Replacing Fertilizer with Dried Distillers' Grains in Stocker Cattle Systems on Southern Great Plains Old World Bluestem, USA.

The objective was to examine the effects of dried distillers' grains supplementation and fertilization strategies on the cattle performance and resource use efficiency of stocker cattle grazing on Plains Old World bluestem. Over 4 consecutive years, heifers and steers (average n = 239) were randomly assigned to 1 of 4 treatments: (1) low input, low stocking density, and no fertilizer or distillers grains supplementation (LOW); (2) high stocking density and no fertilizer with distillers grains supplementation (DDGS); (3) high stocking density and 90 kg of nitrogen/ha with no distillers grains supplementation (NFERT); (4) high stocking density, 90 kg of nitrogen/ha, and 39 kg of phosphorus/ha with no distillers grains supplementation (NPFERT). Cattle grazed in the pastures from mid-May to mid-September each year, except for 2011, when the experiment ended in July due to lack of forage. Data were analyzed using a linear model with fixed effects of treatment, year, and treatment × year (R software). Nitrogen use efficiency (retained/inputs) was affected by a treatment × year interaction, where LOW had the greatest efficiency in all years and DDGS was greater than NFERT and NPFERT in all years except 2012, with NFERT and NPFERT being not different in all years. The estimated total carbon equivalent emissions were greater for DDGS, NFERT, and NPFERT than LOW, but the carbon footprint (kg CO2eq/kg weight gain) was lesser for LOW and DDGS, which were not different, than NFERT and NPFERT, which were also not different. Replacing nitrogen fertilizer with dried distiller's grains improved the cattle performance and the efficiency of resource use, and could be a viable economic alternative to traditional systems.

Imazethapyr aqueous photolysis, reaction quantum yield, and hydroxyl radical rate constant.

The recent introduction of imidazolinone-tolerant rice varieties allow imazethapyr to be used in commercial rice. Little is known about imazethapyr photodegradation in the rice field. Laboratory studies were conducted to determine the direct and indirect photolysis rates for imazethapyr and to evaluate the photolysis of imazethapyr in three rice paddy waters. The reaction quantum yield (phi I) for imazethapyr was determined to be 0.023 +/- 0.002, while the hydroxyl radical rate constant (K(I)*OH) was 2.8 x 10(13) M(-1) h(-1). These results show that imazethapyr is susceptible to both direct and indirect photolysis reactions in water. The results also show that imazethapyr photolysis in paddy water will be affected by turbidity because of its impact on the availability of sunlight to drive direct and indirect photolysis reactions.