Augustine K. Obour

USING TISSUE ANALYSIS AS A TOOL TO PREDICT BAHIAGRASS PHOSPHORUS FERTILIZATION REQUIREMENT

Tissue analysis in combination with soil testing has been recently incorporated in the fertilization recommendations for bahiagrass in Florida; however, limited research is available to validate the proposed critical tissue phosphorus (P) level. A greenhouse experiment was conducted to identify the critical minimum tissue P concentration below which bahiagrass dry matter (DM) yield is impacted. Treatments consisted of three nitrogen (N) rates (0, 50, and 100 kg N ha−1), four P rates (0, 20, 40, 60 kg P2O5 ha−1) and two clipping intervals (28 and 56 d). Bahiagrass yields and tissue P increased in response to P application. Phosphorus uptake showed a quadratic response to P rates when N was applied. Phosphorus recovery increased linearly as P rate increased. Root mass responded to P, even at the smallest (20 kg ha−1) rate. Data indicated that tissue P concentration of 1.3 (±0.2) g kg−1 can be used as an indicator of bahiagrass P deficiency.

The cow-calf industry and water quality in South Florida, USA: a review

Animal agriculture is often suggested as an important cause of water quality problems. This paper evaluates existing literature on the potential impacts of cow-calf production systems on water quality in South Florida, and provides a critical overview of the major gaps and limitations in the literature and present suggestions for future directions. Discrepancies in the literature suggest that there is a high degree of uncertainty associated with early estimates of the relative contribution of cow-calf operations to water quality problems in south Florida. Despite the extensive body of literature on this subject, limited information is available on the sources of P to the watershed and the relationship between land use, transport potential, water management, and climatic conditions controlling P loading. In addition, the relationships between urbanization, changes in land use, and potential impacts on water quality are important issues that have received little attention. Efforts should be placed on generating sound, science-based information about the real contribution of grazinglands to water quality issues. Maintaining and enhancing grazinglands and the natural resources associated with cow-calf ranches is essential to preserve Florida’s unique ecosystems.

Long-term residual effects of feedlot manure application on crop yield and soil surface chemistry

ABSTRACT Crop response to manure application may extend beyond the year of application due to residual nutrient availability. A field experiment was conducted to evaluate feedlot manure application (at 0 22.5, 45, 90 and 180 Mg ha−1) and subsequent residual effects (24-yr) on wheat and sorghum grain yields. Sorghum grain yields increased significantly with manure and nitrogen (N) fertilizer application. However, winter wheat grain yield showed no consistent response to manure and fertilizer application in the 9-yr when manure was applied. Averaged across the subsequent 24 years, residual feedlot manure and annual N fertilizer application significantly increased sorghum and winter wheat grain production. Application of cattle manure did increase soil organic matter content, pH and plant available soil nutrients. Our finding showed that growers could take advantage of the long-term benefits of nutrients supplied from manure application to bolster crop production, improve soil quality and reduce fertilizer input cost.

Wheat and Grain Sorghum Yields as Influenced by Long - term Tillage and Nitrogen Fertilizer Application

Tillage, choice of crops in a rotation, and fertilizer management affect crop yields. Limited information exist on long - term interaction effects of tillage and nitrogen (N) fertilizer management on grain yie ld and precipitation use efficiency (PUE) in intensified cereal - based cropping systems. A study was initiated at the Kansas State University Agricultural Research Center - Hays in 1975 to investigate the effect of tillage intensity [conventional tillage (CT ), reduced tillage (RT) and No - till (NT)] and N fertilizer rates (0, 22, 45 and 67 kg N ha - 1 ) on wheat and grain sorghum yields. Grain yields and PUE for both wheat and grain sorghum were significantly ( P 67 kg N ha - 1 ) may be required to maximize both wheat and grain sorghum yields with any of the tillage systems. Original Research Article

Soil Nutrients Status after Fifty Years of Tillage and Nitrogen Fertilization

ABSTRACT Long-term studies are valuable in assessing the impact of crop management practices on soil sustainability and function. This study used two calculation scenarios, fixed depth and Equivalent Soil Mass (ESM) to assess (i) soil nutrient status and (ii) soil organic carbon (SOC) after 50 years of nitrogen (N) fertilizer application rates (0, 22, 45, and 67 kg N ha−1) and tillage [clean tillage (CT), reduced tillage (RT), and no-tillage (NT)] in a dryland winter wheat-sorghum-fallow cropping system. The soil organic matter (SOM) content increased by 33% with NT and RT compared with CT. The SOC at 0–30 cm was 39% greater than 30–60 cm depth with both fixed depth and ESM calculations. Soil nutrient specifically soil calcium (Ca), magnesium (Mg), and phosphorus (P) associated with N rates were no different than the control. Crop nutrient removal may eventually reduce soil nutrient contents with only N application. Nutrient addition specifically P should be considered in the future.

Erratum to: Agro-ecological nitrogen management in soils vulnerable to nitrate leaching: a case study in the Lower Suwannee Watershed

In the original publication of the article, some sections were cited liberally from the previously published work. Authors regret for this error and would like to include the following sentence under the ‘‘Statistical Analysis’’ in the ‘‘Materials and Methods’’ section: ‘‘Analyses of the yield response model and economically optimum fertilizer rates, were carried out following the procedure described by Valkama et al. (2011)’’.