Sampson Agyin-Birikorang

Characterization of Adsorption and Degradation of Diuron in Carbonatic and Noncarbonatic Soils

The adsorption and degradation of the pesticide diuron in carbonatic and noncarbonatic soils were investigated to better understand the fate and transport of diuron in the environment. Batch adsorption experiments yielded isotherms that were well-described by the linear model. Adsorption coefficients normalized to soil organic carbon content (K(oc)) were lowest for carbonatic soils, averaging 259 +/- 48 (95% CI), 558 +/- 109, 973 +/- 156, and 2090 +/- 1054 for carbonatic soils, Histosols, Oxisols, and Spodosols, respectively. In addition, marl-carbonatic soils had much lower K(oc) values (197 +/- 27) than nonmarl-carbonatic soils. Diuron degradation data fit a first-order reaction kinetics model, yielding half-lives in soils ranging from 40 to 267 days. There was no significant difference between the average diuron degradation rate coefficients of each of the soil groups studied. Given the low adsorption capacity of carbonatic soils, it may be advisable to lower herbicide application rates in agricultural regions with carbonatic soils such as southern Florida to protect aquatic ecosystems and water quality.

SUSTAINABLE NUTRIENT MANAGEMENT PACKAGE FOR COST-EFFECTIVE BIOENERGY BIOMASS PRODUCTION

Commercial fertilizer (particularly nitrogen) costs account for a substantial portion of the total production costs of cellulosic biomass and can be a major obstacle to biofuel production. In a series of greenhouse studies, we evaluated the feasibility of co-applying Gibberellins (GA) and reduced nitrogen (N) rates to produce a bioenergy crop less expensively. In a preliminary study, we determined the minimum combined application rates of GA and N required for efficient biomass (sweet sorghum, Sorghum bicolor) production. Co-application of 75 kg ha−1 (one-half of the recommended N rate for sorghum) and a modest GA rate of 3 g ha−1 optimized dry matter yield (DMY) and N and phosphorus (P) uptake efficiencies, resulting in a reduction of N and P leaching. Organic nutrient sources such as manures and biosolids can be substituted for commercial N fertilizers (and incidentally supply P) to further reduce the cost of nutrient supply for biomass production. Based on the results of the preliminary study, we conducted a second greenhouse study using sweet sorghum as a test bioenergy crop. We co-applied organic sources of N (manure and biosolids) at 75 and 150 kg PAN ha−1 (representing 50 and 100% N rate respectively) with 3 g GA ha−1. In each batch of experiment, the crop was grown for 8 wk on Immokalee fine sand of minimal native fertility. After harvest, sufficient water was applied to soil in each pot to yield ∼1.5 L (∼0.75 pore volume) of leachate, and analyzed for total N and soluble reactive P (SRP). The reduced (50%) N application rate, together with GA, optimized biomass production. Application of GA at 3 g ha−1, and the organic sources of N at 50% of the recommended N rate, decreased nutrient cost of producing the bioenergy biomass by ∼

Nitrogen uptake kinetics of key staple cereal crops in different agro-ecological regions of the world

375 ha−1 (>90% of total nutrient cost), and could reduce offsite N and P losses from vulnerable soils.

Changes of Soil Microbial Population and Structure Under Short-term Application of an Organically Enhanced Nitrogen Fertilizer

ABSTRACT The study was undertaken to assess the effect of environmental, management, and stress factors on nitrogen uptake patterns through the crops’ growth cycle and to associate temporal patterns of N uptake with biomass and grain yields. Existing complete experimental data, provided by several institutional databases and through an extensive literature review, were utilized together with crop simulation models (CSMs) to synthesize yield and N uptake profiles of the key staple cereal crops in selected agro-ecologies. Approximately 465 observations were identified for combined maize grain yield and plant N uptake: 156 for rice and 254 for wheat. The Decision Support System for Agrotechnology Transfer (DSSAT), which comprises CSMs and data that integrate capabilities on soils, daily weather, crops, and management, was used in combination with field information to first validate the CERES-maize, -rice, and -wheat models. The most noteworthy results from synthesis of the data set for the three key cereals were as follows: (a) N uptake continued to increase with time until physiological maturity with adequate N supply; (b) significant effect of soil N status on N uptake kinetics was observed at zero N; (c) N uptake profile was also influenced by the planting date, with the summer planting showing higher uptake than other planting dates; (d) field methods of N application influenced N uptake kinetics: a one-time injected or subsurface-applied urea continued to provide an adequate amount of N throughout the crop growth phase that was comparable or even higher than with broadcasting multiple splits; (e) N uptake was also dependent on crop cultivars, including stages of vegetative and reproductive phases, with shorter vegetative and longer reproductive phases showing continuous N uptake and lesser dependence on N remobilization; and (f) predictions suggested that modest changes in ambient temperature and atmospheric carbon dioxide (CO2) concentrations would not significantly alter the N uptake kinetics, with the uptake rate expected to increase under future climate change scenarios. The combined data suggest that no one N uptake kinetic pattern fits all crops under all environments and management practices.

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

Abstract Interest in the use of alternate fertilizers has increased during recent years to improve soil productivity. An organically enhanced N fertilizer, containing 14.9% N, 4.3% P2O5, 18.1% S, 0.6% Fe, and 8% organic C, and is produced from a sterilized organic additive extracted from municipal wastewater biosolids and chemical fertilizers was evaluated for its effects on soil microbial populations and abundances in 0- to 15-cm depth of of two silt loam soils located at Jackson and Grand Junction, Tennessee. This treatment was compared to conventional N fertilizers and zero N control under nonirrigated corn (Zea mays L.) from 2011 to 2013. Three N-applied treatments (organically enhanced N fertilizer, ammonium sulfate, urea/NPKZn briquette) at 128/170 kg ha−1 and the zero N control were imposed at each location. The organically enhanced N fertilizer decreased the relative abundance of arbuscular mycorrhizal fungi but increased that of general microbes relative to the zero N control and increased that of general microbes compared with NPKZn briquette 4 to 7 months after their applications at an N rate of 128 kg ha−1 for corn within 2 years of experimentation on a relatively infertile soil with low organic matter. Soil general microbes and arbuscular mycorrhizal fungi were the two sensitive indicators of soil microbial structure response to fertilization. However, effects of the organically enhanced N fertilizer on soil microbial populations were not noticeable after corn harvest. In conclusion, application of the organically enhanced N fertilizer has noticeable influence on soil microbial structure/abundance but not on populations on relatively infertile soils with low organic matter from a short-term perspective.

Composite micronutrient nanoparticles and salts decrease drought stress in soybean

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)’’.