The influence of environmental factors on biotic responses to nutrients was examined in three diverse agricultural regions of the United States. Seventy wadeable sites were selected along an agricultural land use gradient while minimizing natural variation within each region. Nutrients, habitat, algae, macroinvertebrates, and macrophyte cover were sampled during a single summer low-flow period ...

the effect of levels of nitrogen on growth and nitrogen uptake patterns and grain protein quality of grain sorghum was investigated by two experiments which were conducted at pakdasht-tehran in 2003. in a completely randomized design with three replications, grain sorghum (sorghum bicolor (l.) moench) hybrid h-726 was grown under greenhouse conditions using water culture technique. the first ex...

in order to evaluate plant density and different nitrogen levels on protein percent, yield and nitrate accumulation in potato tuber cv. agria, a factorial experiment based on randomized complete block design with three replications was conducted in ardabil in 2006. factors included nitrogen levels: 0, 80, 160 and 200 kg ha-1 net nitrogen and plant densities: 5.5, 7.5 and 11 plant m-2. results s...

in recent years, surplus usage of chemical fertilizers and inattention the importance organic matter to improve soil fertility, leading to increasing use of chemical fertilizer, environmental pollution and etc. in order to study the different fertilizer levels (organic, chemical and combined) on yield of grain corn (s.c.704) experiment was conducted at the research farm faculty of agriculture t...