The impact of agricultural management on global warming potential (GWP) and greenhouse gas intensity (GHGI) is not well documented. A long-term fertilizer experiment in Chinese double rice-cropping systems initiated in 1990 was used in this study to gain an insight into a complete greenhouse gas accounting of GWP and GHGI. The six fertilizer treatments included inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), and balanced inorganic fertilizer (NPK)], combined inorganic/organic fertilizers at full and reduced rate (FOM and ROM), and no fertilizer application as a control. Methane (CH 4 ) and nitrous oxide (N 2 O) fluxes were measured using static chamber method from November 2006 through October 2009, and the net ecosystem carbon balance was estimated by the changes in topsoil (0-20 cm) organic carbon (SOC) density over the 10-year period 1999-2009. Longterm fertilizer application significantly increased grain yields, except for no difference between the NK and control plots. Annual topsoil SOC sequestration rate was estimated to be 0.96 t C ha À1 yr À1 for the control and 1.01-1.43 t C ha À1 yr À1 for the fertilizer plots. Long-term inorganic fertilizer application tended to increase CH 4 emissions during the flooded rice season and significantly increased N 2 O emissions from drained soils during the nonrice season. Annual mean CH 4 emissions ranged from 621 kg CH 4 ha À1 for the control to 1175 kg CH 4 ha À1 for the FOM plots, 63-83% of which derived from the late-rice season. Annual N 2 O emission averaged 1.15-4.11 kg N 2 O-N ha À1 in the double rice-cropping systems. Compared with the control, inorganic fertilizer application slightly increased the net annual GWPs, while they were remarkably increased by combined inorganic/organic fertilizer application. The GHGI was lowest for the NP and NPK plots and highest for the FOM and ROM plots. The results of this study suggest that agricultural economic viability and GHGs mitigation can be simultaneously achieved by balanced fertilizer application.

Previous studies demonstrated that ammonium nutrition results in higher water uptake rate than does nitrate nutrition under water stress, and thus enhances the tolerance of rice plants to water stress. However, the process by which water uptake is related to nitrogen form under water stress remains unknown. A hydroponic experiment with simulated water stress induced by polyethylene glycol (PEG6000) was conducted in a greenhouse to study the relationship between root aerenchyma formation and water uptake rate, such as xylem sap flow rate and hydraulic conductance, in two different rice cultivars (cv. 'Shanyou 63' hybrid indica and cv. 'Yangdao 6' indica, China). The results showed that root aerenchyma tissue increased in water-stressed plants of both cultivars fed by nitrate. No significant difference was found in root hydraulic conductivity and/or xylem sap flow rate between the two rice cultivars fed by ammonium regardless of water status, whereas these parameters decreased significantly in water-stressed plants fed by nitrate. It was concluded that aerenchyma that formed in the root cortex impeded the radial transport of water in the root cylinder and decreased water uptake in water-stressed rice plants fed by nitrate. Water transport occurred mainly through Hg-sensitive water channels in rice roots supplied with ammonium.

No abstract

No abstract

No abstract

Reductions in soil productivity and soil water retention capacity, and water scarcity during crop growth, may occur due to long-term suboptimal tillage and fertilization practices. Therefore, the application of appropriate tillage (subsoiling) and fertilization (organic fertilizer) practices is important for improving soil structure, water conservation and soil productivity. We hypothesize that subsoiling tillage combined with organic fertilizer has a better effect than subsoiling or organic fertilizer alone. A field experiment in Henan, China, has been conducted since 2011 to explore the effects of subsoiling and organic fertilizer, in combination, on winter wheat (Triticum aestivum L.) farming. We studied the effects of conventional tillage (CT), subsoiling (S), organic fertilizer (OF), and organic fertilizer combined with subsoiling (S+OF) treatments on dry matter accumulation (DM), water consumption (ET), water use efficiency (WUE) at different growth stages, yield, and water production efficiency (WPE) of winter wheat over 3 years (2016–2017, 2017–2018, 2018–2019). We also analyzed the soil structure, soil organic carbon, soil microbial biomass carbon and nitrogen, and soil enzymes in 2019. The results indicate that compared with CT, the S, OF and S+OF treatments increased the proportion of >0.25 mm aggregates, and S+OF especially led to increased soil organic carbon, soil microbial biomass carbon and nitrogen, soil enzyme activity (sucrase, cellulose, and urease). S+OF treatment was most effective in reducing ET, and increasing DM and WUE during the entire growth period of wheat. S+OF treatment also increased the total dry matter accumulation (Total DM) and total water use efficiency (total WUE) by 18.6–32.0% and 36.6–42.7%, respectively, during these 3 years. Wheat yield and WPE under S+OF treatment increased by 11.6–28.6% and 26.8–43.6%, respectively, in these 3 years. Therefore, S+OF in combination was found to be superior to S or OF alone, which in turn yielded better results than the CT.

No abstract

Ethylene increases root cortical aerenchyma formation in maize (Zea mays L.), rice (Oryza sativa L.) and other species. To further investigate the effects of nitrate, ammonium and water stress on ethylene production and aerenchyma formation in roots, two lowland rice cultivars (Shanyou 63, hybrid indica, and Yangdao 6, inbred indica) were cultured hydroponically with 10% (w/v) polyethylene glycol to simulate water stress. Water stress decreased shoot biomass, stomatal conductivity and leaf water potential in cultivars fed with nitrate but not with ammonium. Water stress induced more aerenchyma formation in cultivars fed with nitrate rather than ammonium, and increased cortical aerenchyma was found in Yangdao 6. Endogenous ethylene production by roots increased significantly under water stress in plants fed with nitrate rather than ammonium. Exogenous ethylene stimulated root cortical aerenchyma formation. Expression of the ethylene biosynthesis gene 1-aminocyclo-propane-1-carboxylic acid (ACC) synthase (ACS5) was greater in roots fed with nitrate rather than ammonium in the presence and absence of water stress. The expression of ethylene signalling pathway genes involved in programmed cell death (lesion-simulating disease (L.S.D.)1.1 and L.S.D.2; enhanced disease susceptibility (EDS) and phytoalexin-deficient (PAD4)) were regulated by the N form and water stress. In plants of cultivars fed with ammonium, L.S.D.1.1 expression increased under water stress, whereas L.S.D.2, EDS and PAD4 expression decreased. In conclusion, nitrate increases ethylene production and cortical aerenchyma formation in roots of water-stressed lowland rice. However, ammonium increased L.S.D.1.1 expression in water-stressed roots, and decreased ACS5, EDS and PAD4 expression, which would inhibit ethylene production and aerenchyma formation.