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Quantitative evaluation of the effects of diverse greenhouse vegetable production systems (GVPS) on vegetable yield, soil water consumption, and nitrogen (N) fates could provide a scientific basis for identifying optimum water and fertilizer management practices for GVPS. This research was conducted from 2013 to 2015 in a greenhouse vegetable field in Quzhou County, North China. Three production systems were designed: conventional (CON), integrated (INT), and organic (ORG) systems. The WHCNS-Veg model was employed for simulating vegetable growth, water dynamics, and fates of N, as well as water and N use efficiencies (WUE and NUE) for four continuous growing seasons. The simulation results revealed that nitrate leaching and gaseous N emissions constituted the predominant N loss within GVPS, which separately accounted for 11.5–59.4% and 6.0–21.1% of the N outputs. The order of vegetable yield, N uptake, WUE, and NUE under different production systems was ORG > INT > CON, while the order of nitrate leaching and gaseous N loss was CON > INT > ORG. Compared to CON, ORG exhibited a significant increase in yield, N uptake, WUE, and NUE by 24.6%, 24.2%, 26.1%, and 89.7%, respectively, alongside notable reductions in nitrate leaching and gaseous N loss by 67.7% and 63.2%, respectively. The ORG system should be recommended to local farmers. [ABSTRACT FROM AUTHOR]

Global warming is widely expected to alter nitrogen (N) cycling in terrestrial ecosystems by accelerating N transformations in soils. However, it is unclear how warming will affect plant–soil N cycling in subtropical ecosystems.Here, we measured the N transformations including net ammoniation, nitrification, nitrous oxide emissions and nitrate in soil solution throughout the plant–soil continuum with 2 years of experimental soil warming (+5°C) in a young subtropical Chinese fir mesocosm. Seasonal variations of soil and plant (foliage and root) N concentrations and isotopes (δ15N), foliar water use efficiency and arbuscular mycorrhizal colonization rate were measured.Soil warming significantly increased net ammonization and nitrification of the soil, together with the transient positive response observed in inorganic N of the soil. Warming increased nitrate N fluxes in soil solution and nitrous oxide emissions in the first year but not in the second year, suggesting N losses through leaching and gaseous in the initial period of warming. Warming primarily induced enrichment of 15N in foliage relative to the soil, which was attributed to the trade‐offs of persistent increases in plant N uptake caused by enhanced tree growth and a decrease in N losses with continuous warming. Furthermore, young trees' growth and N uptake capacity can rapidly acclimate to climate warming as a result of warming‐induced increases in arbuscular mycorrhizal colonization and foliar water use efficiency.Our findings highlight that warming accelerates the plant–soil N cycle and promotes young trees' growth and N uptake, which in turn reduces soil N lost from this subtropical ecosystem. Therefore, our study suggests that the competition for N between plants and microbes governs whether subtropical forests are opened or closed N cycle systems under climate warming. We predict that subtropical young forests can still maintain their high productivity because young trees can maintain their N uptake capacity and adequate soil N supply in facing future climate warming. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Quantitative evaluation of the effects of diverse greenhouse vegetable production systems (GVPS) on vegetable yield, soil water consumption, and nitrogen (N) fates could provide a scientific basis for identifying optimum water and fertilizer management practices for GVPS. This research was conducted from 2013 to 2015 in a greenhouse vegetable field in Quzhou County, North China. Three production systems were designed: conventional (CON), integrated (INT), and organic (ORG) systems. The WHCNS-Veg model was employed for simulating vegetable growth, water dynamics, and fates of N, as well as water and N use efficiencies (WUE and NUE) for four continuous growing seasons. The simulation results revealed that nitrate leaching and gaseous N emissions constituted the predominant N loss within GVPS, which separately accounted for 11.5–59.4% and 6.0–21.1% of the N outputs. The order of vegetable yield, N uptake, WUE, and NUE under different production systems was ORG > INT > CON, while the order of nitrate leaching and gaseous N loss was CON > INT > ORG. Compared to CON, ORG exhibited a significant increase in yield, N uptake, WUE, and NUE by 24.6%, 24.2%, 26.1%, and 89.7%, respectively, alongside notable reductions in nitrate leaching and gaseous N loss by 67.7% and 63.2%, respectively. The ORG system should be recommended to local farmers.

Highlights: [•] The EU-Rotate_N model was validated for greenhouse tomato in Northern China. [•] Nitrate leaching and gaseous N loss are the main pathways of N loss. [•] Optimal fertilizer and drip irrigation can significantly reduce nitrate leaching. [•] Adding crop residues can reduce nitrate leaching. [•] Evaluating and optimizing the combinations of water and fertilizer practices [ABSTRACT FROM AUTHOR]

Abstract: Land application is a common method for treatment and disposal/reuse of process water and solids from food processing in Central Valley California, USA. Application rates are commonly based on N as contamination of ground and surface waters are of environmental concern. Contemporary disposal practices employ a crop to consume the N applied. Tomato processing wastewaters and semi-solid wastes were evaluated using homogeneous soil columns, and long-term monitoring of the cannery land application site. The 105-day outdoor column study included the smectitic field soil of clay loam texture, Bermudagrass, and three cannery water (CW) loading rates and a control (urea) applied weekly. NO3 − and BOD leaching were low during the simulated irrigation season. Based on N grass uptake, leaching losses, and soil N, gaseous N losses were 50, 64, and 61% of the N applied from 313, 471, and 627kgNha−1 CW applications. However, gaseous N losses exceeded N applied by all treatments and included significant native soil N loss ranging from 1500 to 2600kgha−1. N losses indicated a “priming effect” due to mineralizable organics, and a significant decrease in soil C was seen in all treatments. The study results point toward denitrification as the major cause of gaseous N losses where ammonia volatilization was found to be a lessor cause of N loss. Long-term field monitoring results showed greater N impacts from land incorporation of semi-solid wastes than from wastewater irrigation, consistent with the soil column findings. The study demonstrated that CW having high amounts of labile organics applied to a soil of low permeability can result in heightened gaseous N loss rates, especially by denitrification. Gaseous N losses in addition to crop N uptake lessened the possibility of contamination of ground and surface waters. [Copyright &y& Elsevier]

Mean dissolved inorganic nitrogen concentrations ([DIN]) in deep, seasonally stratified lakes with comparable DIN inputs can differ by up to a factor of 3 depending on hydraulic and morphometric properties and/or different trophic states of the lakes. In such lakes, net N sedimentation rates were estimated with two independent methods (sediment core analysis and input-output mass balances). They were higher in eutrophic lakes (Mean: 5.1; SD: ± 1.6 g m yr; n = 13) than in oligotrophic lakes (1.6 ± 1.0 g m yr; n = 3), but independent of [DIN]. Gaseous N loss rates to the atmosphere, as calculated from combined N- and P-mass balances from selected lakes, ranged from 0.9 to 37.4 g m yr (n = 10) and were positively correlated with [DIN]. Reduction of NO to N is assumed to be the main cause for gaseous N losses. A simple one-box mass balance model for [DIN], based on DIN input and rates and kinetics of N removal processes (net sedimentation and gaseous N loss) is proposed, and validated with a data base on [DIN] and DIN input in 19 deep, seasonally stratified lakes of central Europe. The model illustrated that the amount of water loading per unit surface area of a lake (called water discharge height q) is the critical parameter determining mean lake [DIN] relative to mean input [DIN]. Lakes with a q > 50 m yr have average [DIN] similar to the [DIN] of the inflows regardless of their trophic states, because input and outflow exceed lake-internal N removal processes. A high primary production favors DIN removal in lakes with q < 50 m yr. It is concluded that measures to decrease primary production, e.g. by means of P removal programs, lead to an increase of [DIN] in lakes. [ABSTRACT FROM AUTHOR]

Denitrification of nitrate in the soil can be a mechanism of significant loss of fertilizer and soil nitrogen, but it can also serve to remove excess NO3- that is leached below the root zone. Inappropriate management of irrigation water and fertilizer N in irrigated corn has resulted in leaching of excess N from the rooting zone and contamination of groundwater and also has contributed to the increasing concentration of N2O in the atmosphere. Denitrification can be both microbial and chemical, but the microbial process dominates in most soils through a stepwise reduction of NO3- to N2 . Soil atmosphere O2 concentration, which is regulated by soil water content interactively with soil texture and microbial respiration, is the main controller of the process. The oxygen consumption rate depends on the amount of easily degradable organic C compounds and the interplay of water and carbon in developing in the soil reduced oxic conditions, which regulate not only the amount of total denitrification but also the ratio of N2O to N2 produced. Appropriate management of nutrient input, relative to crop demand and soil water status, can limit nitrogen loss from denitrification. This paper describes the role of denitrification in the nitrogen economy of crop production and the environment, describes the process involved, and presents suggestions for limiting N loss caused by denitrification. [ABSTRACT FROM AUTHOR]