退耕还林(草)背景下黄土高塬沟壑区长武县粮食潜力及安全分析

鉴于黄土高塬沟壑区退耕还林(草)工程和林果业迅速发展所带来的粮食-人口-资源矛盾问题,收集农业气象、耕地等数据,基于GIS技术,采用机制法分析了退耕还林(草)工程实施前后的1993年和2009年黄土高塬沟壑区长武县粮食潜力和安全问题,明确了气候要素限制下长武县各层次粮食生产潜力及开发程度。长武县1993年到2009年可实现粮食潜力总量下降了7.8%,而实际粮食生产总量增产了4.0%,潜力实现率由61.58%增至68.59%。17a间,主要粮食作物播种面积减少了27.8%,单产平均提高44.1%,而人口增长了12.5%,人均播种面积下降了35.9%,人均粮食产量由320.1kg减少至296.0kg,下降了7.5%。温度和土地有效系数的提高是促进可实现粮食潜力增加的主要因素,耕地减少是限制粮食增幅的直接原因,单产提高是促进增产的主要因素。耕地减少、人口增加是该区粮食安全的核心问题,粮食单产的提高是维持该区粮食安全稳定的保障。针对该区粮食安全问题的严峻性,提出必须以全面提高粮食单产为目标,科学增加辅助能量投入,推进基本农田建设,大力推广耕地保育技术和持续高效现代农业。     

SOIL ATTRIBUTES AFTER THE CONVERSION FROM FOREST TO PASTURE IN AMAZON

The conversion from forest to grassland is drastically changing soil characteristics in Amazon, leading to land degradation when it is poorly managed. Chemical and physical changes of a Typic Hapludox were evaluated as a function of the conversion (by means of fire) from forest to Brachiaria brizantha cultivation. Samples from the remaining forest were also sampled. Treatments were made to pastures eight (P8), thirteen (P13) and fifteen (P15) years after conversion, and to land under continuous grazing, and to a remaining forest area (control). The forest soil was more acidic than the pasture soils. Soil density and Ca⁺² increased after the conversion, regardless of the period of grazing. Carbon stocks varied from 31·2 t ha⁻¹ in the forest soil to 37·4 (P8), 33·5 (P13) and 30·7 t ha⁻¹ (P15). Copyright © 2011 John Wiley & Sons, Ltd.     

A computerized soil information system for arable land in Japan

A computerized soil information system was compared to manual punch card methods for storage and retrieval of Japanese soil survey data. In spite of the high cost, a soil information system using computers is the most appropriate system for the future, because by this method more than three factors can be analyzed simultaneously, various kinds of soil map data can be stored, retrieved and updated and many kinds of interpretative maps can be constructed automatically. There are large amounts of valuable soil survey data available in Japan which previously were used only for drawing soil maps. These should be utilized to develop a computerized soil information system. At the end of this report, essential processes and the possible structure of a Japanese Soil Information System were discussed.     

Root phosphatase activity of sorghum genotypes grown with organic and inorganic sources of phosphorus 1

Abstract

Relatively insoluble sources of phosphorus (P) may require solubilization, and organic P (P_o) may require hydrolysis to inorganic P (P_i) before P can be readily absorbed by plants roots. The mechanisms for these processes, however, are unknown. Root phosphatase (Pase) activity was measured to assess its relationships to P uptake by seven sorghum [Sorghum bicolor (L.) Moench] genotypes grown with P_o (ethylammonium phosphate, glycerophosphate, and phenylphosphate) and P_i (KH₂PO₄, calcium tribasic phosphate, calcium pyrophosphate, aluminum phosphate, and ferric phosphate) in nutrient solutions in a greenhouse.

Plants grown with P_o had lower root Pase activities than plants grown with P_i NB9040 and SC369–3–1JB (tolerant to low levels of P) had lower root Pase activities than CK60‐Korgi and SC33–9–8‐E4 (sensitive to low levels of P), with the other genotypes having intermediate root Pase activities. Higher root Pase activity was associated with lower root P concentrations, but Pase activity was not related to dry matter yield of roots. In experiments where genotypes were grown three weeks with KH₂PO₄ before being transferred to other sources of P, within four days root Pase activity patterns were similar to those for plants grown initially in the particular P_o or P_i compound. Root Pase activity of sorghum plants appeared to be an indicator of P status or P deficiency stress in the plants, and not associated with making P_o or P_i compounds more available for plant use.     

Influence of organic mulching and nitrogen application on essential oil yield and nitrogen use efficiency of rosemary (Rosmarinus officinalis L.)

In a field study conducted at Bangalore, India for two years (2003–2004 and 2004–2005), eight treatment combinations consisting of two variables, organic mulch (lemongrass spent material as mulch at 7.5 t ha^?1 and no mulch) and four levels of nitrogen fertilizer (0, 100, 200 and 300 kg ha^?1) were examined to observe the effect of organic mulching on nitrogen use-efficiency, and herb and essential oil yield in a multiharvested rosemary crop. The results revealed that application of lemongrass spent material as mulch increased the herb and essential oil yields in rosemary by 16.2 and 24.2%, respectively, over the non-mulched control at first harvest. Corresponding values for the regenerated crop harvest were 18.8 and 16.8%. A significant response to N was observed with 300 kg N ha^?1 in non-mulched plots compared with 200 kg N ha^?1 in mulched plots. Using lemongrass spent material as mulch, nitrogen uptake by the rosemary crop increased by 15.1% over the non-mulched control. At 200 kg N ha^?1, apparent recoveries by the crop were estimated to be 33.64% for the non-mulched control, and 37.79% with mulch. The quality of the rosemary essential oil, in terms of the concentrations of its major constituents, α-pinene, 1 : 8 cineole, camphor and verbenone, was not affected by the use of organic mulching and nitrogen fertilization, and these constituents were found to be of astandard acceptable in international trade.     

Phosphorus–microbes interaction on growth,yield and phosphorus-use efficiency of irrigated cotton

The phosphorus-use efficiency of crops in high pH soil is low. A randomized complete block design in a 3 × 2 split-plot experiment was conducted on a high pH silt loam (Typic Ustochrepts) to evaluate whether P-solubilizing microbial (PSM) inocula were able to improve the P fertilization effects on irrigated cotton (Gossypium hirsutum L., cultivar CIM-482). Cotton was planted after seed treatment with PSM inoculation at 0, 22 and 44 kg P ha^?1. Results showed that soil microbial populations were significantly higher throughout the cotton-growing season in response to P fertilization and PSM inoculation. Both P fertilization and PSM inocula exerted a significant effect on cotton biomass and Puptake without an interaction. Economic analyses suggest that PSM inocula alone significantly increased P-use efficiency (8%), reduced cost and improved net income (by $36 ha^?1) of irrigated cotton production. Moreover, the relationship between relative yield and P fertilization with PSM inocula showed that 95% of the maximum yield of cotton was produced at 22 kg P ha^?1, whereas in the absence of PSM inocula, 95% relative yield was obtained at 36 kg P ha^?1, asaving of ～39% applied P with PSM inoculation.     

Effects of deficit irrigation on tomato and eggplant and their infection with the root-knot nematode under controlled environmental conditions

Deficit irrigation has been widely investigated as a valuable strategy for dry regions where water is the limiting factor in crop cultivation. Soil moisture can be one of the important factors that influence root-knot nematode (RKN) disease development. To determine how different levels of irrigation can affect disease development, irrigation regimes ranging from 20% to full field capacity (FC) were applied to tomato and eggplant plants inoculated with Meloidogyne javanica (M. javanica) under controlled conditions. In addition, in vitro bioassays were done to evaluate the effect of water potential and soil moisture content on M. javanica viability in the soil and reproduction on plant hosts. The relative egg hatching percentage decreased significantly with decreasing water potential from –0.1 to –1 MPa. The use of 80% irrigation level caused minor reductions in growth but significantly reduced nematode infection load. Nematode infection was reduced even further at lower levels of irrigation, however this also led to marked reductions in fresh and dry weights of the tomato and eggplants. Therefore, deficit irrigation could be used at a rate of 80% or 60% of FC to increase water use efficiency and reduce the level of RKN (M. javanica) infection without greatly reducing the growth performance of tomato and eggplant crops.     

Quantification of loss in oilseed rape yield caused by delayed sowing date in a Mediterranean environment

ABSTRACT

Rapeseed acreage has been increasing fast in the last few decades and cultivated areas have expanded into lower latitudes because of the high value of its seed. This work evaluates the effect of date of sowing and nitrogen (N) fertilization on crop productivity and N use efficiency in a Mediterranean environment. The experiment was arranged in a split-plot design with the dates of sowing as the main-plots and N rates the sub-plots. Rapeseed recovered 128 to 212 kg N hm^-2 before top-dress N application in late winter if sown before the last week of September. Seed yield was very dependent on the date of sowing, varying from 3.4 to 6.2 Mg hm^-2 on the first sowing date in September to 0.3 to 1.0 Mg hm^-2 on the last sowing date in November. The daily loss in seed production was 68.9 kg hm^-2 (or 482.3 kg hm^-2 per week) or 1.53 % (or 10.7 % per week). N rate significantly increased seed yield within each sowing date but did not allow late-sowed plants to regain the productivity levels of those sown earlier. Apparent N recovery and agronomic N efficiency were particularly dependent on the growing conditions associated to different sowing dates.     

干旱胁迫对水土保持先锋植物类芦光合特性的影响

以水土保持先锋植物类芦为研究材料,通过4个不同梯度干旱胁迫的盆栽试验,测定类芦的光合色素、叶绿素荧光参数和光合参数.研究干旱胁迫对类芦的光台特性的影响.结果表明:中度、轻度干旱胁迫类芦叶绿素含量增加,叶绿素a/b比值下降,干旱胁迫下叶绿素荧光参数F0、Fm,Fv提高,Fv/Fm、Fv/F0下降.类芦叶片的胞问CO2浓度随千旱程度加重而逐渐增加,日变化表现为上午缓慢上升,下午快速上升,到16:00达到最高.净光合速率、气孔导度、蒸腾速率日变化均表现为单峰型,为先升后降,12:00达到高峰,日均值随着干旱程度加重而逐渐下降.中度、轻度干旱胁迫下WUE提高,重度干旱WUE稍有下降,类芦具有较强的耐干旱能力.     

Drought and ecosystem carbon cycling

Drought as an intermittent disturbance of the water cycle interacts with the carbon cycle differently than the ‘gradual’ climate change. During drought plants respond physiologically and structurally to prevent excessive water loss according to species-specific water use strategies. This has consequences for carbon uptake by photosynthesis and release by total ecosystem respiration. After a drought the disturbances in the reservoirs of moisture, organic matter and nutrients in the soil and carbohydrates in plants lead to longer-term effects in plant carbon cycling, and potentially mortality. Direct and carry-over effects, mortality and consequently species competition in response to drought are strongly related to the survival strategies of species. Here we review the state of the art of the understanding of the relation between soil moisture drought and the interactions with the carbon cycle of the terrestrial ecosystems. We argue that plant strategies must be given an adequate role in global vegetation models if the effects of drought on the carbon cycle are to be described in a way that justifies the interacting processes.