烟稻轮作中稻草还田对土壤有机氮各组分的影响

以湘南烟区常年稻草还田与否的14个不同土样为研究对象,根据Keeney和Bremner土壤有机氮分级方法,研究湘南烟区烟稻轮作中稻草还田对土壤有机氮各组分含量及组成的影响。结果表明:稻草还田主要是提高了土壤有机氮组分中酸解未知态氮含量,而非土壤铵态氮、氨基酸态氮和酸不溶性氮含量差异的主导因素。稻草还田加强了铵态氮、酸解未知态氮和酸不溶性氮与有机质、全氮和碱解氮三者之间的相关性;减弱了氨基酸态氮、氨基糖态氮与有机质、全氮、碱解氮之间的相关性。     

Impact of very low crop residues cover on wind erosion in the Sahel

In the Sahel, with average annual precipitation in the order of 500 mm yr^− 1, wind erosion occurs mainly on cultivated millet fields whose surfaces are only partially covered by crop residues. The impact of these residues on wind erosion was not clearly established. The objective of this study is thus to quantify the actual amount of crop residues in traditional Sahelian fields and to determine their impacts on wind erosion by reference to a bare surface throughout the seasonal cycle over several years.     

不同土地利用类型下土壤-作物砷的积累特征及其健康风险分析

以菜地、稻田、果园、旱地等4种典型土地利用为研究对象,通过413个土壤和对应作物样品的测试分析,探讨了研究区不同土地利用方式下土壤及其种植作物的As积累特征和对人体的健康风险。结果表明,稻田土壤As含量在5.69～148.5 mg kg-1,积累程度最高;果园土壤As含量在3.29～24.7 mg kg-1积累程度最低。研究区各土地利用类型下土壤As变异系数均在0.5以上,为中等变异性,各样点之间土壤As含量变化较大。研究区不同土地利用方式下,作物As含量差异较大,油料作物As平均含量最高达2.15 mg kg-1,旱地谷物和水果As含量均值最低,均为0.032 mg kg-1。根据研究区作物As的富集系数进行聚类分析,将研究区作物划分为4类,油料作物富集系数最高可划分为第1类,水稻划分为第2类,叶菜类蔬菜划分第3类,而富集系数较低的水果、瓜果类蔬菜、豆荚类蔬菜、根菜类蔬菜和谷物划分为第4类。依据JECFA推荐的ADI值和研究区居民膳食结构进行计算,结果表明研究区不同土地利用类型土壤As对人体健康的风险为稻田>菜地>旱地>果园,尤其是稻田土壤As对人体健康的风险较大,因水稻食用导致的居民As摄入量高达0.0043mg人-1d-1,已面临较大的健康风险,应采取积极措施对研究区作物的种植结构进行调整,并对土壤As污染的区域进行治理和修复。     

Responses of fruit growth,quality, and productivity to crop load in apple cv. Ultra Red Gala/MM111

The effects of three crop load densities (4, 6 and 8 fruit per cm² of the cross-section of each tree branch, BCSA) on fruit growth, yield, fruit quality and vegetative growth were studied in apples (Malus × domestica Borkh) Ultrared Gala/MM111, from the fourth leaf (2006–2007 season) to the sixth (2008–2009 season). The maximum fruit growth rate was reached between 90 and 108 days after full bloom (DAFB), with values above 2.6 g day⁻¹. Accumulated yields to the sixth leaf reached 181, 157 and 123 Mg ha⁻¹ in the high, medium and low crop loads, respectively. Mean fruit weight decreased with increasing fruit crop load but the yields of fruit weight over 194 g were similar in all crop loads; the highest crop load exceeded the lowest crop load by 18.8 and 27.5 Mg ha⁻¹ of fruit weight of more than 172 and 154 g, respectively. The yields of harvested fruit exceeding 75% with red coloring did not show major differences, while fruit classified as 50–75% with red coloring were less common in the low crop load. No major differences were found at the end of the study in vegetative growth in the different seasons, nor in plant size. The reduction in mean fruit weight and in the percentage of fruit with good coloring was compensated by the increase in yields, thus not resulting in an effective reduction in the quality of the harvested fruit. The level of plant development reached with a semi-vigorous rootstock and high fruit loads allowed obtaining high fruit yield earlier and of good quality.     

“黑麦草一水稻”草田轮作系统的研究Ⅱ意大利黑麦草引进品种在南亚热带地区免耕栽培条件下的生产能力

应用从日本引进的５个意大利黑麦草品种（极早熟：樱早生，早熟：旱生丰、早生青叶，中熟：普通种，晚熟：双春），在我国南亚热带冬闲水田粗放条件（免耕，总施氮１５０ｋｇ／ｈｍ２）下进行栽培试验的结果表明：１）中、早熟品种在粗放条件下的干物质产量并不亚于在集约条件下的产量，说明ＩＲＲ系统是可以在粗放条件下高效运作的；２）晚熟品种不宜在粗放条件下的ＩＲＲ系统中应用；３）根系的强弱通过粗放条件下干旱胁迫的放大制约着ＩＲＧ的干物质产量，因此，具浅根系性状的极早熟品种未能表达其作为极早熟品种的产量优势，但亦达到了与其他中、早熟品种同程度的干物质产量，而其浅根系性状对于ＩＲＲ系统来说是极为重要的；４）粗放条件下ＩＲＧ的饲料营养性状受到很大影响，其粗蛋白质含量大大低于在集约条件下所得结果，但目前还不清楚这一变化是起因于氮投入的减少还是免耕措施。     

Irrigated Sweet Corn Crop Production Functions and Efficient Water Use1

The yield of sweet corn (Zea mays L.) and seasonal evapotranspiration as affected by different amounts of irrigation water was studied in a field plot experiment during 1991 and 1992 in the Jordan Valley. Four different amounts of irrigation water were imposed with trickle irrigation on a clay soil. The different sweet corn components differed in their response to seasonal evapotranspiration. Sweet corn yields of total fresh and total oven dry matter at W3 (W3 = E_o) and W4 (W4 =1.5 EJ were significantly higher than yields at lesser water amounts (W1 = 0.25 E_o and W2 = 0.5 EJ, while good husked fresh ear yield at W4 was significantly higher than yield at W1, W2, and W3. Seasonal evapotranspiration increased in a decreasing rate as total water applied increased. Increasing total water applied more than 400 mm resulted in a negligible increase in sweet corn seasonal evapotranspiration. Crop productivity and water use index (defined as the change in crop yield per unit change in seasonal evapotranspiration) were the highest, when optimal water levels were used.     

Methane oxidation in non-flooded soils as affected by crop production — invited paper

Methane is an important greenhouse gas, which contributes approximately 20% to global warming. The atmospheric CH₄ concentration is increasing rapidly, resulting from an imbalance between CH₄ production and consumption. The only known biological CH₄ sinks are soils where methanotrophic bacteria consume CH₄ by oxidizing it. For several reasons the CH₄ uptake potential, particularly of arable soils and grassland, is only partly exploited, as several agricultural practices have adverse impacts on the activity of the CH₄ oxidizing bacteria. The kind of land use in general has a remarkable influence with much higher oxidation rates under forest than under grassland or arable soil. Regular soil cultivation by ploughing and fertilization with ammonium or urea have been identified as main factors. Immediately after ammonium application the methanotrophic enzyme system is blocked, resulting in an inhibition of CH₄ oxidation. In addition to this short-term effect a long-term effect exists after repeated ammonium fertilization, which is most likely caused by a shift in the population of soil microbes. Crop residues affect CH₄ oxidation differently, depending on their C/N ratio: with a wide C/N ratio no effects are expected, whereas with a narrow C/N ratio strong inhibition was observed. Animal manure, particularly slurry, can cause CH₄ emission immediately after application, whereas in the long run farmyard manure does not seem to have adverse impacts on CH₄ oxidation. The methanotrophic activity decreased markedly with soil pH, although in many cases liming of acidified soils did not show a positive effect. Arable soils have a rather small pH range which allows CH₄ oxidation, and the inhibitory effect of ammonium can partly result from a concomitant decrease in soil pH. Reduced tillage was identified as a measure to improve the methanotrophic activity of arable land, set aside of formerly ploughed soil points into the same direction. Plant growth itself is not primarily responsible for observed effects on CH₄ oxidation, but secondary factors like differential pesticide treatments, changes in pH, or cultivation effects are more likely involved. Although for the overall CH₄ fluxes the oxidation processes in agricultural soils are of minor importance, all available possibilities should be exhausted to improve or at least preserve their ability to oxidize CH₄.     

Long-term energy use and economic evaluation of three tillage systems for cereal and legume production in central Spain

Three different experiments have been carried out in the area to the northeast of Madrid (central Spain) over 10 years with winter wheat (Triticum aestivum L.), winter barley (Hordeum vulgare L.), spring barley and vetch (Vicia sativa L.) grown for hay. In these experiments, three tillage systems were compared: conventional tillage (primary tillage was mouldboard ploughing to 300 mm depth), minimum tillage (primary tillage was spring tine cultivation either with a chisel or a cultivator to 150 mm depth) and zero tillage (direct drilling), in relation to energy consumption, production costs, energy efficiency and productivity, and economic returns. The experiments were performed on a Vertic Haploxeralf of a clay loam texture.The aforementioned variables were calculated considering every input (i.e. fertilisers, seeds, herbicides, machinery and fuel) including all the labour practices performed to harvesting. Post-harvesting activities were not included.The results showed that important energy and production cost savings may be achieved through minimum tillage and zero tillage, compared with conventional tillage. These energy savings ranged from 7 to 11% for cereal crops, whereas for vetch crops the reduction was 10% for minimum tillage and 15% for zero tillage. Production costs for minimum tillage were 13–24% less than for conventional tillage. For zero tillage these reductions ranged from 6 to 17%. For cereal crops, minimum tillage and zero tillage had energy productivities which were 18% and 20%, respectively, greater than that for conventional tillage. In most cases, yields of winter crops were similar, regardless of the tillage system considered. Only spring barley showed lower yields with zero tillage. For winter cereals the profitability with minimum tillage and zero tillage is higher than that with conventional tillage. However, spring barley is less profitable when using zero tillage.     

现代生物技术在蔬菜品种改良中的应用（上）

以细胞工程技术和基因工程技术为主体的现代生物技术在近十多年中得到快速发展。现代生物技术的广泛应用给传统的农作物品种改良带来了一场技术上的革命。主要介绍了国际国内植物细胞工程技术和基因工程技术在蔬菜品种改良方面的现状和展望。