Milk production has greatly increased in China recently, with significant impacts on the cycling of nitrogen (N) and phosphorus (P). However, nutrient flows within the changing dairy production system are not well quantified. The aim of this study was to increase the quantitative understanding of N and P cycling and utilization in dairy production through database development and simulation mod...

Three alternatives for integrating a solar field with the bottoming cycle of a combined cycle plant are modeled: parabolic troughs with oil at intermediate and low cycle pressures and Fresnel linear collectors at low cycle pressure. It is assumed that the plant will always operate at nominal conditions, using post-combustion during the hours of no solar resource. A thermoeconomic study of the o...

Comparisons of stocking rates across sites can be facilitated by calculating grazing pressure. We used peak standing crop and stocking rates from six studies in the North American Great Plains (Cheyenne, Wyoming; Cottonwood, South Dakota; Hays, Kansas; Nunn, Colorado; Streeter, North Dakota; and Woodward, Oklahoma) to calculate a grazing pressure index and develop relationships for harvest effi...

This contribution examines various flow measures based on analysis of 41 quantified models of trophic interactions in aquatic ecosystems. System productivity/biomass ratio is shown to relate to ecosystem maturity and to the degree of cycling in the systems. Distinct patterns or clusters are observed for different types of resource systems with respect to average path lengths and residence times...

introduction with the continuous growth of world population, degradation and ecological imbalance throughout the world, there is a need to increase agricultural production and environmental protection measures. in this respect, efforts to supply nutrients to the environment are at the head of the programs. one of the ways to approach this goal is the use of intercropping systems (najafi & moham...

Background Microorganisms govern important ecosystems processes, in particular the degradation of organic matter (OM). However, microorganisms are rarely considered in efforts to monitor ecosystem health and functioning. Evidence suggests that environmental perturbations can adversely affect microbial communities and their ability to use available substrates. However, whether impacted microbial...

introduction conventional operations in fields, soil and water management are not efficient and loss of and damage to the environment are considerable (lal, 2000). crop diversity and understanding the complex interactions between environmental and socioeconomic factors are approaches to make better use of limited resources (tengberg et al., 1998). the most diverse ecosystems have a higher produ...

Poor irrigation water management is one of the major factors limiting crop production inEthiopia. This study was, therefore, conducted at three different locations in the southeasternEthiopia for 2 consecutive years to investigate the effects of different irrigation depths andintervals with furrow irrigation system on tuber yield, biomass yield and water use efficiency ofpotato. The treatments ...

This paper attempts to identify sources of resource use inefficiency for cotton production in Pakistan’s Punjab. The use of a non-parametric method, Data Envelopment Analysis (DEA), is developed to study the relative technical and allocative efficiencies of individual farms which use similar inputs, produce the same product and operate under comparable circumstances. In the ‘cotton–wheat’ syste...