Maize (Zea mays L.) production requires large amounts of nitrogen (N) that directly affect production cost. Poultry litter can be used as an alternative source of N. To optimize its use, poultry litter requires technical and economic feasibility analyses. Crop simulation models have proven to be efficient tools to support this type of research. The objectives of this study were to determine yield and net return of maize production fertilized with both mineral fertilizer and poultry litter. High inter-annual variation was observed in simulated yield for all fertilization strategies evaluated. The higher the mineral N rate, the higher the yield. Among the treatments fertilized with poultry litter the highest yield was obtained with a rate equivalent to 240 kg ha-1 of N. The trend of the economic net return for the different rates of mineral fertilizers was in the opposite direction of the trend in yield, i.e., the higher the rate of mineral fertilizer, the lower the economic return. Among the poultry litter fertilization strategies, the average economic net return increased up to a rate equivalent to 210 kg ha-1 of N, decreasing for higher rates. Poultry litter rates equivalent to 120 to 300 kg ha-1 of N, economically exceeded all the mineral fertilization strategies that were evaluated. Among all sources and rates, the highest net return was obtained for a rate of 210 kg ha-1 of N as poultry litter. Higher rates provided a lower net return and increased the likelihood of nitrate leaching.

Introduction Currently, many disasters threaten the health of ecosystems. The pressures caused by extensive human interventions and the unprincipled exploitation of natural resources have led to the degradation of natural resources and the structure and functioning of ecosystems. Hence, evaluating the consequences of human intervention in nature and meeting the growing need of humans to receive diverse services has made it necessary to evaluate the performance of watershed ecosystems in providing different services. Healthy watersheds play an important role in providing a wide variety of ecosystem services. Therefore, watershed health monitoring and evaluation is vital for the conservation of ecosystems and achieving the optimal level of services. In such a way a suitable collaborative and executive approach is established between research and watershed management. In this connection, watershed health analysis can provide valuable help in achieving the goals of integrated management of watersheds and, of course, the balance between the needs of human societies and ecosystems. However, the assessment of the health and sustainability of the watershed affected by human activities has not been sufficiently documented yet. Materials and Methods The current pilot research has evaluated the health of the Shiraz Darwazeh Quran Watershed in Fars Province, Iran, and the effect of existing watershed management structures in the region on the health of the watershed with a focus on floods. For this purpose, 36 key criteria from a set of climatic, anthropogenic, and hydrologic factors were identified based on the conditions of the region and the analysis of the flood occurrence process in the watershed. The selected criteria were then categorized into the three indices of pressure (P), state (S), and response (R). After screening the selected criteria in exploring the conceptual approach of pressure, state, and response (PSR), the health status was evaluated in two cases with and without watershed management structures. Results and Discussion The results showed that the health condition without considering the watershed management structures was at average conditions with health index of 0. 55. In addition, the results of the watershed health assessment verified the non-significant effects of stone and mortar structures on improving watershed health. So that, the health conditions was remained at average status with health index of 0. 53. Therefore, it can be acknowledged that the existing watershed management structures, due to the limited both number and spatial coverage, have not been able to noticeably affect the improvement of the general conditions of the watershed, despite the effect on the factors affecting the health of the sub-watersheds where the structures have been constructed. The spatial changes of the calculated variables showed that the abandoned lands, time of concentration, area under military activities, surface of sensitive formations to erosion, high density of the drainage network, density of the roads, areas of regions with high potential in producing runoff and sediment, and size of the residential areas were the most important factors affecting the health situation of the Darwazeh Quran Watershed. Conclusion According to the results of the analysis of the indicators and criteria considered in evaluation of the health of the Shiraz Darwazeh Quran Watershed based on the PSR approach, it was found that the watershed had an average health status. Therefore, it can be acknowledged that the existing watershed management structures have not been able to impose a noticeable effect on the prosperity and improvement of watershed health conditions. In general, it can be said that abandoned lands, short concentration time, military activities, the presence of formations sensitive to erosion, high density of drainage network and road, and the potential of high runoff and sediment production, and the size of residential areas are among the most important factors affecting the declining the health of Darwazeh Quran Watershed. Therefore, it is necessary to pay further attention to the aforesaid factors by conducting periodical monitoring with more comprehensive data, in time and also analyzing the trend of relative changes of the indicators in order to explain the adaptive and intelligent management of the watershed. The necessary measures should also be taken into account simultaneously. Therefore, it is suggested to turn the weak points of the region into strong points by applying bioengineering measures and use the opportunities in the region such as the potential of tourism and ecological features in order to improve the health status of the watershed.