华北平原旱地不同熟制作物产量、效益和水分利用比较

针对华北平原地下水超采严重,通过研究雨养旱作条件下不同熟制的产量、投入产出和水分利用效率,探索华北平原缺水区雨养旱作条件下的节水种植制度,可为地下水超采提供技术支撑。以当地主栽种植模式冬小麦和夏玉米一年2熟种植和春玉米一年1熟种植为研究对象,通过大田试验对雨养旱作条件下冬小麦、夏玉米和春玉米3种作物构成的2种种植制度的产量、耗水、投入、产出进行分析。试验于2007—2013年在中国科学院栾城农业生态系统试验站进行,该站为华北平原高产农区的典型代表。试验共设2个处理,T1为冬小麦-夏玉米一年2熟制,T2为春玉米一年1熟制。T1中的冬小麦生育期为每年的10月中上旬至翌年的6月中旬,夏玉米为6月中下旬至10月上旬,冬小麦品种大部分年份为‘科农199’,夏玉米品种为‘郑单958’。T2中春玉米的生育期为每年的5月中下旬至当年的9月上中旬,品种为‘农大108’、‘浚单20’、‘郑单958’和‘先玉335’。试验区从2007年9月至2013年6月一直未灌溉,为雨养旱作条件。研究结果表明,雨养旱作条件下,冬小麦产量基本稳定;夏玉米和春玉米产量随年型不同波动较大,尤其是夏玉米产量受播种时土壤含水量的影响较大,很多年份由于干旱少雨,玉米出苗时间推迟,导致玉米产量大幅度降低。T1比T2虽然具有明显的产量优势,增产34.1%,但由于冬小麦生产投入较高,T1的净收益比T2低279.97元·hm-2。3种作物的生产投入中,农资和机械投入比例最大,劳动力投入占很小比例,农资投入中,化肥投入最高;3种作物的产投比分别为1.42、2.66和3.42,雨养旱作条件下冬小麦的产投比最低,春玉米最高。从作物的耗水结构分析,冬小麦生育期降雨较少,以消耗雨季储存于土壤中的土壤水分为主,春(夏)玉米生育期降雨较多以消耗降雨为主。目前,生产上正在自发地压缩冬小麦的种植面积,春玉米一年1熟种植面积迅速增加。因此,在保证区域粮食安全的条件下,通过调整农业种植结构可以控制水资源的过度开采,保证农业持续发展。     

Carbohydrate dynamics in particle-size fractions of sandy spodosols following forest conversion to maize cropping

In southwest France, much of the forested land on sandy spodosols has been converted to continuous maize cropping in the last few decades. To evaluate the impacts of this change on soil organic matter properties, we compared total organic C and neutral and amino sugars content in whole soil and particle size separates of two forested, and five related sites that had been either clear-cut for 12 and 18 mo, or cultivated to maize for 4-22 yr. Soil carbohydrates accounted for 4-7% of the total organic C across all sites. Soil organic C contents of clear-cut and cultivated sites were only 57-79% of the average value measured in forested sites. Accordingly, carbohydrate content of clear-cut and cultivated sites were only 35-66% of the value in forested sites. Ordering the sites in a chronosequence indicated that both total organic C and carbohydrate contents decreased with an increase in time elapsed since clear-cutting and maize cultivation. The only exception was a partial recovery of carbohydrate content in the site that had been under continuous maize for 22 yr. The clay+silt fraction (0-50 μm) was enriched in carbohydrates, mainly of microbial origin, whereas the sand size fractions (50-200 and 200-2000 μm) contained fewer carbohydrates which were mainly of plant origin. Monosaccharide analysis of particle size separates revealed significant differences in carbohydrate composition between sites. Relative to forested sites, the coarse and fine sand fractions in clear-cut and cultivated sites were depleted in carbohydrates and were relatively enriched in plant-derived carbohydrates. Carbohydrate content of the clay+silt fraction drastically decreased upon clear-cutting. Amino sugar content was consistently lower in clear-cut and cultivated sites than in forested sites, indicating that microbial populations were negatively affected by clear-cutting and cultivation. The fungal population appeared more sensitive than bacteria to these land-use changes as indicated by a greater decline in glucosamine than in muramic acid contents.     

Bound amino acids in humic acids from arable cropping systems

We investigated the varying concentrations of bound amino acids in humic acids (HA) extracted from soils under both crop rotation and continuous cropping of rye. The experiment was created in 1957. Since then, winter rye had been grown continuously and also the sequence of the 7 yr rotation had been started: potato, spring barley, alfalfa, alfalfa, oil seed rape, winter rye, and winter rye. Soils were fertilized with NPK and manure. Continuous cropping of rye increased total acidity of soils and the contents of carboxylic and phenolic groups in HA. The total amounts of the bound amino acids in HA from soils under crop rotation were higher than from continuous cropping of rye. Fertilization with NPK increased the contents of bound amino acids more than manure. Neutral amino acids dominated in all samples of HA, and basic amino acids had the lowest concentrations. In both types of cultivation, glutamic acids, glycine, alanine, valine, and lysine dominated. The proline contents in HA from continuous rye cropping were higher than in HA from soils under crop rotation. The concentrations of β‐alanine and lysine were higher in HA from crop rotation indicating a higher microbial biomass since these compounds are typical constituents of bacteria cell walls.     

低丘红壤花生南酸枣间作系统研究 IV.光能竞争与剪枝作用

农林间作导致间作花生区域光合有效辐射和花生产量的下降,而且花生产量与光合有效辐射呈极显著正相关,表明了光能竞争是导致农林间作花生产量下降的主要原因。2001年6月初剪枝后,5龄和9龄南酸枣间作系统花生相对光合有效辐射分别从5月份的79.2%和63.4%增加到88.7%和67.5%; 但随着南酸枣生长,5龄和9龄南酸枣间作系统中7月份的花生相对光合有效辐射又下降到80.8%和65.7%。2001年剪枝以后,5龄南酸枣和9龄南酸枣间作系统花生相对产量分别由2000年的64.1%和55.4%提高到68.2%和58.1%。这表明剪枝在短期内能在一定程度上减轻光能竞争,但仍然不能满足花生生长需要。     

Sources of nitrogen and yield advantages for monocropping and mixed cropping with cowpeas (Vigna unguiculata L.) and upland rice (Oryza sativa L.)

Summary Sources of N used by cropped and intercropped cowpeas and rice were determined by the ¹⁵N isotope-dilution technique. The biological efficiency of intercropping cowpeas and rice was assessed by calculating the land equivalent ratio of dry matter yield, total N, and uptake of N. A reduced N uptake by both cowpeas and rice during mixed cropping was attributed to mutual competition, with both crops competing effectively for the scarce environmental resources. The lack of a significant difference in the uptake of fertilizer and soil N by mixed-crop rice and cowpeas is an indication that the soil N was sufficient and that the mixed cropping did not create any imbalance in soil and fertilizer N uptake. The land equivalent ratio ranged between 120% and 180% for shoot dry matter and total N, showing that biological efficiency was increased by intercropping cowpeas with rice. The proportion of N derived from the atmosphere by mono- and intercropped cowpeas was not significantly different, showing that the potential of cowpeas to fix N₂ was independent of the cropping system, since the rice did not stimulate the cowpeas to fix more N₂.     

黄瓜连作对土壤理化性状及生物活性的影响研究

盆栽与田间试验研究黄瓜连作对土壤理化性状及生物活性的影响结果表明,黄瓜连作后土壤次生盐渍化加重,P过剩,K则消耗过多,造成养分不平衡;土壤微生物区系改变,微生物由“细菌型”土壤向“真菌型”土壤转化,土传病虫害加重,线虫密度高达4.38条/g土。     

Comparisons of the influence of vesicular-arbuscular mycorrhiza on the productivity of hedgerow woody legumes and cassava at the top and the base of a hillslope in alley cropping systems

We investigated the influence of vesicular-arbuscular mycorrhizal (VAM) inoculation on growth and nutrient relationships in two alley-cropping trials, one at the top and the other at the base of a hillslope. Each trial involved three woody hedgerow legumes with cassava (Manihot esculenta Crantz) as the sole intercrop. The hedgerow trees at the base of the slope showed greater survival and higher leaf dry weights than those at the top of the slope, although these parameters were not affected by VAM inoculation, either at the top or the base of the slope. In contrast to survival, the uptake of nutrients, particularly P and N, was higher for inoculated than uninoculated hedgerow trees, both at the top and at the base of slope. Increases in stem and leaf biomass and the uptake of nutrients by the trees were strongly correlated with increases in P uptake, indicating that the improvements were attributable to VAM inoculation. Cassava tuber yields at the base of the slope, from inoculated or uninoculated plants, were significantly greater than the corresponding cassava yields at the top of the slope. These increases at the base of the slope compared to the top of the slope were not attributed to available soil nutrients but to greater VAM spore density. Higher available soil moisture may have been another factor. Increasing the VAM spore density of effective mycorrhiza through proper agronomic practices at the top of a slope may bring about comparable yields on different parts of the slope.     

杨树人工林连作效应的研究

通过对莒县沭河流域杨树人工林多代连作条件下林地土壤物理结构、养分特征、土壤酶活性、土壤微生物数量以及林分生长状况的系统研究,发现随着杨树连续栽植代数的增加,其林木的树高、胸径、材积呈明显的下降趋势。多重比较结果表明各代之间的树高、胸径、材积差异均达到了极显著的水平。连作后土壤的物理性状的变化不大,随林地代数的增加,土壤容重略有增大,毛管持水量、毛管孔隙度没有一定规律性。土壤pH值随连作代数的增加而减小。土壤养分随栽植代数的增加,总体呈逐代下降趋势。3代、4代林地与2代林地相比,林地表层土壤有机质及各层速效N、速效P、速效K及微量元素Cu,Zn大幅度下降,而Mn和Fe含量有增加的趋势。在0 2 0cm土层范围内,随连作代数增加,林地土壤脲酶、过氧化物酶、多酚氧化酶活性逐渐降低,其变化规律与土壤有机质和速效N ,P ,K含量变化规律相似。过氧化氢酶活性则有随着栽植代数的增加而增加的趋势。连作对杨树人工林土壤微生物数量有显著影响,随着连作代数的增加,土壤细菌、真菌、放线菌的数量大幅度下降     

大豆连作障碍及调控技术研究进展

综述了近 15年来有关大豆连作引起的根分泌物及残茬腐解物的自毒作用、植株营养失调、病虫危害加重、土壤微生物种群数量和生物肥力及土壤某些理化性质改变等障碍因素方面的研究 ,总结了提高连作大豆产量品质的主要调控措施。在此基础上 ,对有关研究需进一步关注的几个问题进行了讨论