An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil productivity and also for restraining global warming by CO 2 evolution. Results of a long-term (30 year) experiment in the Indian Himalayas under rainfed soybean (Glycine max L.)-wheat (Triticum aestivum L.) rotation was analyzed to determine the influence of mineral fertilizer and farmyard manure (FYM) application at 10 Mg ha -1 on SOC and total soil nitrogen (TSN) stocks and distribution within different aggregate size fractions. Fertilizers (NP, NK and NPK) and FYM in combination with N or NPK were applied before the soybean crop every year and no nutrient was applied before the wheat crop. Results showed that addition of FYM with N or NPK fertilizers increased SOC and TSN contents. The overall gain in SOC in the 0-to 45-cm soil depth interval in the plots under NPK ? FYM treatment over NPK was 17.18 Mg C ha -1 in 30 year. The rate of conversion of input C to SOC was about 19% of each additional Mg C input per hectare. SOC content in large size aggregates was greater than in smaller size aggregates, and declined with decreased aggregate size. Thus, long-term soybean-wheat rotation in a sandy loam soil of the Indian Himalayas sequestered carbon and nitrogen. Soil organic C and TSN sequestration in the 0.25-to 0.1-mm size fraction is an ideal indicator of long-term C and N sequestration, since this fraction retained maximum SOC/TSN stock.

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Greenhouse and field experiments were conducted to determine the response of corn (Zea mays), barnyardgrass (Echinochloa crus-galli), common lambsquarters (Chenopodium album), large crabgrass (Digitaria sanguinalis), velvetleaf (Abutilon theophrasti), and yellow foxtail (Setaria lutescence) to RPA 201772. Barnyardgrass, large crabgrass, velvetleaf, and common lambsquarters were more susceptible than yellow foxtail to RPA 201772. Velvetleaf was the most susceptible species and rates above 18 g ai/ha of RPA 201772 controlled 100% of the population 4 wk after treatment (WAT). Percent control of all the weed species increased with increased RPA 201772 rates. In the field, the dry weights of yellow foxtail decreased as the rate of RPA 201772 increased from 0 to 210 g/ha. However, a 60% reduction of dry weight of yellow foxtail was recorded at 140 g/ha of RPA 201772 compared to the untreated check 6 WAT, whereas at 12 WAT the dry weight of yellow foxtail was reduced to only 15% because of intraspecific competition. Yellow foxtail was moderately susceptible to RPA 201772. Corn was tolerant to RPA 201772; the GR80 value was 435 g/ha in the greenhouse. The bleaching injury to corn in the field was less than 10%, and it was found only with the 210 g/ha rate of RPA 201772. This injury was temporary and the plants recovered within 2 to 3 wk. Based on the GR80 values, velvetleaf was the most susceptible, followed by common lambsquarters, large crabgrass, barnyardgrass, and yellow foxtail.

Wetting agents are mainly used to manage water repellency in soils but they do provide other benefits like increase in water retention and reduction in physiological moisture stress in plants. Experiments were conducted at the California State Polytechnic University, Pomona on a loamy sand soil situated on an 8% slope with an established turfgrass maintained under golf course fairway management conditions. The effect of cultural practices like core aerification followed by sand topdressing and application of a wetting agent in reducing runoff of irrigation water was evaluated. Runoff events after the cultural practices and the wetting agent treatment (Dispatch applied at 877 ml/ha) was repeated four times over a time period when the matric potential ranged from 15-40 kPa. An empirical formula based on Horton's equation was used to predict maximum runtime of sprinklers to prevent runoff from turf on slopes. Total irrigation runoff was calculated based on overspray, surface runoff and percolation or seepage over a specified period of time. When Dispatch was added to the irrigation water vertical movement of water was more pronounced than the control (water alone). The least runoff occurred when the soil had the highest matric potential. Dispatch treatments resulted in 43% and 55% higher total wetting surface area at 30 minutes and 60 minutes respectively compared to the water alone treatment. Cultural practices like core aerification, topdressing with sand and using a wetting agent reduced the volume of surface runoff by increasing the infiltration rate and the time period when visible surface runoff was first observed since the start of the irrigation event.