a multiplicative manner within three main transport mechanisms, and approximates loads of P likely to enter and become available to aquatic ecosystems. An erosional component considers sheet and rill erosion, P enrichment, total soil P, buffers, sediment delivery, distance to a stream, and the long term biotic availability of particulate P in lake ecosystems. A runoff component considers water runoff based on a modification of the runoff curve number (RCN), soil-test P (STP), rate, time, and method of P application. An internal drainage component considers the presence of tiles, water flow to tile lines, subsurface recharge from subsurface flow, and soil-test P. When the erosion risk is high, the index weighs particulate P loss heavily compared with dissolved P loss, and emphasizes long-term processes comparatively more than short-term processes. This P assessment tool helps identify alternative P and soil conservation management options for reducing total P delivery from fields to surface water resources

Comparison of Dinitrogen Fixation and Nitrogen Transfer Potentials of Four Red Clover Cultivars

The capacity to fix atmospheric N2 and thus reduce the use of N fertilizer is an important reason for including legumes in forage mixtures. Selection for more efficient N2 fixation could improve red clover (Trifolium prateme L.) (RC) production and its contribution to soil fertility. An isotope dilution study was conducted in two greenhouse experiments to compare the N2 fixation and N transfer potentials of three commercial and one experimental RC cultivars. The experimental cultivar APR-8701 was selected for traits related to increased N2 fixation (rate of acetylene reduction, root size and branch number, and nodule mass). \u27Dawn\u27 orchardgrass (Dactylis glomerata L.) (OG) was used as the grass in mixture and as the reference crop for the isotope dilution study. Four harvests were taken from each of the two experiments. Herbage was analyzed first for total N and then for isotopic composition by mass spectrometry. Under the conditions of this study, the particular traits selected for in the development of the cultivar APR-8701 resulted in a high N2 fixation rate, ranging from 88.9 to 99.8 %N derived from the atmosphere (%Ndfa) in pure and mixed stands of both experiments, that paralleled the other three cultivars tested (ranging between 86.8 and 99. 9 %Ndfa in pure and mixed stands of both experiments). However, APR-8701 was average when N transfer potentials were compared. Average %N in grass derived from the atmosphere (%Ngdfa) was 32.2 and 46.3% for OG grown with APR-8701 in experiments 1 and 2, respectively, and ranged between 30. 5 and 50.1% for OG grown with the other three cultivars. We conclude that the experimental cultivar APR-8701 showed N2 fixation rates similar to that of other superior, commercially available cultivars, however, APR-8701 only showed average N transfer capability

The Cyprinodon variegatus genome reveals gene expression changes underlying differences in skull morphology among closely related species

Genes in durophage intersection set at 15 dpf. This is a comma separated table of the genes in the 15 dpf durophage intersection set. Given are edgeR results for each pairwise comparison. Columns indicating whether a gene is included in the intersection set at a threshold of 1.5 or 2 fold are provided. (CSV 13 kb

Supplemental Material for: Multi-site evaluation of APEX for water quality: II. Regional parameterization

Model performance was assessed using Nash-Sutcliffe model efficiency (NSE), coefficient of determination (r2), and percent bias (PBIAS) as defined by Moriasi et al. (2007 and 2015). Threshold values indicating acceptable model performance based on these statistics are dependent on the spatial and temporal scales of the data, water quality constituents of interest, and the modeling objectives (Moriasi et al., 2015). Although some standard values have been suggested (Moriasi et al., 2007 and 2015), considerable variability exist in the published literature. For instance Ramanarayan et al. (1997) considered r2 \u3e0.5 and NSE \u3e0.40 as satisfactory for simulation of monthly surface water quality with the APEX model. Chung et al. (2002) defined r2 \u3e 0.5 and NSE \u3e 0.3 as satisfactory for monthly tile flow and NO3-N loss simulated with the Erosion Productivity Impact Calculator (EPIC) model. Wang et al. (2008) indicated r2 \u3e 0.5 and NSE \u3e 0.4 as acceptable for monthly runoff and nutrient concentrations using the APEX model. Moriasi et al. (2007) suggested NSE \u3e 0.5 with P-bias ±25% for streamflow, ±55% for sediment and ±70% for nitrogen and phosphorus for monthly values. They also indicated that NSE values can be relaxed for shorter time steps (daily events). Yin et al. (2009) reported NSE for event based runoff and sediment between 0.41-0.84 and r2 between 0.55 - 0.85. Mudgal et al. (2010) regarded r2 \u3e 0.5 and NSE \u3e 0.45 as threshold for satisfactory calibration and validation with event data