碳酸钙和根际作用对酸性红壤解磷微生物丰度的影响

选用玉米品种郑单958为试验材料,设置不添加碳酸钙(CK)、每千克土添加0.3g碳酸钙(Ca-0.3)和0.5g碳酸钙(Ca-0.5)3个碳酸钙处理,以相应处理未种植物土壤为非根际对照土壤,研究了碳酸钙和根际作用对酸性红壤磷酸酶活性及解磷微生物相关功能基因phoC和phoD丰度的影响。结果表明:碳酸钙添加能有效改善玉米生长,促进地上部氮、磷、钾和钙的吸收。土壤酸性磷酸酶(ACP)活性显著高于碱性磷酸酶(ALP)活性,表明酸性土壤中ACP在矿化有机磷方面占主导地位。根际土壤ACP、ALP活性和phoD基因拷贝数均显著高于非根际,而仅Ca-0.5处理ALP活性和phoD基因拷贝数显著高于CK,说明根际效应强于碳酸钙处理。phoC基因拷贝数与土壤铵态氮、硝态氮含量存在显著相关性,ALP活性和phoD基因拷贝数与土壤pH及铵态氮、硝态氮、有效磷、交换性钙含量均存在显著相关性。可见,碳酸钙和根际作用均影响酸性土壤解磷微生物功能和丰度,但根际效应更加明显,这些作用与土壤理化因子的改变密切相关。     

填埋复垦侵蚀沟的导排水功能和秸秆腐解速率

秸秆填埋复垦技术主要用于修复东北地区耕地中的侵蚀沟，研究复垦后原沟道的导排水能力以及秸秆的腐解速率，旨在为沟毁耕地修复提供科学依据。该研究在黑龙江省海伦市光荣村选取一条复垦后的侵蚀沟为试验区，对土壤入渗能力、渗井入渗能力、秸秆层的持水能力、复垦后的土体排水能力系统测定分析，评价复垦后的导排水能力；对填埋不同年限的秸秆取样分析，评价秸秆腐解速率。结果表明：1）复垦后原沟道位秸秆层储水量为463 kg/m3，雨季产生径流能够完全被秸秆层储存，复垦后耕地能承受44～80 mm/h的均匀降雨，95%的地表汇流转为地下径流，大大减少径流对地表的冲刷，实现了变地表径流为地下导排水，复垦后未二次冲刷成沟。2）秸秆捆的厚度平均每年下降1.4 cm，秸秆层下降部分可被春季翻耕以及雨季汇流带来的泥沙沉积填充，复垦后原沟道位未出现塌陷。3）经过20 a的填埋，秸秆不同组分的腐解速率不同，其中半纤维素与纤维素腐解较快，木质素几乎不发生腐解，其占比由26.8%上升至38.8%。填埋的秸秆长期处于厌氧环境，且被水浸泡，约半年处于冻结状态故腐解缓慢。秸秆填埋侵蚀沟，可以修复沟毁耕地，实现复垦和地块的完整，可广泛用于东北黑土区约20万条耕地中侵蚀沟的修复。     

休闲农业-旅游新看点

从休闲农业产生的背景、内涵、条件和运营方式等方面分析了休闲农业发展的重要性和必然性,并介绍了休闲农业发展的前景。     

黑垆土有机碳在团聚体中的分配及其保护机制

以黄土高原广泛分布的黑垆土为研究对象,研究了6个粒级团聚体中总有机碳(TOC)、稳定性有机碳(St OC)、矿物保护态有机碳(MOC)、化学稳定性有机碳(ROC)和游离氧化铁(Fed)、无定形氧化铁(Feo)、络合态氧化铁(Fep)以及黏土矿物含量的特征,重点分析了有机碳在各粒级团聚体中的分配及其与黏土矿物和各种形态氧化铁之间的相关性,及探讨了有机碳的保护机制。结果表明:黑垆土中约80%的土壤有机碳赋存于0.5~0.25、0.25~0.05和0.05 mm的3个粒级团聚体中;黑垆土中的有机碳以St OC为主,其含量随着团聚体粒级的减小而增加。在0.5~0.25和0.25~0.05 mm团聚体中,TOC含量与Fed含量呈正相关关系,相关性系数(r)均为0.72(P0.05);在0.25~0.05 mm粒级团聚体中,ROC含量与Fed含量呈正相关关系(r=0.68,P0.05),而St OC和MOC含量与伊利石含量具有正相关关系r分别为0.71(P0.05)和0.68(P0.05)。黑垆土中对有机碳起保护作用的主要是Fed和伊利石,但二者对有机碳的保护机制可能有所不同:Fed与有机碳络合形成化学稳定性有机碳,而伊利石主要通过吸附作用实现对有机碳的保护。     

基于水温对肉牛生长性能影响的冬季恒温饮水系统优选

为缓解西北地区拴系肉牛在冬季产生的冷应激,提高肉牛生长性能,研究根据连通器原理设计恒温饮水系统,为牛只提供温水。试验选取西门塔尔牛作为试验牛,对饮水器内水温、肉牛的饮水行为、生理以及日增质量进行测定。试验结果表明:恒温饮水系统能为处理组牛只提供17.69℃的温水,处理组牛的日增质量为1.53 kg/(d·头),较对照组提高0.36 kg/(d·头),差异极显著(P0.01)。在处理组中,牛只饮用16~18℃的温水表现出更多的饮水次数和更好的增重效果(日增质量达到(1.69±0.44)kg/(d·头))。饮水后牛只瘤胃处体表温度处理组比对照组高3.29℃,差异极显著(P0.01)。结果表明,在拴系肉牛舍中采用这种恒温饮水系统能够有效改善肉牛因冬季饮用冷水造成的冷应激,并能显著提高肉牛生长性能,具有技术和经济可行性。     

双行手扶式大蒜联合收获机设计和试验（英文稿）

为解决大蒜机械化收获时损伤率与损失率较高的问题，结合大蒜物理特性和种植模式，该研究设计了一种双行手扶式大蒜联合收获机，主要由挖掘装置，矫正装置，夹持装置，切割装置，收集装置等组成，可一次完成大蒜的挖掘，姿态矫正，夹持输送，茎根切割，低损收集等作业工序。为提高大蒜收获作业质量，采用Box-Behnken中心组合试验方法，以前进速度、挖掘深度、链条距离为试验因素，以损伤率和损失率为评价指标，进行参数优化试验。建立各影响因素与指标之间的回归数学模型，分析各因素对响应值的交互影响，获得最优参数组合为：前进速度0.51 m/s、挖掘深度97.2 mm、链条距离7.6 mm，对应的损伤率、损失率分别为0.65%、1.28%，对优化结果进行验证试验，试验结果表明在最优参数组合下，损伤率为0.63%、损失率为1.25%，各评价指标与预测值均很接近。研究结果可为大蒜联合收获机进一步完善结构设计和工作参数优化提供参考。     

Allelopathy variation in dryland winter wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) accessions grown on the Loess Plateau of China for about fifty years

In this study, we investigated the genetic variation of allelopathic potential, its grey correlation with important agronomic characters, and rank analysis on allelopathic stability of fifteen wheat accessions commonly grown in arid regions of the Loess Plateau in China. The genetic variation of allelopathic property in dryland winter wheat showed significant differences between accessions. Allelopathic effects exhibited high heritability (55–95%) throughout the life cycle of wheat. Heritability was highest in the tillering stage and weakest in the seed filling stage. Allelopathic potential varied and was discontinuous throughout the wheat life cycle. Grey correlation analysis indicated a close relationship between allelopathic potential dependant on growth phase and agronomic characters. Allelopathic expression during some growth periods induced a partial correlation effect on some important agronomic characters that affected wheat yield. Allelopathic heritability and its degree of influence on yield were more evident in the vegetative growth stage compared to the reproductive stage. A multiple linear regression was built between allelopathic potential during different growth periods and agronomic characters pursued in wheat breeding. Allelopathic potential had a linear effect on production traits cultivated in wheat breeding. When allelopathic intensity varied from 0 to 1 in the reproductive stage, plant height ranged from 44 to 108 cm, spike length from 6.4 to 9.2 cm, number of spikelets with seeds from 13.4 to 21.0, mean seed number per spike from 41.5 to 50.3 and thousand seed weight from 36.2 to 38.3 g. Based on rank analysis, we concluded that there was a synergistic relationship between allelopathic potential in wheat and genetic, chemical and ecological factors. Triticum aestivum L. ‘No 6 Lankao’ and T. aestivum L. ‘No 22 Xiaoyan’ were identified as stable and relatively strong allelopathic accessions, whereas T. aestivum L. ‘Lankao 95–25’ was a stable but relatively weak allelopathic cultivar. Other varieties showed unstable allelopathic potential.     

Antioxidant properties of crocin from Gardenia jasminoides Ellis and study of the reactions of crocin with linoleic acid and crocin with oxygen

Crocin-a water soluble carotenoid-is found in the fruits of gardenia (Gardenia jasminoides Ellis) and in the stigmas of saffron (Crocus sativus Linne). For crocin purification, gardenia fruits are extracted with 50% acetone, followed by ether washing, ion exchange, and separation by preparative HPLC. Purified crocin with purity of >99.6% has an antioxidative activity at concentrations up to 40 ppm. At 20 ppm the antioxidative activity of crocin is comparable to that of BHA. The antioxidant property of crocin as evaluated by the thiocyanate method was better than with the thiobarbituric acid method. The adduct between the linoleic acid radical and crocin was detected by LC-MS. When crocin reacted with oxygen in the presence of FeSO(4), intermediates such as monohydroperoxides and dihydroperoxides of crocin were formed and detected by LC-MS.     

A mycorrhizal pathogen (Glomus macrocarpum Tul. & Tul.) of tobacco: effects of long- and short-term cropping on the mycorrhizal fungal community and stunt disease

A crop rotation experiment was conducted on two adjacent tracts of land differing in long-term croppin history (30 year in tall fescue pasture or 3 year in sorghum-sudangrass hybrid (SSGH).. Short-term crops were 2 years in tobacco or low-endophyte (Acremonium coenophialum Morgan-Jones & Gams) tall fescue. Tobacco was grown on all plots in Year 3, and data relating mycorrhizal stunt disease of tobacco and populations of the stunt pathogen, Glomus macrocarpum Tul. & Tul., and of other members of the mycorrhizal fungal community, were taken. Disease incidence was highest with SSGH-tobacco and lowest with fescue-fescue, the other two combinations being intermediate. Mycorrhizal colonization was related to disease occurence. At the beginning of the season, populations of G. macrocarpum were equally high in land with a long-term history of SSGH, regardless of its short-term history; but at the end of the season, populations of G. macrocarpum among the four treatments were proportional to the incidence of disease. Populations of four mycorrhizal fungal species which were high in land with a short-term history of fescue were depressed by production of tobacco. Monocropping of tobacco appeared to narrow the diversity of the mycorrhizal fungal community and increased the proportion which is pathogenic, the overall result being lower productivity of soil for tobacco. Crop rotation of tobacco with fescue decreased the proportion of the mycorrhizal fungal community which is pathogenic and maintained productivity of soil for tobacco.     

Effect of organic matter on the distribution, extractability and uptake of cadmium in soils

Distribution and plant uptake of soil Cd as influenced by organic matter and soil type were investigated in a greenhouse experiment. Three soils (a sand, sandy loam and clay loam) were used. The rates of organic matter in its moist state added were 0,20,40, 80, 160 and 320 g kg^-1 of the air-dried soil on mass basis. Ryegrass (Lolium multörum L.) was used as a test crop. Soil Cd was analysed by a sequential extraction technique and by extraction with 1 M NH₄NO₃ and 0.005 M DTPA. The exchangeable fraction of Cd as determined by 1 M MgCl₂ in the sequential extraction procedure increased, whereas the Fe-Mn oxidebound fraction decreased, with increasing levels of organic matter addition in all three soils. The dry matter yields of ryegrass were not affected by the addition of organic matter, but the Cd concentrations in both cuts of ryegrass decreased with increasing amounts of organic matter added. The plant Cd was highly but negatively correlated to soil CEC. At any level of organic matter addition, the decrease in Cd concentration of ryegrass was in the order: sand > sandy loam > clay loam.