Spatial variability of short-term effect of tillage on soil penetration resistance

The effect of tillage on soil properties varies within field due to spatial variability of soils. Mapping changes of soil penetration resistance (PR) would be useful to understand and assess tillage practices to alleviate soil compaction. The objectives were to model the short-term effect of tillage on PR and its spatial structure, and to delineate homogeneous zones based on soil response in a Typic Argiudoll previously managed under no-till. A grid sampling for PR and soil water content (SWC) were performed before and after chiselling. Spatial analysis was performed on the effect of tillage on PR data by 10 cm layers and homogeneous zones were delineated by k-means cluster analysis. The effect of tillage was ?0.33 MPa in 10–20 and 20–30 cm layer. No differences of PR were found at 0–10 cm. Short range (5–7 m) spatial structure on the horizontal plane was observed in all layers. Only 45% of the field showed a marked effect of tillage on PR. Mapping the effect of tillage on PR would be a useful approach for evaluating the global and local response of soil to tillage, as well as for delineating of areas within field for site-specific tillage practices.     

农业气象灾害对我国粮食生产的影响——基于八大经济区的面板数据回归

随着全球气候变暖的加剧，气象灾害频发对世界各国的农业生产构成了巨大威胁。本文基 于投入产出理论，通过分析我国八大经济区域1997-2018 年农业生产状况的面板数据，着重考虑了农 业气象灾害对不同地区粮食生产的影响程度，并基于分析结果提出了相应的建议。     

7个杂交黑麦草品种在云南不同气候带的产量比较试验

通过对7个杂交黑麦草品种在云南4个不同气候带的相对干物质产量以及各气候带杂交黑麦草与其亲本一年生黑麦草和多年生黑麦草各品种的平均产量比较分析,结果表明,杂交黑麦草的干物质产量介于其亲本之间,在云南及相似地区推广种植的优良杂交黑麦草品种为奥格斯塔杂交黑麦草。     

莫能菌素微生物检定法的改进

本试验对莫能菌素微生物检定条件的影响因素、微生物检定所用的菌种及培养基成分进行了改进。实验结果表明,采用枯草芽孢杆菌代替短小芽孢杆菌以及培养基中（ｐＨ６．５～６．６）加入适量的磷酸氢二钾用于莫能菌素微生物检定法测定效价,所得到的抑菌圈清晰,边缘光滑,无双圈,从而提高了效价测定的准确性。     

区域尺度地下水浅埋区拟二维水流数值模型

建立拟二维系统模型,在非饱和含水层采用沿平面积分得到的垂向一维方程,在饱和含水层采用沿侧向积分得到的垂向二维方程,推导了模型的动态耦合项,提出饱和-非饱和含水层迭代耦合算法,解决潜水面处网格变动问题。与SWMS_2D进行对比,采用垂向二维水分运动稳定流解析解算例验证拟二维模型的准确度,采用非稳定流算例验证拟二维系统模型对计算效率提升的显著性。     

沿海滩涂土壤盐分空间分布的三维随机模拟与不确定性评价

为揭示滨海滩涂地区土壤盐分三维空间分布特点并提供相关技术方法与思路,以苏北海涂围垦区典型地块为例,综合采用三维克里格和随机模拟方法对土体盐分含量的三维空间分布进行估值、模拟与对比分析,并对土体盐分三维分布的空间不确定性进行评价。结果显示,由克里格法得到的土壤盐分空间分布具有明显平滑效应,减小了数据间的空间差异并改变了数据的空间结构;序贯高斯模拟结果整体分布相对离散,突出了原始数据分布的波动性;研究区土壤盐分随深度增加而升高,存在一定次生盐渍化风险;围垦后研究区土壤盐渍化的发生概率已有所降低,轻度盐化土和中     

不同荒漠生态系统下有机碳和微生物碳的分布特征

基于新疆古尔班通古特沙漠南缘原始盐生旱生荒漠的3种建群灌木琵琶柴(Reaumuria soongori-ca)、多枝柽柳(Tamarix ramosissima)和梭梭(Haloxylon ammodendron)生态系统下土壤剖面实测数据,分析了土壤有机碳(SOC)和土壤微生物量碳(Mc)的垂直分布特征及其与土壤理化因子的关系。结果表明:3个生态系统类型之间土壤剖面SOC分布状况和含量不存在显著差别,但每个生态系统土壤剖面土层之间存在显著差别。各生态系统土壤上层均存在着一定厚度的SOC富集层,中部(10～30cm)SOC含量迅速下降,下部有机碳含量低而稳定。Mc分布与含量与SOC存在相似的规律。Mc对90cm以上的土壤碳循环起着重要的作用,而对深层次的碳库影响不大,不会对全球变化做出响应,但意义更重要,它们可以更长期保留于土壤中而不释放回大气圈。     

Maternal salinity environment affects salt tolerance during germination in Anabasis setifera: A facultative desert halophyte

The effects of maternal salinity and light incubation on the salinity tolerance of the facultative halophyte Anabasis setifera during their germination stages were assessed. Seeds were collected from non-saline habitats in Egypt and saline habitats in the United Arab Emirates(UAE). The seeds of the two populations were germinated in 0, 100, 200, 400, 600 and 800 m M Na Cl, and incubated at 25°C/15°C in both 12-h light and 12-h darkness regimes and continuous darkness. Significantly more seeds germinated in the Egyptian population than in the UAE population. Salinity tolerance was significantly greater with the Egyptian population than with the UAE population, especially under the conditions of higher salinities. The difference in salinity tolerance between the seeds of two populations was attributed to their seed mass. In addition, germination was significantly faster for the Egyptian population than for the UAE population. Most of the saline treated seeds were able to recover their germination when transferred to distilled water, but this depended on their maternal salinity and light incubation. Recovery from higher salinities was significantly better for the seeds under darkness than for those under light in the UAE population, but the reverse was true for the seeds in the Egyptian population. The higher salinity tolerance for the A. setifera seeds from the non-saline Egyptian population and the lower salinity tolerance for the seeds from the saline UAE population cannot explain their natural distribution. Further studies about other possible roles, such as levels of different promoting and inhibiting phytohormones, are needed to understand the importance of salinity as an environmentally induced maternal effect.     

Precipitation as the most affecting factor on soil–plant environment conditions affects the mycorrhizal spore numbers in three different ecological zones in Turkey

Mycorrhizal symbiosis is the one of the most important relationship between microbiota and plants to sustain plant nutrition in relatively unfavourable conditions. Somehow this relation is threatened by time, therefore, definition of the factors effecting mycorrhizal symbiosis has become essential. The aim of this study was to determine the differences in specific mycorrhizal parameters such as sporulation and soil–plant environment conditions in three different regions of Turkey. During 1996?2002, 53 soil series were selected from natural and agricultural plant communities in three different agro-ecological zones of Turkey: Central Anatolia (CA), the Southeastern Anatolian (SA) project area and the Coast of Mediterranean (CM). The arbuscular mycorrhizal fungus (AMF), spore numbers and mycorrhizal root colonization were related to the annual average precipitation, soil characteristics and host plant identity.

In the CM zone (average annual precipitation of 650?mm), soils found under natural vegetation contained a maximum value of 108?spores?g^?1, with bare soils containing a minimum number of 0.1?spores?g^?1. In the CA zone (330?mm annual average precipitation), the maximum number of spores in the soil samples was 46.5?spores?g^?1 with a minimum of 6.8?spores?g^?1 and in the SA soil samples (380?mm annual average precipitation), a maximum of 48.4?spores?g^?1 and a minimum of 14.2?spores?g^?1 were recorded. The overall mean number of mycorrhizal spores g^?1 soil was 15.5?±?14.4, 22.2?±?8.6 and 27.9?±?25.4 for the CA, SA and CM zones, respectively. Mean spore numbers differed in only two of the three zones, with the third zone being intermediate. Precipitation was the most affecting factor on the sporulation of AMF. Also host plant species and certain soil parameters, such as positive correlations with CaCO₃ and N-min and a negative correlation with organic matter, have an influence on sporulation.

The key finding is that the cropping system has a large impact on spore numbers/abundance. Seventeen standing crops as well as bare soil, fallow and natural areas were compared. There are a large number of factors which can affect mycorrhizal development; in the present work, it seems that soil and crop management, and environmental factors (such as precipitation) affect sporulation and root colonization. Covering land surface with mycorrhiza-dependent cover crop, irrigation and less soil till may increase indigenous mycorrhizal spores.