Yuegao Hu

Effects of water-saving superabsorbent polymer on antioxidant enzyme activities and lipid peroxidation in corn (Zea mays L.) under drought stress

BACKGROUND Drought stress significantly limits oat (Avena sativa L.) growth and productivity. Thus an efficient management of soil moisture and study of metabolic changes in response to drought are important for improved production of oat. The objective was to gain a better understanding of drought tolerance mechanisms and improve soil water management strategies using water-saving superabsorbent polymer (SAP) at 60 kg ha(-1) under three irrigation levels (adequate, moderate and deficit) using a new type of hydraulic pressure-controlled auto irrigator. RESULTS The results showed that the relative water content and leaf water potential (ψ(1) ) were much higher in oats treated with SAP. Although the SAP had little effect on plant biomass accumulation under adequate and moderate irrigation, it significantly increased the biomass by 52.7% under deficit irrigation. Plants treated with SAP under deficit irrigation showed a significant decrease in superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase activities in leaves compared with control plants. CONCLUSION Our results suggested that drought stress leads to production of oxygen radicals, which results in increased lipid peroxidation and oxidative stress in the plant, and the application of SAP could conserve soil water, making same available to plants for increased biomass accumulation and reduced oxidative stress especially under severe water stress.

Effectiveness of a water-saving super-absorbent polymer in soil water conservation for corn (Zea mays L.) based on eco-physiological parameters

BACKGROUND The objective was to study soil water conservation and physiological growth of corn (Zea mays L.) using water-saving super-absorbent polymer (SAP) at 30 kg ha(-1). The effectiveness of SAP was studied under three irrigation levels (adequate, moderate and deficit) using a new type of negative hydraulic pressure controlled auto-irrigator in the years 2009 and 2010 in a greenhouse at Beijing, P.R. China. RESULTS Eight weeks after sowing, plant height and leaf area increased significantly by 41.6 and 79.6% under deficit irrigation for SAP treatment. The SAP had little effect on shoot dry mass under adequate and moderate irrigation but increased it significantly by 133.5% under deficit irrigation. Similarly, the efficiency of water use also increased by 97.1%. Leaf water potential under adequate and moderate irrigation differs slightly for SAP application, whereas under deficit irrigation the values were exceeded significantly by 27.8%. The superior growth and water use efficiency of corn treated with SAP under deficit irrigation was ascribed to maintenance of higher relative water contents in leaves as well as intercellular carbon dioxide concentration, net photosynthesis and transpiration rate. CONCLUSIONS Our results suggested that plant growth and different physiological activities are restricted by drought stress and the application of super-absorbent polymer could conserve soil water, making same available to plants for increased growth and biomass accumulation especially under severe water stress. Thus, application of SAP is a suitable soil management practice for the locations characterised by severe water stress.

A lysimeter study of nitrate leaching, optimum fertilisation rate and growth responses of corn (Zea mays L.) following soil amendment with water-saving super-absorbent polymer

BACKGROUND Nitrate leaching and the resulting groundwater contamination from intensive cereal production has become a major concern for long-term farmland efficiency and environmental sustainability in northern China. The aim of this study was to evaluate a water-saving super-absorbent polymer (SAP) for minimising NO(3)(-) leaching from soil and optimising corn growth and yield. Thirty-six undisturbed soil lysimeters were installed in a field lysimeter facility in drought-affected northern China to study the growth and yield characteristics of summer corn (Zea mays L.) as well as the amount of NO(3)-leaching losses under different fertiliser (standard, medium or 75% and low, or 50% of conventional fertilisation rate) and SAP (control, 0; level-1, 15 kg ha(-1) and level-2, 30 kg ha(-1)) treatments. RESULTS Corn yield fell by 19.7% under medium and 37.7% under low fertilisation; the application of SAP increased yield significantly by 44.4% on level-1 and 80.3% on level-2. Similarly, plant height, leaf area, number of grains as well as protein, soluble sugar and starch contents in the grain also increased with SAP treatment. Application of SAP at 30 kg ha(-1) plus half of conventional fertilisation can reduce maximum (64.1%) nitrate leaching losses from soil. CONCLUSIONS Application of SAP at 30 kg ha(-1) plus only half the amount of conventional fertiliser rate (150 kg urea, and 50 kg each of superphosphate and potassium sulfate) would be a more appropriate practice both for minimising nitrate leaching and sustainable corn production under the arid and semiarid conditions of northern China.

Rhizodeposition of nitrogen and carbon by mungbean (Vigna radiata L.) and its contribution to intercropped oats (Avena nuda L.).

Compounds released by mungbean roots potentially represent an enormous source of nitrogen (N) and carbon (C) in mungbean-oat intercropping systems. In this study, an in situ experiment was conducted using a 15N - 13C double stem-feeding method to measure N and C derived from the rhizodeposition (NdfR and CdfR) of mungbean and their transfer to oats in an intercropping system. Mungbean plants were sole cropped (S) or intercropped (I) with oat. The plants were labeled 5 weeks after planting and were harvested at the beginning of pod setting (Ip and Sp) and at maturity (Im and Sm). More than 60% and 50% of the applied 15N and 13C, respectively, were recovered in each treatment, with 15N and 13C being quite uniformly distributed in the different plant parts. NdfR represented 9.8% (Sp), 9.2% (Ip), 20.1% (Sm), and 21.2% (Im) of total mungbean plant N, whereas CdfR represented 13.3% (Sp), 42.0% (Ip), 15.4% (Sm), and 22.6% (Im) of total mungbean plant C. When considering the part of rhizodeposition transferred to associated oat, intercropping mungbean released more NdfR and CdfR than mungbean alone. About 53.4–83.2% of below-ground plant N (BGP-N) and 58.4–85.9% of BGP-C originated from NdfR and CdfR, respectively. The N in oats derived from mungbean increased from 7.6% at the pod setting stage to 9.7% at maturity, whereas the C in oats increased from 16.2% to 22.0%, respectively. Only a small percentage of rhizodeposition from mungbean was transferred to oats in the intercropping systems, with a large percentage remaining in the soil. This result indicates that mungbean rhizodeposition might contribute to higher N and C availability in the soil for subsequent crops.

LEAF PHOTOSYNTHESIS, BIOMASS PRODUCTION AND WATER AND NITROGEN USE EFFICIENCIES OF TWO CONTRASTING NAKED VS. HULLED OAT GENOTYPES SUBJECTED TO WATER AND NITROGEN STRESSES

Water and nitrogen (N) are the two most important factors influencing the growth and yield of oat (Avena sativa). A pot culture study was conducted to determine the physiological and biomass production of contrasting oat genotypes to water and N supply conditions. With sufficient water, biomass yield of the naked ‘Shadow’ was 12.4% and 10.0% greater than ‘Bia’ in the treatments 750 and 1250 mg N pot−1, respectively, but ‘Bia’ produced greater grain yield than ‘Shadow’. Under severe water stress conditions, increasing N supply decreased PN mainly due to the reduction of gs and E. ‘Shadow’ had higher chlorophyll and leaf N than ‘Bia’, while there were no differences in plant total N, NuptE and NUE. With increasing N application and water stress, WUEL and WUEP both increased. NUE was inversely related with increasing N rates and water stress levels, resulting in a trade-off relationship between WUEP and NUE.

Characterization of nitrogen and water status in oat leaves using optical sensing approach

BACKGROUND Optical sensing is a potential tool to estimate plant N status, but soil water deficits may interefere with forming a clear relationship. A greenhouse study was conducted with oat plants treated with three water regimes and four N levels to determine whether optical sensing could be used to estimate leaf N and relative water content (RWC). RESULTS Leaf N was strongly correlated with reflectance at 550 nm and at around 705 nm, and N treatments caused a red-edge peak shift to lower wavelength. The ratio of the first derivative reflectance at 741-696 nm (FDRE) was identified to be a good estimator of leaf N at jointing (R(2) = 0.90) and heading (R(2) = 0.86) stages across water treatments. Leaf N also had a stronger association with the red-edge position (REP) at both stages (R(2) = 0.83 and 0.78), or with the ratio R4 (R760/R550) at jointing (R(2) = 0.88), than with chlorophyll meter (SPAD) readings. Under water stress, the predictive accuracy of leaf N increased with these reflectance indices, but decreased using SPAD readings. CONCLUSION The results indicate that specific reflectance indices of FDRE, REP and R4 may be used for a rapid and non-destructive estimation of oat plant N status over a range of water regimes.

Fertilizer use efficiency of drought-stressed oat (Avena sativa L.) following soil amendment with a water-saving superabsorbent polymer

Abstract In arid and semiarid regions of northern China, there is an increasing interest in using reduced rates of chemical fertilizer along with water-saving superabsorbent polymer for field crop production. Field experiments were conducted during the year 2009 and 2010 to study the growth performance and yield characteristics of forage oat (Avena sativa L.) as well as soil moisture and nutrient status of the experimental field under different fertilizer (standard, 300; medium, 225; and low, 150 kg ha−1) treatments with (60 kg ha−1) or without application of superabsorbent polymer. Our results show that above-ground biomass accumulation fell by 14.8% under medium and 32.6% under low fertilizer levels whereas application of superabsorbent polymer increased it significantly by 39.7%. Similarly plant height, tiller fertility rate, grain yield, relative water content in the leaves as well as quality of forage also increased for superabsorbent polymer treatment. Considering the trends of growth reduction (qualitative and quantitative) due to fertilizer reduction and progressive influence of superabsorbent polymer on those parameters, it was clear that application of superabsorbent polymer plus only half the conventional fertilizer rate (150 kg ha−1) would be a more appropriate practice for forage oat production under arid and semiarid conditions of northern China or in areas with similar ecologies.

Ammonia-oxidizing archaea and bacteria responding differently to fertilizer type and irrigation frequency as revealed by Illumina Miseq sequencing

PurposeAmmonia oxidation, the first and rate-limiting step of nitrification, can be strongly influenced by agricultural practices, but little is known about the effects of fertilization and irrigation combination on ammonia oxidizers in agricultural soils. This study was designed to reveal how fertilizer type and irrigation frequency affect the ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities in a northern Chinese wheat-maize rotation soil.Materials and methodsSoil samples were collected from a long-term field experiment under different fertilization and irrigation regimes located in Wuqiao Experimental Station of China Agricultural University in June 2016. The abundance, diversity, and composition of AOA and AOB in the soils were investigated by using real-time PCR and Illumina Miseq sequencing approaches.Results and discussionThe abundance of AOA was higher in the irrigated treatments, but lower in the treatments without irrigation, than that of AOB. The AOA abundance was positively correlated with soil moisture, pH, and NO3−-N, while the AOB abundance was positively correlated with TN and NO3−-N. Soil potential nitrification activity (PNA) was significantly positively correlated with the AOB abundance. Both fertilizer type and irrigation frequency significantly affected Shannon, ACE, and Chao1 indices of the AOB community, while only irrigation frequency had a significant impact on Shannon index of the AOA community. PCoA analysis results indicated that irrigation frequency greatly affected the AOA community structure, while fertilizer type played a more important role in affecting the AOB community structure. Mantel test and correlation heatmap analysis results indicated that soil moisture, pH, and NH4+-N were significantly correlated to the AOA community structure, and TN and SOC were significantly correlated to the AOB community structure.ConclusionsThis study demonstrated that irrigation frequency greatly influenced the AOA community, while fertilizer type had a stronger effect on the AOB community. It was AOB but not AOA played a more important role in soil nitrification. Moreover, soil moisture, pH, and TN were the main determinants in driving the AOA community and TN and SOC were the main factors in influencing the AOB community.

Contrasting carbon and nitrogen rhizodeposition patterns of soya bean (Glycine max L.) and oat (Avena nuda L.): C and N rhizodeposition of soya bean and oat

H . Z a n g a,c , X . Q i a n a,d, Y . W e n e, Y . H u a, C . R e n b, Z . Z e n g a, L . G u o b & C . W a n g b aCollege of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China, bNational Oat Improvement Center of China, Baicheng Academy of Agricultural Sciences, Baicheng City 137000, China, cDepartment of Agricultural Soil Science, University of Goettingen, Goettingen 37077, Germany, dNational Engineering Laboratory of Wheat and Maize, Maize Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China, and eSchool of Environment, Natural Resources and Geography, Bangor University, Gwynedd LL57 2UW, UK

Variations of the nirS-, nirK-, and nosZ-denitrifying bacterial communities in a northern Chinese soil as affected by different long-term irrigation regimes

Denitrification causes nitrogen loss from agricultural soils and emission of nitrous oxide (N2O). Water addition leads to an increase in soil moisture which greatly influenced soil denitrification. However, it is unclear how irrigation management affected the denitrifying bacterial communities in agricultural systems. In the present study, we investigated the abundance, diversity, and composition of the nirS-, nirK-, and nosZ-denitrifying bacterial communities in the soil under different long-term irrigation regimes by using real-time PCR (qPCR) and Illumina MiSeq sequencing approaches. Results showed that the abundance of nosZ gene was 3.94–6.01 and 35.09–60.21 times more than that of nirS and nirK genes, and the abundance of nirS gene was 5.84–15.30 times higher than that of nirK gene, respectively, in different irrigation treatments. However, the Alpha diversity indices of the nirK-denitrifying bacterial community were higher than those of the nirS- and nosZ-denitrifying bacterial communities. Proteobacteria was the predominant phylum for all the denitrifying bacterial communities, and significant differences were observed in relative abundance of Alphaproteobacteria and Betaproteobacteria in predominant class between different irrigation treatments for the nirS- and nosZ-denitrifying bacterial communities, respectively. Irrigation significantly affected the abundance, Shannon and Invsimpson indices, and structure of the nirS- and nosZ-denitrifying bacterial communities, whereas it only minor influenced the structure of the nirK-denitrifying bacterial community. Furthermore, the shifts in abundance, diversity, and structure of the nirS- and nosZ-denitrifying bacterial communities correlated significantly with the soil property variations; however, no soil property was significantly correlated with the abundance and Alpha diversity index of the nirK-denitrifying bacterial community. Our results demonstrate that different long-term irrigation regimes greatly altered the abundance, diversity, and structure of the nirS- and nosZ- rather than the nirK-denitrifying bacterial communities.