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Root water uptake is strongly influenced by the morphology and anatomical structure of roots, which are regulated by nitrogen forms and environmental stimuli. To further illustrate the roles of different nitrogen forms on root water uptake under osmotic stress, a split-root system was supplied with different nitrogen forms and osmotic stress simulated by adding 10% (w/v) polyethylene glycol (PEG, 6000). The local effects of nitrogen form and osmotic stress on root morphology, anatomical structure, root lignin content, and water uptake rate were investigated. Under osmotic stress conditions, ammonium markedly promoted the formation and elongation of the lateral root, whereas a significant decrease in numbers of lateral roots was observed under local nitrate supply. Under nitrate supply in split-root systems, osmotic stress significantly promoted root cell death and more aerenchyma formation, as well as accelerated the lignification of the root. However, osmotic stress had no negative effect on the root anatomical structure under ammonium supply. The root water uptake rate was significantly higher in split-root supplied with ammonium than nitrate under osmotic stress conditions. In conclusion, the high water uptake ability in local ammonium supply was associated with the more lateral roots development and the lower cell death, aerenchyma formation and lignification under osmotic stress. • Osmotic stress promoted lateral root development with local ammonium supplied. • Osmotic stress significantly induced aerenchyma formation in local nitrate supply. • Exceeded aerenchyma formation obviously restrict water uptake. • Ammonium could maintain a higher water uptake and increase drought resistance. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that drought resistance in rice seedlings was increased by ammonium (NH 4 + ) treatment, but not by nitrate (NO 3 − ) treatment, and that the change was associated with root development. To study the effects of different forms of nitrogen on water uptake and root growth under drought conditions, we subjected two rice cultivars (cv. ‘Shanyou 63’ hybrid indica and cv. ‘Yangdao 6’ indica , China) to polyethylene glycol-induced drought stress in a glasshouse using hydroponic culture. Under drought conditions, NH 4 + significantly stimulated root growth compared to NO 3 − , as indicated by the root length, surface area, volume, and numbers of lateral roots and root tips. Drought stress decreased the root elongation rate in both cultivars when they were supplied with NO 3 − , while the rate was unaffected in the presence of NH 4 + . Drought stress significantly increased root protoplast water permeability, root hydraulic conductivity, and the expression of root aquaporin (AQP) plasma intrinsic protein (PIP) genes in rice plants supplied with NH 4 + ; these changes were not observed in plants supplied with NO 3 − . Additionally, ethylene, which is involved in the regulation of root growth, accumulated in rice roots supplied with NO 3 − under conditions of drought stress. We conclude that the increase in AQP expression and/or activity enhanced the root water uptake ability and the drought tolerance of rice plants supplied with NH 4 + . [ABSTRACT FROM AUTHOR]

The impact of long-term fertilizer on ammonia (NH) volatilization in a double rice-cropping system is not well documented. A long-term fertilizer experiment in Chinese double rice-cropping systems initiated in 1990 was used in this study to evaluate the NH volatilization. Six fertilizer treatments were designed, including inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), and balanced mineral fertilizer (NPK)], combined inorganic/organic fertilizers at full and reduced rate (FOM and ROM), and no fertilizer application (served as control). Ammonia volatilization fluxes were measured using a continuous airflow enclosure method during double rice growing seasons from 2007 to 2009. Results showed that the cumulative NH volatilizations in the fertilizer plots ranged from 12.8 to 27.3 kg N ha for the early rice season and from 17.3 to 32.7 kg N ha for the late rice season, which accounted for 9.2-33.6 % and 17.8-32.2 % of the applied N, respectively. The NH concentration in floodwater is a predominant factor to NH losses in the double rice-cropping systems. Compared with the NPK, the cumulative NH volatilizations during double rice growing seasons were respectively increased by 9.7, 50.6, and 37.6 % for the NP, NK, and FOM plots, respectively, while they were decreased by 24.6 % for the ROM plots. Compared with the NPK, N uptakes by rice were decreased by 7.2-49.7 % with imbalanced fertilizer application (NP and NK), while they were increased by 9.6-41.0 % with combined inorganic/organic fertilizers application (ROM and FOM). Grain yields were comparable among the NPK, ROM, and FOM treatments, but they were declined by the treatments with imbalanced fertilizer application. These results suggested that agricultural economic viability and NH volatilization mitigation can be simultaneously achieved by balanced inorganic and organic fertilizers application. [ABSTRACT FROM AUTHOR]

In order to find out the appropriate measures for soil water preservation and wheat yield increase, a three–year field experiment was conducted in Yuzhou Experimental Station of Water Saving Agriculture in the west of Henan Province, China, during the growing seasons of 2014–2015, 2015–2016 and 2016–2017 to study the effects of different tillage modes and soil mulching measures on dynamics of soil moisture and temperature, photosynthetic characteristics and yield of winter wheat ( Triticum aestivum L .). The results showed that straw coverage and film mulching measures under the conventional tillage and no tillage modes increased soil moisture by 4.4%–27.3%,13.4%–41.8% and 6.2%–46.7%, 2.4%–80.2%, respectively. The treatments of soil surface coverage measures under both conventional tillage and no tillage modes at tillering stage increased the temperature of soil layer at 10 cm and 15 cm depth by 9.1%–18.2% and 10.0%–40.0% in 2014–2015, while mulching measures under the conventional tillage obviously increased soil temperature at wintering stage but decreased soil temperature at booting and mature stages in 2016–2017. However, mulching measures under no tillage mode reduced soil temperature in shallower layer during seedling establishment stage in the three–year period of 2014–2017. Moreover, the two mulching measures raised net photosynthetic rate (Pn) and water use efficiency (WUE) of functional leaves under the conventional tillage mode and reduced transpiration rate (Tr) at the filling stage. Except straw coverage measures under no tillage in 2015–2016, the combination of mulching measures under no tillage reduced Pn, Tr and WUE of wheat leaves at filling stage as compared to those without mulching measures. Under the conventional tillage mode, straw coverage increased wheat yield by 6.4%–9.3%, mainly due to the increase in the number of grains per panicle. Under no tillage mode, both straw coverage and mulching measures reduced wheat yield to different extents and film mulching measures was more effective than straw coverage. The combination of conventional tillage and straw mulching resulted in a yield of 8425.9–8888.9 kg hm −2 , so this combination was recommended as the optimal treatment under the conditions set in this study. [ABSTRACT FROM AUTHOR]

Tillage combined with straw mulching is an effective water-saving agricultural strategy in eastern Central China. A two-year field experiment with four treatments, including conventional tillage (CT), conventional tillage with straw mulching (CT+S), no-tillage (NT) and no-tillage with straw mulching (NT+S), was conducted on semihydromorphic soil. The objective was to investigate how tillage with straw mulching affected the soil temperature, water consumption, photosynthetic rate (Pn), grain yield, soil temperature use efficiency (TUE) and water productivity (WP) in a winter wheat-summer maize rotation system. The results indicated that straw mulching tended to increase the soil temperature before the wheat regreening stage and decrease the soil temperature during the following wheat growing season and throughout the maize growing season. Compared with CT, the soil effective accumulated temperature (EAT) under the NT+S treatment significantly decreased by 4.8% but the annual ET increased by 4.3% in the winter wheat–summer maize rotation system. The Pn and transpiration rate (Tr) at the anthesis stage of wheat under the NT+S treatment increased by 15.2% and 15.6%, respectively, and the leaf water use efficiency (LWUE) during the growing season of maize increased by 11.3% as compared with that under CT treatment. Wheat yields decreased in the order of NT+S, NT, CT and CT+S during both experimental years, and the average yield of maize under the NT+S treatment increased by 27.2% compared with that under CT. Additionally, WP values under the NT+S treatment during both the wheat and maize seasons were 7.0% and 21.8% higher than those of the CT treatment (p < 0.05), respectively. The annual yield, TUE and WP values under the NT+S treatment were much higher than those under the other treatments. Therefore, NT+S treatment has a positive effect on yield and hydrothermal resource utilization in semihydromorphic soil in eastern Central China. • NT+S improved annual crop yield by 19.5% compared to conventional tillage. • NT+S increased hydrothermal resources utilization in this rotation system. • NT+S enhanced LWUE of the wheat and maize in eastern central China. [ABSTRACT FROM AUTHOR]

• SAP and OM improved soil structure and increased organic carbon content. • SAP incresed the TOC and LOC of 0.25-2.0 mm aggregates at the 10-40 cm depth. • Soil structural stability of SAP was significantly higher than that of OM at 0-10 cm depth. Super absorbent polymer (SAP) and organic manure (OM) may improve soil structure and change soil organic carbon (SOC) composition and agroecosystem functioning. However, the understanding of the effects of SAP and OM on SOC composition, specifically in deeper soil layers, is still not clear. The objectives of this study were to examine the effects of long-term application of SAP and OM (8 years) on changes in SOC and soil structure down to a soil depth of 100 cm. Therefore, in order to investigate the stability of soil structure and the distribution of organic carbon at different soil depths (0-10 cm, 10-20 cm,..., 90-100 cm) under long-term application of SAP, OM, and a control treatment, soil structure and soil organic carbon content were analyzed in mixed soil samples and undisturbed soil samples. The results indicated that with depth, the proportion of large aggregates (0.5-2.0 mm) decreased gradually, while the proportion of small aggregates (<0.25 mm) increased gradually. Compared with the control, SAP treatment was conducive to the increment of>0.5 mm soil aggregates in the 0-30 cm and 40-60 cm soil layers (P < 0.05) and 0.25-0.5 mm in the 0-50 cm soil layer (P < 0.05), and while the OM treatment had the same effect in the 0-30 cm soil layer (P < 0.05). The total organic carbon content (TOC) and labile organic carbon content (LOC) of bulk soil increased (0-20 cm) initially with depth, and then decreased (20-70 cm) approximately. In the 0-50 cm soil layer, the TOC and LOC under SAP treatment were higher than those under OM treatment. The SAP treatment was more beneficial to the increase of the TOC and LOC of 0.5-2.0 mm and 0.25-0.5 mm aggregates in the 10-40 cm soil layer compared with the control and OM treatment (P < 0.05). The SAP treatment was also more beneficial in increasing the contribution rate of organic carbon (CROC) in> 0.5 mm aggregates in 0-40 cm soil depth, while the OM treatment was more beneficial in increasing the CROC of > 0.5 mm aggregates in 0-30 cm soil depth. The SAP treatment improved the stability of the soil structure in 0-30 cm and 40-60 cm depths, and the OM treatment had the same effect in the 0-30 cm depth. Compared with the control and OM treatments, SAP treatment has shown to be the most beneficial in improving soil structure and increasing organic carbon content. [ABSTRACT FROM AUTHOR]