• Authors:
    • Zhu, C.
    • He, K.
    • Pan, M.
    • Mao, G.
    • Pan, G.
    • Zheng, Y.
  • Source: Guizhou Agricultural Sciences
  • Issue: 1
  • Year: 2009
  • Summary: This study investigated the effects of different intercropping and interplanting patterns of green manure on soil fertility in Guizhou, China. The results showed that maize yield in improved soil fertility areas under 1:1 application ratio between organic and inorganic fertilizer averagely increased by 23.05% (102.5 kg/667m 2) compared with the conventional application pattern. The yields of the potato-green manure-maize pattern, rape-green manure-maize pattern and wheat-green manure-maize pattern increased by 51.2-66.0 kg/667m 2, 146.1 kg/667 m 2 and 146.7 kg/667 m 2, respectively compared with the conventional application pattern. The soil organic matter, total nitrogen, alkaline hydrolysis nitrogen, active P and active K content in improved soil fertility areas averagely increased by 0.23%, 0.033%, 23.23 mg/kg, 1.5 mg/kg and 17.75 mg/kg respectively and the soil fertility was increased to varying degrees. The high maize yield depends on its strong and high plants and better economic characters.
  • Authors:
    • He, J. -S.
    • Tan, K.
    • Rao, S.
    • Hu, H. F.
    • Ji, C. J.
    • Chen, A. P.
    • Tang, Y. H.
    • Smith, P.
    • Fang, J. Y.
    • Yang, Y. H.
  • Source: Global Change Biology
  • Volume: 15
  • Issue: 11
  • Year: 2009
  • Summary: Climate warming is likely inducing carbon loss from soils of northern ecosystems, but little evidence comes from large-scale observations. Here we used data from a repeated soil survey and remote sensing vegetation index to explore changes in soil organic carbon (SOC) stock on the Tibetan Plateau during the past two decades. Our results showed that SOC stock in the top 30 cm depth in alpine grasslands on the plateau amounted to 4.4 PgC (1 Pg = 10(15) g), with an overall average of 3.9 kg C m(-2). SOC changes during 1980s - 2004 were estimated at -0.6 g C m(-2) yr(-1), ranging from -36.5 to 35.8 g C m(-)2 yr(-1) at 95% confidence, indicating that SOC stock in the Tibetan alpine grasslands remained relatively stable over the sampling periods. Our findings are nonconsistent with previous reports of loss of soil C in grassland ecosystems due to the accelerated decomposition with warming. In the case of the alpine grasslands on the Tibetan Plateau studied here, we speculate that increased rates of decomposition as soils warmed during the last two decades may have been compensated by increased soil C inputs due to increased grass productivity. These results suggest that soil C stock in terrestrial ecosystems may respond differently to climate change depending on ecosystem type, regional climate pattern, and intensity of human disturbance.
  • Authors:
    • Grau, R.
    • Baptista, S.
    • Birkenholtz, T.
    • Lambin, E. F.
    • Ickowitz, A.
    • Hecht, S.
    • Geoghegan, J.
    • Lawrence, D.
    • DeFries, R. S.
    • Turner, B. L.
    • Uriarte ,M.
    • Schneider ,L.
    • Rudel, T. K.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 106
  • Issue: 49
  • Year: 2009
  • Summary: Does the intensification of agriculture reduce cultivated areas and, in so doing, spare some lands by concentrating production on other lands? Such sparing is important for many reasons, among them the enhanced abilities of released lands to sequester carbon and provide other environmental services. Difficulties measuring the extent of spared land make it impossible to investigate fully the hypothesized causal chain from agricultural intensification to declines in cultivated areas and then to increases in spared land. We analyze the historical circumstances in which rising yields have been accompanied by declines in cultivated areas, thereby leading to land-sparing. We use national-level United Nations Food and Agricultural Organization data on trends in cropland from 1970-2005, with particular emphasis on the 1990-2005 period, for 10 major crop types. Cropland has increased more slowly than population during this period, but paired increases in yields and declines in cropland occurred infrequently, both globally and nationally. Agricultural intensification was not generally accompanied by decline or stasis in cropland area at a national scale during this time period, except in countries with grain imports and conservation set-aside programs. Future projections of cropland abandonment and ensuing environmental services cannot be assumed without explicit policy intervention.
  • Authors:
    • Weischer, L.
    • Tan, X.
    • Heilmayr, R.
    • Seligsohn, D.
  • Year: 2009
  • Summary: from executive summary: "This report discusses the successes and challenges to effective regulation in China, outlining the major advances made in implementing effective energy efficiency programs in the past several years. These include targeted programs for both large and small enterprises, specific goals for government officials, and the development of energy statistics infrastructure. It also addresses U.S. competitiveness concerns in relation to the introduction of U.S. cap-and-trade policies, and specific opportunities for enhanced climate change cooperation between the two countries.
  • Authors:
    • Chang, X. X.
    • Yang, R.
    • Liu, W. J.
    • Su, Y. Z.
  • Source: Environmental Management
  • Volume: 43
  • Issue: 6
  • Year: 2009
  • Summary: Maintenance of soil organic carbon (SOC) is important for sustainable use of soil resources due to the multiple effects of SOC on soil nutrient status and soil structural stability. The objective of this study was to identify the changes in soil aggregate distribution and stability, SOC, and nitrogen (N) concentrations after cropland was converted to perennial alfalfa (Medicago sativa L. Algonguin) grassland for 6 years in the marginal oasis of the middle of Hexi Corridor region, northwest China. Significant changes in the size distribution of dry-sieving aggregates and water-stable aggregates, SOC, and N concentrations occurred after the conversion from crop to alfalfa. SOC and N stocks increased by 20.2% and 18.5%, respectively, and the estimated C and N sequestration rates were 0.4 Mg C ha-1 year-1 and 0.04 Mg N ha-1 year-1 following the conversion. The large aggregate (>5 mm) was the most abundant dry aggregate size fraction in both crop and alfalfa soils, and significant difference in the distribution of dry aggregates between the two land use types occurred only in the >5 mm aggregate fraction. The percentage of water-stable macroaggregates (>2, 2-0.25 mm) and aggregate stability (mean weight diameter of water-stable aggregates, WMWD) were significantly higher in alfalfa soils than in crop soils. There was a significant linear relationship between total SOC concentration and aggregate parameters (mean weight diameter) for alfalfa soils, indicating that aggregate stability was closely associated with increased SOC concentration following the conversion of crops to alfalfa. The SOC and N concentrations and the C/N ratio were greatest in the >2 mm water-stable aggregates and the smallest in the 0.25-0.05 mm aggregates in crop and alfalfa soils. For the same aggregate, SOC and N concentrations in aggregate fractions increased with increasing total SOC and N concentrations. The result showed that the conversion of annual crops to alfalfa in the marginal land with coarse-texture soils can significantly increase SOC and N stocks, and improve soil structure.
  • Authors:
    • Jia, L.
    • Raun, W. R.
    • Schroder, J.
    • Zhang, H.
    • Chen, X.
    • Li, R.
    • Cui, Z.
    • Zhang, F.
    • Miao, Y.
    • Li, F.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: Optical sensor-based N management strategies are promising approaches to improve N-use efficiency (NUE) and reduce environmental pollution risk. The objective of this study was to evaluate an active optical sensor-based in-season N management strategy for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). Initially, 10 field experiments were conducted at four villages in NCP in the 2004/05, 2005/06, and 2006/07 growing seasons to evaluate the in-season N requirement prediction developed by Oklahoma State University. Then the N application rates, winter wheat grain yield, NUE, economic returns, residual N content after harvest and apparent N loss were compared among three different management systems on a total of 16 farmer fields in 2005/2006 and 14 farmer fields in 2006/2007. The systems included a sensor-based system, a soil test-based approach crediting soil residual mineral N (N-min) to different depth at different growth stages, and common farmer practices. Averaged across site-years, the sensor-based, soil N-min-based N management strategies, and farmer practices produced similar grain yields but used 67, 88, and 372 kg N ha(-1), respectively. Nitrogen-use efficiencies were 61.3, 51.0, and 13.1% for the three methods of N recommendations, correspondingly. Their residual N content in the soil and apparent N loss were 115, 122, and 208 kg N ha(-1), and 4, 15, and 205 kg N ha(-1), respectively. The optical sensor-based N management strategy is relatively easy to use, has better potential to improve NUE and economic returns, and reduces residual soil N content and apparent N loss than other methods currently used in the NCP.
  • Authors:
    • Zhou, X.
    • Wu, F.
  • Source: Acta Pedologica Sinica
  • Volume: 46
  • Issue: 5
  • Year: 2009
  • Summary: Plenty of reports about effects of intercropping improving yield and reducing disease incidence are available, but little was reported about the mechanism of the effects. RAPD and T-RFLP methods were used to study effects of intercropping of cucumber with wheat, vicia villosa and clover, individually, on cucumber disease indexes, cucumber rhizosphere soil microbial community diversity and yield. Results showed that intercropping of cucumber with wheat and vicia villosa increased soil microbial community diversity in cucumber rhizosphere, and the effect of the latter was the most prominent. All intercropping modes increased cucumber yield significantly ( p
  • Authors:
    • Sun, J.
    • Chen, L.
    • Cheng, D.
    • Liu, Y.
    • Chen, J.
    • Zhou, H.
  • Source: Acta Phytophylacica Sinica
  • Volume: 36
  • Issue: 2
  • Year: 2009
  • Summary: To study the ecological effect of genetic diversity of wheat cultivars on Sitobion avenae, the population dynamics of S. avenae and its natural enemies was investigated in wheat fields. The spatial distribution of S. avenae was also analysed. Compared with monocultures, Beijing 837, the number of S. avenae apterae per 100 plants in intercropping patterns was significantly lower during the aphid peak period, and the cascade of population densities was: Beijing 837 monoculture (7422.0) > intercropped with KOK (5796.7) > intercropped with Hongmanghong (5406.7) > intercropped with Zhengzhou831 (5291.7) > intercropped with JP2 (4493.4) > intercropped with Zhongsiwumang (4155.0). The spatial distribution of S. avenae was changed from aggregated to uniform pattern. In the aphid parasitoid peak period, there were higher population densities of the aphid parasitoids in each intercropping field with a very significant level of P
  • Authors:
    • Yin, Q.
    • Jia, Z.
    • Xie, Y.
    • Guo, X.
  • Source: Jiangsu Journal of Agricultural Sciences
  • Volume: 25
  • Issue: 3
  • Year: 2009
  • Summary: Cultivation practices on fresh sweetpotato were conducted on both farmland and interplanting poplars field with three factors of cultivar, planting density and potassium fertilizer. It was different in composition of marketable root yield among three cultivars. Ningshu 192 was a kind of root-weight type cultivar which gave high ratio of marketable root yield. Ningzi 1 was a kind of root-number type cultivar which gave lots of small root. Jishu 18 was the intermediate which gave higher ratio of marketable root number following a better cultivation method. On farmland the high marketable root yield were harvested through planting density 1 hm 2 48 000 cuttings and more application of 225 kg/hm potassium sulfate fertilizer. The fresh sweetpotato production was unavailable on the interplanting poplars field due to very low marketable root yield.
  • Authors:
    • Xu, Z.
    • Cao, Z.
    • Chen, Y.
    • Liang, X.
    • Li, H.
    • Li, S.
  • Source: Journal of Soils and Sediments
  • Volume: 9
  • Issue: 5
  • Year: 2009
  • Summary: Background, aim, and scope - A large area of water eutrophication in the Tai Lake region of China was associated with nitrogen (N) and phosphorus (P) pollution, mainly due to the discharge of untreated rural wastewater (RW) into the surface water (SW) near villages of this region. A field experiment was conducted, using irrigation of RW plus urea fertilization under equal nitrogen (N) rate, namely, black water (BW), domestic wastewater (DW), gray water (GW), SW, and SW without any N application as a control (CK), to elucidate N removal by the paddy wetland system during the rice growing season of 2007. Materials and methods - SW, GW, DW, and BW were collected from the village of Liangzhu in subtropical China. Water samples were stored in darkness at 4°C in an icebox prior to analysis. Total nitrogen (TN) was analyzed by the spectrophotometric method with a continuous-flow automated analyzer. For the soil analyses, pH was measured using a pH meter with soil/distilled water=1:5; cation exchange capacity was determined with an unbuffered salt extraction method. Redox potential (Eh) was obtained using a pH meter with a platinum electrode, whereas organic carbon (C) was determined using the Walkley and Black method. TN was calculated by acid-alkali neutralization, after the soil samples were digested with concentrated sulfuric acid (H 2SO 4), distilled and then absorbed by diluted boric acid (H 3BO 3), and available N was determined by alkaline-proliferation law, after the samples were hydrolyzed, reduced, and absorbed by H 3BO 3. Available P was determined with the colorimetric method at the wave length of 660 nm, after the samples were extracted with NaHCO 3, and available K was extracted by unbuffered NH 4Cl and then determined by the atomic absorption spectrophotometer. The rice plant samples were digested with H 2SO 4-H 2O 2, and N contents were analyzed by the atomic absorption spectrophotometry. Results - Yield for the CK was significantly less ( P≤0.05) than those of SW, GW, DW, and BW, with the yield of BW significantly greater ( P≤0.05) than all the other treatments. The TN concentration of the floodwater in the paddy wetland system decreased rapidly after transplanting, rose significantly ( P≤0.05) after two N topdressings, and then decreased gradually as the following sequences: SW > GW > DW > BW > CK, but tended to be stable until 15 October. Meanwhile, TN removal rates from the wastewater were significantly higher ( P≤0.05) than those from the urea fertilizer. Total N load (TNL) increased significantly after two topdressings and reached the maximum value just after the first topdressing on 22 July: SW, 21.0 kg ha -1; GW, 19.1 kg ha -1; BW, 15.3 kg ha -1; DW, 14.3 kg ha -1; and CK, 0.57 kg ha -1. Subsequently, TNL declined gradually and reached stability on 15 October. Just after the rice seedlings were transplanted, the soil released a large amount of inorganic N (26.3%-40.4%); however, after the topdressing, the soil adsorbed a lot of N and TNL originating from the RW, which had decreased, ranging from 34.5% to 47.8%. Discussion - A reasonable N rate would be necessary for normal rice production in the Tai Lake region, which is different from those studies of other systems. Irrigation with RW for the paddy field could not only reduce the amount of commercial N fertilizer usage and irrigation water but also increase rice grain yield. Meanwhile, N use efficiency was improved by the combination of both N fertilizer and RW. The more N fertilizer was used, the higher the TN concentration in the flooded water would be, and the more potential risk of N to the surface water body. However, the N in RW could be removed more easily than that of the fertilizer by the paddy wetland system, which may be related to the existing form and concentration of N in the RW and urea fertilizer. The TNL in the floodwater had a positive correlation with the urea application rate, implying that appreciable amounts of N input might be lost, either by a heavy rainfall event or floodwater drainage using improper water management methods closely subsequent to the urea application. This revealed that using GW, DW, or BW instead of SW as irrigation water could decrease the loss of N applied and reduce the environmental pollution risk for the surface water. Conclusions - Supplemental N was necessary in this area for normal rice production, and the rice grain yield of CK (without any N fertilizer applied) was significantly lower than the other treatments; however, the yield of SW (with N fertilizer applied) was not significantly different from those of GW and DW. However, irrigation with RW in the paddy rice field could reduce costs of fertilizer and irrigation water. In addition, using BW would significantly increase rice yield revenues. The paddy wetland system also removed large quantities of N due to the irrigation with RW and applied N fertilizer, with the TN removal rates for RW significantly higher than that for the N fertilizer. Thus, application of RW instead of N fertilizer alone could greatly decrease the discharge of N into water bodies; thus, paddy wetland system can be considered as a new method for the RW treatment, especially in the Tai Lake region of China. Recommendations and perspectives - Based on this study, it would be strongly recommended to use RW irrigation after it had been disinfected for reducing part of commercial N fertilizer rate and saving some irrigation water in rice production with the paddy wetland system as a cost-effective way to remove the N from the RW and mitigate the non-point pollution. Future work should pay attention to the largest N-removal capacity of the paddy wetland system per unit and the effect on the rice grain quality irrigated with the RW.