Soil physical conditions and root growth in coconut plantations interplanted with nitrogen fixing trees in Sri Lanka

The study was carried out to investigate the possibility of improving degraded soil conditions of Andigama series by intercropping coconut (Cocos nucifera L.) with Calliandra calothyrsus, Leucaena leucocephala, Acacia auriculiformis and Gliricidia sepium. Bulk density was significantly low in NFT interplanted plots followed by improved aeration in AB and B horizons of the soil profile. Total and readily available water fraction was higher in AB and B horizons of calliandra, acacia and gliricidia interplanted plots over control plots due to the increase of organic matter content and root growth. Root growth and proliferation of calliandra in A horizon were predominantly higher than that of leucaena, acacia and gliricidia species. In contrast, gliricidia roots penetrated into B horizon more densely than roots of other species. Better root growth of coconut in A horizon was observed in acacia and calliandra plots than other plots. The total coconut root biomass in AB and B horizons was higher in gliricidia and acacia plots than other species, which accounted for 91% and 0.3% in AB horizon and 21% and 23% in B horizon for gliricidia and acacia, respectively compared to the control. Total root biomass of coconut in calliandra plots was reduced by 5%, and 45% in AB and B horizons respectively. Results indicated that soil physical conditions of Andigama series (gravelly soil) could be significantly improved by interplanting acacia and gliricidia, as indicated by enhanced coconut root growth and proliferation. This revised version was published online in August 2006 with corrections to the Cover Date.     

淮北平原砂姜黑土玉米产量与土壤性质的区域分析

以淮北平原作为调查区域,对砂姜黑土区48个样点的玉米产量及0～20 cm耕层土壤性质进行了分析。结果表明:在涡阳县东、西部,蒙城县南部和怀远县北部,玉米产量多在8.7t/hm~2以上,土壤容重较小;而在蒙城县北部,玉米产量多在7t/hm~2以下,土壤容重最大,平均达到1.6g/cm~3以上。涡阳县土壤有机碳含量最高,平均值达到15.4g/kg,较怀远县和蒙城县分别增加了28.3%和55.9%。土壤全量养分和速效养分随玉米产量等级变化不明显。相关性分析表明:玉米产量与耕层土壤穿透阻力(r=–0.348,P0.05)、土壤容重(r=–0.484, P0.01)呈负相关,而与土壤有机碳(r=0.421, P0.01)呈正相关。因此,土壤物理性质与土壤有机碳是影响该区玉米产量的关键因子。     

马鞍列岛人工鱼礁区海域底质特征及其承载力

人工鱼礁是海洋牧场建设的重要组成部分,科学的选址是人工鱼礁区建设的必要环节。通过对浙江嵊泗马鞍列岛人工鱼礁区备选海域附近采集的底质柱状样品的分析,测得了每个站点底质柱样的粒度、含水率、天然密度等物理性质,以及贯入强度、抗剪强度等力学性质。用谢帕德和福克沉积物分类法分析粒度结果,发现所研究海域的底质由砂、粉砂、黏土构成,粉砂含量最高,主要以砂质粉砂为主。不同区域的底质因其粒度组分、孔隙率、天然密度等不同,其含水率不同,造成底质的承载力也不同。对底质物理性质与力学性质间的相关性分析表明,底质的含水率与贯入强度、抗剪破坏强度均存在较强的线性负相关,相关系数分别为–0.67和–0.64,可作为人工鱼礁投放底质适宜性评估的重要依据。通过建立底泥含水率与粒度间的回归方程可为大面积的底质承载力研究提供科学依据,并大幅降低调查的工程量。     

圆锥贯入过程的离散元仿真

以室内矾土颗粒、玻璃球和Toyoura砂的贯入试验结果为参考,利用离散单元法对圆锥贯入过程进行了数值仿真.数值仿真与室内试验结果对比表明:数值仿真得到的颗粒集合的贯入曲线与室内试验的结果较吻合,说明离散元法能够很好地模拟圆锥贯入过程中颗粒之间、颗粒与圆锥间的相互作用,并得到合理的宏观特性.仿真和室内试验都指出,随着孔隙率的增大,贯入阻力的数值随之减小.最后,就细观参数、贯入速度、试样颗粒数量及颗粒形状等因素变化对数值仿真结果的影响进行了分析.     

Screening and evaluation for antibiosis resistance of the spring wheat accessions to the grain aphid,Sitobion miscanthi (Takahashi) (Hemiptera: Aphididae)

Resistant cultivar deployment is an effective method for cereal aphid management.  Under greenhouse conditions, preliminary antibiosis resistance screening was conducted on 114 Ethiopian and 22 Chinese spring wheat accessions.  After performing a bioassay to determine antibiosis resistance, aphid feeding behaviour and phenolic acid content analyses were performed on the aphid resistant wheat accessions by electrical penetration graph (EPG) and high performance liquid chromatography (HPLC), respectively.  Among the wheat accessions, two high resistances, 27 moderate-resistances, and 35 low-resistances to Sitobion miscanthi were identified.  The antibiosis resistance test showed prolonged pre-adult and pre-reproductive periods, shorter reproductive periods, lower fecundity, an intrinsic rate (r_m) of increase, and a finite rate (λ) of increase of S. miscanthi on Lunxuan 145, Wane, Lunxuan 6, 204511, Lunxuan 103 and 5215 than those on the aphid-susceptible accession Beijing 837.  The changes for the parameters of aphid feeding behaviour, including spending a longer time in the penetration and phloem salivation phases and less time in the phloem sap-feeding phase on the resistant wheat accessions, the aphid resistance may occur during the phloem phase and may be due to mechanicalAdditionally, the HPLC analysis showed higher contents of: 1) ferulic acid in Lunxuan 145, Lunxuan 103 and Lunxuan 6; 2) p-coumaric acid in Lunxuan145; 3) vanillic acid in Lunxuan 145, Wane and Lunxuan 6; 4) syringic acid in Lunxuan 103; and 5) caffeic acid in 5215.  The contents of some phenolic acids within wheat leaves, such as p-courmaric acid and vanillic acid showed significant positive correlation with the duration of aphid development, but negative correlation with the aphid fecundity.  The concentrations of these acids may be the causes of antibiosis resistance to S. miscanthi.  The identification of grain aphid-resistant wheat accessions in our study will be helpful in future breeding program for pest control.     

Higher density swards have a higher load bearing capacity

Increasing the water table is an important pathway to reduce greenhouse gas emissions from peaty soils. In order to continue utilizing grasslands on these soils, methods to increase load bearing capacity at a higher water table are sought. The objective of this study was to assess the effect of sward density on load bearing capacity, measured as both penetration resistance and the newly developed method measuring load bearing capacity through impact depth. Simultaneously, a new method to measure load bearing capacity through impact depth was developed. The study was conducted between 2018 and 2020 on 14 different farms in the western peat meadow district in the Netherlands, where the sward density measured with the point quadrat method ranged from 24% to 92%. Swards with a higher sward density showed a higher load bearing capacity than swards with a lower density. In a modelling approach an increase from 30% sward density to 90% sward density could result in a lengthening of the grazing season between three (11%) and six weeks (22%), depending on the soil moisture conditions. Load bearing capacity was also highly correlated with gravimetric soil moisture content as wetter conditions lowered load bearing capacity. In order to capture load bearing capacity more accurately a new measurement device was constructed which represents treading cattle. Both output (impact depth) and method (resembles cow hoof) are close to practice, which makes it a very suitable method allowing for easy interpretation by farmers.     

鸡粪沼渣好氧堆肥颗粒尺度下氧气渗透深度表征

利用傅里叶变换显微红外光谱技术对鸡粪沼渣好氧堆肥颗粒尺度下氧气渗透深度进行了量化表征。用于表征鸡粪沼渣颗粒氧气渗透深度的显微红外透射光谱法的光谱采集范围为750~4 000 cm~(-1),光谱分辨率16 cm~(-1),像素点尺寸6.25μm×6.25μm,扫描次数8次。鸡粪沼渣好氧堆肥样品经冷冻干燥处理后,应采用石蜡切片技术制成12μm薄片,选取2 856 cm~(-1)和1 640 cm~(-1)代表脂肪类化合物,1 568 cm~(-1)和3 001 cm~(-1)代表芳香族化合物作为氧气渗透深度边界判定特征波长,且氧气渗透深度终点定义为差分曲线迅速下降处。鸡粪沼渣颗粒氧气渗透深度较小,介于7~20μm范围内动态变化,其符合指数关系式。研究结果表明,采用傅里叶显微红外透射光谱法判定好氧堆肥颗粒氧气渗透深度具有可行性,但应根据不同物料特性,选用适用的方法和技术参数。     

黄淮海旱作区农田耕层土壤结构特征与其影响因素

为探究黄淮海旱作区农田耕层结构特征,基于土壤穿透阻力数据,运用地统计学、Mann-Kendall突变检验法等方法,识别了旱作区农田压实层的位置及厚度,并探究了压实层和耕作层的空间变异特征及其影响因素.结果表明:土壤容重、含水率和土壤质地是穿透阻力的主要影响因素.和表层土壤相比,深层土壤穿透阻力更易受含水率和土壤质地的影...