• Authors:
    • Sathaye, J. A.
    • Makundi, W. R.
  • Source: Environment, Development and Sustainability
  • Volume: 6
  • Issue: 1-2
  • Year: 2004
  • Summary: This paper summarizes studies of carbon mitigation potential (MP) and costs of forestry options in seven developing countries with a focus on the role of agroforestry. A common methodological approach known as comprehensive mitigation assessment process (COMAP) was used in each study to estimate the potential and costs between 2000 and 2030. The approach requires the projection of baseline and mitigation land-use scenarios derived from the demand for forest products and forestland for other uses such as agriculture and pasture. By using data on estimated carbon sequestration, emission avoidance, costs and benefits, the model enables one to estimate cost effectiveness indicators based on monetary benefit per tC, as well as estimates of total mitigation costs and potential when the activities are implemented at equilibrium level. The results show that about half the MP of 6.9 GtC (an average of 223 MtC per year) between 2000 and 2030 in the seven countries could be achieved at a negative cost, and the other half at costs not exceeding $100 per tC. Negative cost indicates that non-carbon revenue is sufficient to offset direct costs of about half of the options. The agroforestry options analyzed bear a significant proportion of the potential at medium to low cost per tC when compared to other options. The role of agroforestry in these countries varied between 6% and 21% of the MP, though the options are much more cost effective than most due to the low wage or opportunity cost of rural labor. Agroforestry options are attractive due to the large number of people and potential area currently engaged in agriculture, but they pose unique challenges for carbon and cost accounting due to the dispersed nature of agricultural activities in the tropics, as well as specific difficulties arising from requirements for monitoring, verification, leakage assessment and the establishment of credible baselines.
  • Authors:
    • Shi, Y.
    • Jjemba, P. K.
    • Song, Q.
    • Li, F.
  • Source: Soil Biology and Biochemistry
  • Volume: 36
  • Issue: 11
  • Year: 2004
  • Summary: Microbial biomass C (MBC) is one of the soil properties used as an indicator for the fertility status of a soil. A study was conducted on a semi-arid Loess Plateau in China. The field was planted with spring wheat and mulched with plastic film for various lengths of time. Our primary objectives were to (i) explore the influence of film mulching on soil MBC and soil fertility, and (ii) seek an effective approach of maintaining and improving sustainability of cropland mulched with plastic film in two growing seasons. Four treatments were tested, non-mulching (M0), mulching for 30 days after sowing (M30), mulching for 60 DAS (M60) and mulching for the whole growing period (Mw). An increasing air temperature with time within the growing season promoted soil MBC in the two growing seasons, but a severe drought led to a lower MBC in 2000 compared with the wet year of 1999. Film mulching promoted MBC significantly in the 2 years, but decreased soil organic carbon (SOC). SOC is very low in the experimental soil, accounting for the higher MBC/SOC ratio compared with ratios reported by others. The SOC is greatly reduced in the non-mulched and the Mw treatments compared to the M30 and M60 treatments. In conclusion, the benefits of film mulching in semi-arid agricultural systems are enormous but realizing their full potential depends on how long the mulching material is maintained during the growing season. In the system tested, it is desirable to mulch the plots for 30–60 DAS in order to enhance microbial biomass and cycling of nutrients and also to provide a more stable soil micro-environment that generates more residues in the rhizosphere.
  • Authors:
    • Liu HongBin
    • Li ZhiHong
    • Zhang YunGui
    • Zhang WeiLi
    • Lin Bao
  • Source: Scientia Agricultura Sinica
  • Volume: 37
  • Issue: 5
  • Year: 2004
  • Summary: A study was conducted in Beijing, China to determine the nitrate content in 254 soil profiles under different land use types, using global positioning systems and deep soil core sampling, for the forecasting of the potential of nitrate pollution in groundwater . NO 3--N accumulation in 0-400 cm soil profiles in protected vegetable fields was the highest (1230 kg/ha) while it was lowest (69 kg/ha) in paddy fields. Even for the same land use types, NO 3- accumulation among sampling fields differed significantly. The percentage of soil profiles with NO 3--N accumulation more than 800 kg/ha was 70.4, 50.0 and 33.3 in protected vegetable field, orchards and open vegetable fields, respectively, while it was only 8.6 and 125 in winter wheat-summer maize rotation fields and spring maize fields, respectively. NO 3--N content reduced sharply with the depth of the soil profile in dryland fields. Although there was no remarkable difference in the ratio of NO 3--N content in 200-400 cm soil layer to the whole profile among various land use types, NO 3--N accumulation rates differed distinctly. The highest was protected vegetable fields and orchards while the lowest was observed in winter wheat-summer maize rotation fields and spring maize fields. The results indicate that protected vegetable fields pose a serious threat to groundwater pollution while cereal fields have lesser risks.
  • Authors:
    • Pu, X. P.
    • Kang, M. Y.
    • Hu, Z. Z.
    • Long, R. J.
    • Dong, S. K.
  • Source: Grass and Forage Science
  • Volume: 58
  • Issue: 3
  • Year: 2003
  • Summary: Abstract The productivity and nutritive value of some cultivated perennial grasses, Bromus inermis (B), Elymus sibricus (S), E. nutans (N), Agropyron cristatum (A), Poa crymophila (P) and mixtures B + N, S + A, B + S + A, S + B + N, N + S + A, B + S + N + A, B + N + A + P, B + S +A + P and S + N + A + P, in the alpine region of the Tibetan Plateau were investigated. Elymus nutans and E. sibricus and the mixtures, B + S + N + A, B + S +A + P and S + N + A + P, were most productive with yields of dry matter (DM) of between 11 000 and 14 000 kg-1 of biomass annually in the second harvest year. Acid-detergent fibre (ADF) concentrations increased (P < 0·05), and crude protein (CP) concentrations and in sacco DM degradability values decreased (P < 0·05) with the maturity of the cultivated grasses. Swards, based on these species and mixtures, have the potential to be the main choices for cultivation in the Tibetan Plateau because they produce more nutrients than other grass species and mixtures. Late August (flowering stage of dominant grasses) is the optimum time for harvesting as the yield of rumen-degradable CP is highest that of DM relatively high and the DM degradability is satisfactory.
  • Authors:
    • Yang, H.
    • Walters, D. T.
    • Dobermann, A.
    • Cassman, K. G.
  • Source: Annual Review of Environment and Resources
  • Volume: 28
  • Issue: 1
  • Year: 2003
  • Summary: Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.
  • Authors:
    • Huang, D. L.
    • Dai, Z. Y.
    • Liang, G. W.
    • Pang, X. F.
    • Yang, Y. Z.
  • Source: Journal of Yangzhou University, Agricultural and Life Sciences Edition Issue: 2
  • Volume: 24
  • Issue: 2
  • Year: 2003
  • Summary: The development of cotton bollworm (H. armigera) fed with different host foods was investigated. Higher values for pupal weight and eggs per female were recorded for the cotton bollworms fed with pea and soyabean leaves, compared with those fed with aubergine fruit and groundnut leaf. The rate larval development was highest with pea leaf, followed by maize fruits, and lowest for cotton leaf, flower, bud and boll. Based on values of the index of population trend, the preference of the cotton bollworm to different host foods were as follows: pea > soyabean > maize > Chinese sorghum > cotton > groundnut > aubergine. The results of a study of the dynamics of the cotton bollworm population in a cotton field in China are presented.
  • Authors:
    • Zhou, R. L.
    • Zhang, T. H.
    • Zhao, H. L.
  • Source: Acta Pedologica Sinica
  • Volume: 40
  • Issue: 2
  • Year: 2003
  • Summary: Results are presented of a field experiment conducted on soil environment and productivity formation process of maize in 5 major types of farmlands of Horqin, Nei Menggu, China. The 5 main types of cropland are irrigated sandy loam, irrigated loam sandy soil, dry slope land of sandy loam, dryland of sandy loam, and dryland of sandy soil. The average soil water content, soil temperature, integrated index of soil nutrients, and height and biomass of maize are determined. The correlation coefficients between biomass and soil indexes, in terms of N, P, K, soil moisture and soil organic matter are also determined.
  • Authors:
    • Beghin, J. C.
    • Fang, C.
  • Source: Agricultural trade and policy in China: issues, analysis and implications
  • Year: 2003
  • Summary: This chapter assesses the protection and comparative advantage of China's major agricultural crops in six regions, using a modified Policy Analysis Matrix and 1997-2000 data. The following commodities are considered: early indica rice, late indica rice, japonica rice, wheat, maize, sorghum, soyabean, rapeseed, cotton, tobacco, sugarcane, and a subset of fruits and vegetables. The results suggest that, with the exception of high quality rice, the production of grains and oilseeds tends to suffer from a lack of comparative advantage over other crops in China, such as fruit and vegetables, tobacco and cotton. Further, it is concluded that grain self-sufficiency policies reduce allocative efficiency several-fold.
  • Authors:
    • Rozelle, S.
    • Hu, R.
    • Huang, J.
    • Pray, C. E.
  • Source: The Plant Journal
  • Volume: 31
  • Issue: 4
  • Year: 2002
  • Summary: Bt cotton is spreading very rapidly in China, in response to demand from farmers for technology that will reduce both the cost of pesticide applications and exposure to pesticides, and will free up time for other tasks. Based on surveys of hundreds of farmers in the Yellow River cotton-growing region in northern China in 1999, 2000 and 2001, over 4 million smallholders have been able to increase yield per hectare, and reduce pesticide costs, time spent spraying dangerous pesticides, and illnesses due to pesticide poisoning. The expansion of this cost-saving technology is increasing the supply of cotton and pushing down the price, but prices are still sufficiently high for adopters of Bt cotton to make substantial gains in net income.
  • Authors:
    • Li, X. Y.
    • Zhao, H. L.
    • Gao, C. Y.
    • Li, F. R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 91
  • Issue: 1-3
  • Year: 2002
  • Summary: Winter wheat (Triticum aestivum L.) monoculture is common in wheat-growing areas of the Loess Plateau of northwest China. This system is characterized by nearly 3-month summer fallow from wheat harvest at the end of June or early July to sowing in late September. It not only lowers the overall precipitation-use efficiency because of the large amount of evaporation from the bare soil surface during the fallow period but also entails high risk of erosion by summer rainstorms. There is a need to develop more effective cropping systems to replace the current production system. Seven alternative rotations, mainly using wheat, rapeseed, corn, potato, pearl millet, linseed, alfalfa and sweetclover, were established and their use of environmental resources, production performance, energy efficiency, soil fertility sustainability, and soil conservation effectiveness were compared with continuous wheat cropping. The rotations had greater potential use of environmental resources. Despite showing no clear advantage in grain yields, all rotations were significantly higher in total above-ground biomass production and more efficient in energy transformation compared with continuous wheat cropping. After a 3-year cycle, the rotations did not adversely affect soil bulk density but some rotations significantly increased soil water-stable aggregates compared with the initial measurement. For the rotations based on the inclusion of legumes, the availability of N was apparently improved but the total P was substantially reduced compared with the initial measurement and continuous wheat cropping. An assessment of soil conservation effectiveness with a weighted soil conservation effectiveness index (WSCEI) indicated that the rotations performed much better than continuous wheat cropping in conserving soil and water resources. This study also strongly recommend that it is feasible to cultivate winter wheat followed by a 3-month legume fallow crop in year I and then a summer crop cultivation in the next. This system provides a soil cover during both erosion-prone rainy periods while leaving the soil bare for about 7 months (October-April) every 2 years. Another alternative is to cultivate winter wheat followed by a 15-month legume crop cultivation in years I and 2 and then a summer crop in year 3. This system allows the soil to be covered during three rainy periods while leaving the soil bare for about 7 months every 3 years. As most of this 7-month period is winter with low rainfall (snow) and temperatures below 0degreesC, not only is soil evaporation very low but the risk of erosion is also low. (C) 2002 Elsevier Science B.V. All rights reserved.