• Authors:
    • Shi, X.
    • Luan, C.
    • Sui, P.
    • Chen, Y.
  • Source: Journal of Integrative Agriculture
  • Volume: 11
  • Issue: 6
  • Year: 2012
  • Summary: Weed control is one of the major constraint factors in crop production around the world. Field experiments were conducted during 2008-2009 under intercropping systems involving alfalfa ( Medicago sativa L.), sweet potato ( Ipomoea batatas [L.] Lam.), peanut ( Arachis hypogaea L.), and sunflower ( Helianthus annuus L.) in maize ( Zea mays L.) without any weeds control methods taken. The results demonstrate that maize||sunflower is most effective on weed suppression and that it also has a more competitively inhibitory effect on Xanthium compared with the other patterns by evaluating the Xanthium density and dry weight under different intercropping systems with maize. Maize||peanut, maize||alfalfa and maize||sweet potato intercrops have no apparent inhibitory effect on weeds. To further investigate the effect of maize||sunflower on weed control, indoor pot experiments were conducted by determining the effect of extractions on germination rate (GR), root vigor, MDA (malondialdehyde), SOD (superoxide dismutase) and POD (peroxidase) content of Xanthium. The results better prove that maize||sunflower extractions have more significant inhibitory effect on GR and young root vigor of Xanthium than maize monocrop extractions.
  • Authors:
    • Mu, C.
    • Li, X.
    • Xu, Q.
    • Liu, Z.
    • Zhang, J.
    • Gao, Z.
  • Source: Australian Journal of Crop Science
  • Volume: 6
  • Issue: 6
  • Year: 2012
  • Summary: This study examines the comparative effects of NaHCO 3 and Na 2CO 3 on young oat ( Avena sativa L.) plants to elucidate the species' physiological adaptive mechanisms to alkali stress. Factors considered are the intracellular influx and efflux of ions, ionic balance, osmotic adjustment, pH homeostasis, photosynthetic pigments and growth. Results show that, Na 2CO 3 had stronger effects than NaHCO 3, and that with increasing concentrations of both stresses the plant showed rising Na + influxes into the shoot resulting in Na + ion toxicity. This is tolerated by Na + sequestration in the vacuole; the accumulation mainly of Cl -, SO 42- and the synthesis of high concentrations of organic anions to maintain vacuolar ionic balance and, lastly by the synthesis of proline in the cytoplasm to avoid dehydration. Moreover, Na 2CO 3 stress inhibits growth more strongly, compared to NaHCO 3,because of the higher energy costs associated with Na + exclusion and compartmentalisation, the syntheses of organic anions, the syntheses of proline in the cytoplasm, reduced photosynthetic capacity and increased membrane permeability. Compared to the shoot, although the root had a similar response to both stresses, it showed a higher tolerance because high Na 2CO 3 stresses (>48 mmol L -1) resulted in significant increases in root tissue pH, but did not affect the pH homeostasis of the shoot. Additionally, while both stresses decreased root dry weight, they did not significantly affect root extension growth. This indicates that oat adopts an opportunistic guerrilla strategy by which it avoids resource-poor patches of soil (e.g. high alkali) while preferentially exploiting more favorable habitats by maintaining root extension.
  • Authors:
    • Liu, B.
    • Tian, J.
    • Yan, X.
    • Wang, H.
    • Liu, Q.
    • Peng, C.
  • Source: Journal of Biology
  • Volume: 29
  • Issue: 2
  • Year: 2012
  • Summary: The tribe triticeae represents a potential gene pool for improvement of crops such as wheat, rye and barley. Roegneria shandongensis is a tetraploid species widely distributing in the Eastern part of China. The species contains resistance to wheat yellow dwarf disease. However, the molecular markers used to investigate the genetic diversity of R. shandongensis were poorly studied. In this paper, a SSR-PCR system of R. shandongensis was optimized and tested. PCR system was optimized in five factors (Mg 2+, dNTP, primer, DNA template and Taq DNA polymerase) at five levels respectively. To discover the economic, rapid, and stable PCR system to screen SSR primers of R. shandongensis and detect the generality of the established system, one SSR primer Xgwm43-7B was used to screen the best PCR reaction system, and nine pairs of SSR primers (Xgwm18-1B, Xgwm32-3A, Xgwm6-4B, Xgwm60-7A, Xgwm67-5B, Xgwm77-3B, Xgwm88-6B, Xgwm95-2A and Xgwm99-1A) were used to test the generality. As a result, a satisfactory SSR-PCR reaction system for R. shandongensis with desirable repeatability and polymorphic bands was established. 20 L SSR-PCR system contained 1 * buffer, 2.875 mmol/L Mg 2+, 200 mol/L dNTP, 3 pmol primer, 45 ng template DNA, 1.5 U Taq polymerase, and ddH 2O then added up to terminal volume of 20 L. The generality test of PCR optimized system of R. shandongensis was carried out. The test result indicated that this system is also suitable for the amplification done by other SSR primers.
  • Authors:
    • Lu, Y.
    • Zeng, L.
    • Liang, G.
    • Tian, Y.
  • Source: Acta Phytophylacica Sinica
  • Volume: 39
  • Issue: 1
  • Year: 2012
  • Summary: In order to confirm the effect of pest control using intercropping with different crops, investigation was conducted to study the population dynamics of insect pests of maize and their natural enemies in the habitat of sweet corn monoculture or intercropping with other crops (mung bean, kidney bean, sweet potato or peanut) by the method of eyeballing. Damage by Asian corn borer (ACB), Ostrinia furnacalis (Guenee) between different habitats was also be analyzed and discussed. Results indicated that the amounts of two predator groups, spiders and ladybirds, increased in sweet corn intercropping habitats significantly. Individual number of spiders in the fields when sweet corn intercropped with mung bean and number of ladybirds in habitat of sweet corn intercropped with sweet potato were over 21% and 83% respectively more than that in sweet corn monoculture. The number of Trichogramma ostriniae Pang et Chen showed no significant difference between different habitats, with the parasitic rates of ACB eggs were over 86%. No significant differences was observed in number of ACB eggs, Spodoptera litura (Fabricius) or Rhopalosiphum maidis Fitch between sweet corn monoculture and intercropping habitats. However, the ACB damage rate in sweet corn intercropping habitats was less than that in sweet corn monoculture at harvest, with the least in sweet corn intercropped with mung bean habitat, in which the number of holes and larvae was decreased by 55.72% and 76. 70% respectively. Study suggested that sweet corn intercropping with other crops could be beneficial to conservation of natural enemies and control of insect pests in some extents.
  • Authors:
    • Cui, Z. L.
    • Zhang, F. S.
    • Chen, X. P.
    • Li, F.
    • Zhao, R. F.
    • Meng, Q. F.
    • Yue, S. C.
  • Source: AGRONOMY JOURNAL
  • Volume: 104
  • Issue: 2
  • Year: 2012
  • Summary: Investigating critical N concentration, that is, the minimum N concentration necessary to achieve maximum growth, provides insights into N nutrition and can serve as a guide to improving agricultural practices and regulations. Our objectives were to evaluate N dilution curves for deficient, optimal, and excess added N and to determine the critical N dilution curve for winter wheat ( Triticum aestivum L.) in the North China Plain (NCP) based on 15 N fertilization experiments with three to six N fertilization rates. The N supplements significantly affected the N dilution curve, and increased N supply generally resulted in a greater N concentration. The critical N dilution curve for winter wheat was described by the equation nitrogen concentration (N c)=4.15 W -0.38 when aboveground biomass was between 1 and 10 Mg dry matter (DM) ha -1. When aboveground biomass was <1 Mg DM ha -1, the constant critical value N c=4.15% DM, which was independent of aboveground biomass. This curve was lower than that of winter wheat in France. This critical N dilution curve was validated through the nitrogen nutrition index (NNI) defined as the ratio between measured N concentration and critical N c. The critical N dilution curve holds promise as an efficient tool for guiding N-fertilization practices and regulations for winter wheat production in the NCP.
  • Authors:
    • Luo, J. F.
    • Ding, W. X.
    • Cai, Y. J.
  • Source: GEODERMA
  • Volume: 181
  • Year: 2012
  • Summary: There is a high spatial variation in N2O emission from agricultural fields and N2O emissions from fields cultivated with stalk-crops was generally measured in the interrow area. The aim of this study was to evaluate the difference in seasonal N2O emissions between interrow soil and interrow + row soil, and to understand the effect of different fertilizers on N2O emissions in a maize-cultivated sandy loam soil in the North China Plain. The experiment included five treatments: organic manure (OM), half-organic manure N plus half fertilizer N (HOM), fertilizer NPK (NPK), fertilizer NK (NK) and control (CK). Cumulative N2O emission from interrow + row soil during the maize growth season was 0.84-122 kg N ha(-1) with an average of 0.98 kg N ha(-1) in the N-fertilized treatments, significantly higher than the 0.30-0.49 kg N ha(-1) from interrow soil. However, no significant difference was observed in the CK treatment. The measurement in interrow soil underestimated N2O emissions by 44-67%. This difference mainly occurred at the two peak emission periods following fertilizer application probably due to discrepancy in soil denitrification potential. Manure application more efficiently increased difference in N2O emission between interrow soil and interrow + row soil than inorganic N fertilizer application. The higher NO concentration did not induce larger N2O emission from interrow soil in the NK treatment than in the NPK treatment, but did from interrow + row soil, resulting in greater difference in N2O emission between interrow soil and interrow + row soil. It is suggested that measuring N2O emission solely from interrow soil could underestimate seasonal N2O emissions, and partly mask the effect of N fertilizer application rates on N2O emission in a maize-cultivated soil in the North China Plain.
  • Authors:
    • Fang, C.
    • Ye, Z.
    • Chen, X.
    • Wang, L.
    • Li, Z.
    • Liu, C.
    • Cui, J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 123
  • Year: 2012
  • Summary: Dynamics of reclaimed coastal wetland soils under cultivation has not been well understood, especially at temporal scales longer than a century. In this study, we analyzed major chemical properties of plow-layer soils extensively sampled under two cropping systems (paddy rice vs. upland cropping) along a 500-year soil chronosequence created by intermittent reclamation of coastal salt marshes. The results suggested a rapid desalinization of soil immediately after reclamation. During 500 years of cultivation, the decalcification process lowered soil pH from >8 to nearly neutral. Soil organic carbon (SOC) contents markedly declined in the initial 16 years, but then rapidly recovered within 30 years and thereafter slowly accumulated with cultivation duration. Meanwhile, the recalcitrance of SOC increased. Soil nutrient status was enhanced after centuries of cultivation as indicated by the improved total nitrogen (TN) and phosphorous (TP). Amorphous Fe oxyhydrates progressively decreased, but the crystallinity of Fe oxyhydrates increased with cultivation time. Cropping system greatly affected plow-layer soil properties, with paddy soils having higher SOC, MBC, NH 4OAc-extractable Ca 2+, but lower TP, NH 4OAc-extractable K +, potentially mineralizable nitrogen and Fe crystallinity than upland soils. Most soil properties revealed clear temporal patterns with more remarkable changes occurring in the first several decades after reclamation than in the following centuries. In conclusion, there was a transition phase of the soil system within the first several decades after reclamation of coastal wetlands, possibly harmful to agricultural production, but centuries of cultivation seemed to have significantly improved overall soil fertility. © 2012 Elsevier B.V..
  • Authors:
    • Chan, A.
    • He, Y. Q.
    • Peng, Y.
    • Zhou, J.
    • Cui, J.
  • Source: PLANT AND SOIL
  • Volume: 359
  • Issue: 1-2
  • Year: 2012
  • Summary: Biological processes in agro-ecosystems have been affected by atmospheric nitrogen (N) deposition, but there is uncertain of the N deposition fluxes and associated variations. This study aimed to characterize the atmospheric inorganic N (AIN) in wet deposition to a typical red soil farmland at the Red Soil Ecological Experiment Station, Chinese Academy of Sciences in Southeast China. We collected rain samples using an ASP-2 sampler at a 4-week interval, recorded rainfall and rain frequency by an auto-meteorological experiment sub-station and determined NO (3) (-) - and NH (4) (+) -N levels in precipitation with an AutoAnalyzer 3 for five continuous years (2005-2009). Precipitation-weighted concentrations of NO (3) (-) - and NH (4) (+) -N ranged from 0.02 to 0.17 mg L-1 month(-1) N and 0.05 to 0.42 mg L-1 month(-1) N, respectively. Wet AIN deposition fluxes substantially varied with season. The highest AIN level was found in spring (March to May) with the average of 11.3 kg ha(-1) season(-1) N, which was significantly higher than that in autumn and winter (p < 0.01). Annual AIN fluxes ranged from 26.4 to 39.0 kg ha(-1) a(-1) N, which approached to the critical loads. The NH (4) (+) -N deposition fluxes varied from 17.4 to 27.0 kg ha(-1) a(-1) N, accounting for 65.8-71.5% of annual AIN deposition fluxes, whereas the AIN fluxes in the rainy season (April to June) ranged from 5.0 to 20.2 kg ha(-1) a(-1) N, accounting for 17.6-51.9% of annual AIN deposition fluxes. Wet inorganic N deposition has intensively been influenced by human activities, particularly agricultural activities, and would increase potential ecological risk in the red soil agricultural ecosystem. Our results suggest that wet N deposition to red soil farmlands, particularly in the rainy season should not be neglected.
  • Authors:
    • Li, N.
    • Li, L.
    • Qiao, Y.
    • Liang, Y.
    • Han, X.
    • Ding, X.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 122
  • Year: 2012
  • Summary: It is still unclear that whether substantial amounts of organic manure amendment could increase soil organic carbon (SOC) sequestration in a Chinese Mollisol with relatively high organic C content. Further, changes accompanied by different organic carbon (C) fractions are not well understood based on long-term experiment. The knowledge of this kind is important for assessing the potential for C sequestration of a high SOC soil and selecting effective management practices for increasing soil C sequestration and productivity in agroecosystem of northeastern China. This study was aimed to assess the effects of 10 years' organic manuring at various rates combined with chemical fertilizer on organic C sequestration in topsoil (0-20cm) and to identify changes in different SOC (total, labile, and recalcitrant) pools. Five fertilization treatments were included: (1) CK, unfertilized control; (2) OM 0, only chemical fertilizer, no manure added; (3) OM 1, organic manure added at 7.5Mgha -1 year -1 plus chemical fertilizer; (4) OM 2, organic manure added at 15Mgha -1year -1 plus chemical fertilizer; and (5) OM 3, organic manure added at 22.5Mgha -1year -1 plus chemical fertilizer. Chemical fertilizer was supplied with the same rate in each fertilized treatment. We found that the application of graded rates of manure from OM 1 to OM 3 significantly enhanced total SOC, labile C pools, and recalcitrant C pool as compared with OM 0 and CK. The C storage (in top 20cm) in the OM 0, OM 1, OM 2, and OM 3 was increased by 3.19%, 12.5%, 14.5%, and 18.2%, respectively, over the CK treatment, suggesting that the chemical fertilizer addition had less effects on C-sequestration in topsoil compared to manure plus mineral fertilizer amendment. Moreover, topsoil C-sequestration increased with organic manure addition rates with an order of OM 3 (10.5Mgha -1)>OM 2 (8.4Mgha -1)>OM 1 (7.2Mgha -1). A positive relationship between C sequestration and organic manure input indicates that the soil has not reached its maximum capacity of C sequestration. Application of organic manure with chemical fertilizer was found to produce greater size of both labile and recalcitrant pools than application of mineral fertilizers alone. In most cases, the increases in these C fractions were greater when organic manure was supplied at higher rates. Moreover, increase in recalcitrant C (10.5-29.5%) was significantly higher than labile C (5.6-10.2%) in manure treated plots as compared with no amendment plot. This indicated that a majority of organic C sequestered due to C inputs was accumulated and stabilized in recalcitrant C pool. In general, organic manure combined with inorganic fertilizer exerted greater influence on topsoil C storage and crop yield than chemical fertilizer alone. Based on crop yield and soil C storage, applying organic manure at the rate of 22.5Mgha -1year -1 was the most effective way to improve soil productivity and C sequestration in the agroecosystem of northeastern China. However, taking use efficiency of organic inputs and environmental factors into consideration, application of manure at moderate rate (about 15Mgha -1year -1) may be more feasible in this region. © 2012 Elsevier B.V.
  • Authors:
    • You, X.
    • Duan, Q. Wei
    • An, R.
    • Ge, Z. W.
    • Gong, J. R.
    • Huang, Y. M.
  • Source: PLANT AND SOIL
  • Volume: 360
  • Issue: 1-2
  • Year: 2012
  • Summary: This study aims to test the effects of forest age on soil respiration in poplar ecosystems in northern China and to separate the contributions of root respiration (Rr) and soil microbes to the total soil respiration (Rs). Rs in three poplar forests (5, 10, and 15 years old) were measured using an LI-6400-09 soil chamber connected to an LI-6400 portable infrared gas analyzer during the growing seasons in 2007 and 2008. Root respiration was measured using the root excision method. The soil micro-organisms were quantified using the dilution-plate method. The results show that Rs was the highest in the 5-year-old forest and lowest in 15-year-old forest. The contribution of Rr to Rs ranged from 29.4 to 81.0%. Rr/Rs tended to be significantly higher in the 15-year-old forest than that in the younger forests; but Rr was the highest in the 5-year-old forest. Temporal variation in Rs can be largely accounted by fine-root biomass (R = 0.718), while soil N was significantly negatively correlated with Rs (R = -0.646). Rs, Rr and Rr/Rs vary significantly with the forest age. The lower Rs in the older forests increased their carbon use efficiency. Underground factors, dominated by fine-root biomass, affect Rs, Rr and Rr/Rs substantially. Soil microbial community structure is a particularly important underground factor.