The aim of this study was to analyze the influence of organic fertilizer on the availability of natural food (plankton and benthos) and water quality. Two fertilization protocols were adopted using inorganic and organic fertilizers with shrimp (stocked treatment) and their controls (unstocked treatment). Experimental units consisted of 12 circular fiberglass tanks (500 l) with estuarine sediment, individual aeration and no water exchange. In stocked treatments were used 40 juveniles/m², and they were fed with 35% crude protein marine shrimp ration, three times a day. Under the organic fertilization protocol, the plankton showed higher abundance of Nitzschia and rotifers, the phytobenthos consisted mainly of Nitzschia, Amphiprora and Oscillatoria, the epibenthos was represented mainly by nematodes and rotifers, and the macro-invertebrates were mainly oligochaetes. In relation to inorganic fertilization, the plankton was represented mainly by Coscinodiscus and rotifers, the phytobenthos consisted mainly of Amphiprora and Oscillatoria, the epibenthos was represented mainly by nematodes and rotifers, and the macro-invertebrates were mainly oligochaetes. Dissolved oxygen was higher for organic fertilizer (6.16 ± 0.98 mg/l) than for inorganic (5.92 ± 1.19 mg/l) while the other water quality parameters did not present significant differences. Survival was similar in the two fertilization regimes (96.6%). Final body weight was 11.89 ± 1.73 g for the inorganic fertilizers and 12.28 ± 1.71 g for organic fertilizer. It is concluded that wheat bran showed good performance in the water quality without exchange, in the availability of natural food, and in the growth and survival of the shrimps in the microcosms.

Rapid intensification of Vietnamese rice production has had a positive effect on the nation's food production and economy. However, the sustainability of intensive rice production is increasingly being questioned within Vietnam, particularly in major agricultural provinces such as An Giang. The construction of high dykes within this province, which allow for complete regulation of water onto rice fields, has enabled farmers to grow up to three rice crops per year. However, the profitability of producing three crops is rapidly decreasing as farmers increase their use of chemical fertilizer inputs and pesticides. Increased fertilizer inputs are partly used to replace natural flood-borne, nutrient-rich sediment inputs that have been inhibited by the dykes, but farmers believe that despite this, soil health within the dyke system is degrading. However, the effects of the dykes on soil properties have not been tested. Therefore, a sampling campaign was conducted to assess differences in soil properties caused by the construction of dykes. The results show that, under present fertilization practices, although dykes may inhibit flood-borne sediments, this does not lead to a systematic reduction in nutrients that typically limit rice growth within areas producing three crops per year. Concentrations of total nitrogen, available phosphorous, and both total and available potassium, and pH were higher in the surface layer of soils of three crop areas when compared to two crop areas. This suggests that yield declines may be caused by other factors related to the construction of dykes and the use of chemical inputs, and that care should be taken when attempting to maintain crop yields. Attempting to compensate for yield declines by increasing fertilizer inputs may ultimately have negative effects on yields.

Exploring interactions between factors is a critical step to understand, quantify and govern the WEF-Nexus. However, current research mainly focuses on mapping causal loops and the hierarchy structure; equations in interaction exploration have been largely ignored. Using the panel data of China’s 30 provinces from 2005 to 2016, this paper adopts a simultaneous equations model (SEM) to evaluate intensities between related factors in the local WEF-Nexus. We define a local WEF-Nexus as containing core, peripheral and interactive sub-nexuses, and decouple the core sub-nexus from the supply, consumption and waste disposal processes. Results show that effective irrigated area, secondary industry rate and crop sown area are key positive influencing factors in the WEF subsystem, with positive impact coefficients of 1.0426, 0.6986 and 1.149, respectively. Food production (-0.303) and chemical fertilizer used per sown area unit (-0.3129) are key negative factors in the WEF subsystem. Additionally, urban green land (0.4436) and total population (0.5815) exert specific influences on the water and energy subsystems, with a 1% increase in urban green land resulting in a 0.4436% increase in water consumption. The system boundary, two positive feedback loops and seven nexus points are identified, with total groundwater pumping being the only nexus point exerting an holistic impact across the WEF equations. The results in this paper complement recent nexus modeling work, and give a better understand of interaction mechanism in China’s local WEF nexus, with useful implications for future policy development.

The waste management as the interface between human daily life and environment is an important part in rural region. However, the micro-scale process analysis from the perspective of an integrated rural water-food-energy system has not been well investigated to reveal the effects brought by waste management on local environment. The lack of relevant evidence is a major barrier to realize the specific quantitative impacts of distinct waste management systems and the importance of sustainable waste management for local area. In this study, a material and energy flow analysis based on processes is presented in a micro-scale to make systematical comparison between end-pipe-treatment waste management and modern resource-oriented waste management. The results indicated that waste management notably affects the nitrogen and phosphorus flow in rural areas. Moreover, the resource-oriented system can obviously optimize the local water-food-energy nexus in terms of energy recovery and nutrient consumption. Based on the quantity analysis, chemical fertilizer is also found inevitable to guarantee the food supply because of the element system loss in various paths. Besides, the simultaneous optimum point of different nutrient elements is difficult to achieve due to their distinct transfer mechanisms. Our results can help policymakers and publics make better choice in waste management strategy.

Sustainable management of natural resources under economic, environmental and social perspective, needs to consider a fair balance between its uses and availability. Sustainable agriculture goal is to establish innovative and new farm tools and service capacities that help the intensive farm sector to optimize input management (energy, nutrients and water) and productivity. The main objective of this paper was to investigate, in a durum wheat production system in central Italy under Mediterranean conditions, the following aspects: (i) environmental sustainability of fertilization treatments through the energy inputs/outputs analysis and reduction of Nitrate (N-NO₃) in water cycle; (ii) agricultural system agronomic and economic performance and (iii) to identify regulatory and economic instruments actually in place to promote sustainable fertilization. To describe and address the sustainability assessment of durum wheat production system we adopt the “Water Energy Food nexus” (WEF) as conceptual framework. The findings of this research showed that there is a great difference between the marketable yields obtained with mineral fertilization strategies and those by organic fertilizer, while considering the environmental sustainability, our results provide evidences of the significance of the reduction of energy use and the high value of renewable energies and the decreasing of non-renewable one. At the same time the reduced impact of groundwater quality due to the organic fertilizer seems to be an interesting result to be analyzed in the long-term perspective. The contraposition between economy and environment is one of the main challenges to be solved through adequate policy instruments.