基于土壤微波辐射布儒斯特角反演土壤含水率

在利用被动微波遥感技术进行裸露地表土壤含水率（Soil Moisture Content,SMC）的反演中,土壤粗糙度是制约反演精度的最关键因素。该研究利用改进的积分方程模型（Advanced Integral Equation Model,AIEM）进行地表多角度微波发射率的模拟,探索地表微波辐射多角度信息用于提高地表SMC反演精度的可行性。基于不同SMC和不同粗糙度地表多角度V极化发射率数据的变化趋势提取土壤介质布儒斯特角,结果表明,土壤布儒斯特角对SMC具有较高的敏感性,C波段（6.6 GHz）不同含水率土壤的布儒斯特角分布在60°～80°范围内。基于AIEM模拟数据的分析发现,土壤布儒斯特角正切值与SMC具有较好的线性关系,线性拟合决定系数为0.94,均方根误差为0.027 cm3/cm3,并得到了基于布儒斯特角的裸露地表SMC反演算法。基于模拟数据的算法验证结果表明,算法的SMC预测值与理论值的决定系数为0.95,均方根误差为0.024 cm3/cm3。算法在不同土壤粗糙度自相关函数下均表现出稳健的特性,SMC预测精度最大均方根误差为0.027 cm3/cm3,最小为0.023 cm3/cm3。基于布儒斯特角的SMC反演算法利用的是多角度土壤发射率的相对变化而非其绝对数值,该研究为SMC的多角度被动微波遥感提供了一种不同的研究思路。     

Evaluation of Indian rock phosphates for predicting agronomic potential through chemical and biological methods

ABSTRACT

The chemical reactivity of Indian rock phosphates (RPs) was measured by five chemical extraction methods (i.e. water, neutral ammonium citrate (NCA), 2% citric acid (CA), 2% formic acid (FA) and absolute citrate solubility (ACS)). These measurements were assessed by agronomic response data obtained by growing ryegrass and palmarosa in two highly weathered acidic soils under pot culture experiment. The phosphorus (P) solubility value of RP measured by different methods followed the order: ACS > 2% CA > 2% FA > NAC > water. Considering triple superphosphate (TSP) as a standard reference P fertilizer, the agronomic response of RPs followed the order Udaipur RP > Jhabua RP ≥ Purulia RP > Mussorie RP. Methods based on citrate solubility (i.e. NAC, 2% CA and ACS) were significantly and positively correlated with agronomic response irrespective of the plant species and soil types. The best correlation value obtained with NCA indicated that P solubility in NAC solution may offer better prediction of agronomic effectiveness of RP in terms of biomass yield, relative agronomic efficiency (RAE) and P recovery efficiency. So, the present investigation will help to predict the agronomic effectiveness of low-grade RP based on chemical methods.     

小麦秸秆覆盖量对坡面流水动力学特性影响

为系统研究小麦秸秆覆盖量对坡面流水动力学特性的影响,采用室内定床模拟试验,探究在不同流量(3.0、4.5、6.0、7.5、9.0 L/min)和坡度(3°、5°、10°、15°)下,坡面流水动力参数随秸秆覆盖量(0、1.5、2.5、3.5、4.5 t/hm²)的变化特征。结果表明：1)秸秆覆盖显著影响坡面流流型,在不同流量和坡度下,无秸秆覆盖时坡面流型均为急流,而在秸秆覆盖条件下,坡面流型均变为缓流。当流量≤7.5 L/min时,流态均为层流,当流量>7.5 L/min时,流态均为过渡流。2)随着秸秆覆盖量的增加,坡面流流速分别较裸坡降低了47.85%、53.86%、57.69%、60.11%。3)不同覆盖量下,坡面流流态指数随坡度的变化规律不一致。覆盖量≤2.5t/hm²时,随坡度的增加,流态指数呈先增后减的变化趋势,覆盖量>2.5 t/hm²时,流态指数随坡度的增加而逐渐减小。4)不同覆盖量下,坡面流阻力系数随坡度的变化规律不一致。秸秆覆盖坡面阻力系数是裸坡的9.36～19.68倍。低覆盖量下(≤2.5t...     

Effect of crop residue biochar on soil acidity amelioration in strongly acidic tea garden soils

Strongly acidic soil (e.g. pH < 5.0) is detrimental to tea productivity and quality. Wheat, rice and peanut biochar produced at low temperature (max 300 °C) and differing in alkalinity content were incorporated into Xuan‐cheng (Ultisol; initial pH_{soil/water = 1/2.5} 4.12) and Ying‐tan soil (Ultisol; initial pH _{soil/water = 1/2.5} 4.75) at 10 and 20 g/kg (w/w) to quantify their liming effect and evaluate their effectiveness for acidity amelioration of tea garden soils. After a 65‐day incubation at 25 °C, biochar application significantly (P < 0.05) increased soil pH and exchangeable cations and reduced Al saturation of both tea soils. Association of H⁺ ions with biochar and decarboxylation processes was likely to be the main factor neutralizing soil acidity. Further, biochar application reduced acidity production from the N cycle. Significant (P < 0.05) increases in exchangeable cations and reductions in exchangeable acidity and Al saturation were observed as the rate of biochar increased, but there were no further effects on soil pH. The lack of change in soil pH at the higher biochar rate may be due to the displacement of exchangeable acidity and the high buffering capacity of biochar, thereby retarding a further liming effect. Hence, a significant linear correlation between reduced exchangeable acidity and alkalinity balance was found in biochar‐amended soils (P < 0.05). Low‐temperature biochar of crop residues is suggested as a potential amendment to ameliorate acidic tea garden soils.     

Wheat and Rye Differ in Drymatter Partitioning,Shoot-Root Ratio and Water Use Efficiency Under Organic and Inorganic Soils

Shoot-root ratio (S:R), dry matter partitioning (DMP), and water use efficiency (WUE) response of wheat (Triticum aestivum L.) vs. rye (Secale cereale L.) was investigated under organic [organic compost (OC), Miracle Grow (MG), sunshine peat moss (SPM), and Garden Basic peat humus (GBPM)], and inorganic soils [canyon soil (CS) and amarillo soil (AS)] in pot experiment at Dryland Agriculture Institute, West Texas A&M University, College Station, Texas, USA, during winter 2009–2010. The experiment was performed in completely randomized design (CRD) with three repeats. The objective of this experiment was whether S:R, DMP, and WUE of wheat versus rye differ under organic and inorganic soils. The results revealed that both crops responded differently in terms of S:R, DMP, and WUE under different organic and inorganic soils. Wheat had higher WUE than rye at different growth stages. Among the soil types, the three organic soils (MG, SPM, and GBPS) had higher WUE than the two inorganic (CS and AS) soils. The higher WUE of both crops when grown in organic soils such as MG, SPM, and GBPS was due to the higher dry matter partitioning to shoots and roots. The total dry weight plant^?1 showed positive relationship with WUE.     

土壤水流模式染色剂示踪及优先流程度评估

优先流是结构性土壤水分入渗的主要方式。为了直接利用土壤水流模式分析其优先流程度,该文采用亮蓝染色剂示踪原状与扰动土柱的土壤水运移,定量评估优先流的相对发育程度。研究结果表明原状土柱优先流发育,空间变异性强,受优先流通道的特征控制,其优先流水流模式以蚯蚓大孔隙流和土块裂隙优先流为主。扰动土柱的水流模式为活塞流,无优先流发育。该文提出了随深度变化的染色面积比的变异系数指示原状土柱优先流相对程度的评价准则:变异系数越低,优先流程度越高。变异系数≥0.5%为优先流程度一般发育,0.25%~0.5%之间为发育,≤0.25%为非常发育。并通过原状和扰动土柱灌溉模拟试验验证了评价准则的可靠性。     

伊朗西部不同土地利用方式下钙质土壤疏水性研究

Soil wettability and water repellency, two important soil physical properties, play an important role in water retention and water conductivity in arid and semi-arid regions. To date, there is a lack of information on soil water repellency in calcareous soils of western lran. In this study, soil water repellency and its affecting factors were studied using 20 soil series collected from Hamadan Province~ western Iran. The effects of soil properties including organic carbon content （SOC）, total nitrogen （TN）, C：N ratio, texture, CaCO3 content, and both fungal and bacterial activities on water repellency were investigated using air-dried, oven-dried and heated soil samples. Water repellency index （WRI） was determined using the short-time sorptivity （water/ethanol） method. To distinguish the actual effects of SOC, a set of soil samples were heated at 300 ~C to remove SOC and then WRI was measured on the heated samples. Relative water repellency index （RWRI） was defined as the change of WRI due to heating relative to the oven-dry WRI value. Results of the WRI values showed that the soils were sub-critically water-repellent. Pasture soils had higher WRI values compared to tilled soils, resulting from high SOC and TN, and high activities of bacteria and fungi. It was observed that SOC, TN, fungal activity, and SOC：clay ratio had significant positive impacts on WRI. Strong positive correlations of RWRI with SOC, TN and fungal activity were also observed. Pedotransfer functions derived for predicting WRI showed that the WRI values had an increasing trend with the increases in fungal activity, salinity, alkalinity and fine clay content, but showed a decreasing trend with increasing bacterial activity.     

Aspects of the adsorption and degradation of isoproturon in a heavy clay soil

Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (<3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.     

澳洲酸性硫酸盐土壤的特征、问题及管理

Acid sulfate voile (ASS), widely distributed in Australia. This has only been recognised recently when intensive rmearch on ASS has been done in this country. This paper reviews aspects concerning a) the distribution and acid potential, b) controls on acidic status, and c) problems and management of ASS in Australia. It is believed that the Australian experience may be useful for other countries where potential problems from ASS exist but insufficient attention was paid to them.     

Overcoming Fe deficiency in guava (Psidium guajava L.) by co-situs application of controlled release fertilizers

Abstract

Among micronutrient deficiencies, Fe deficiency is the most difficult nutritional disorder to prevent in the fruits of trees growing on calcareous soils. In this study, a pot experiment was carried out to evaluate the potential of co-situs application of controlled release fertilizers (CRF) in alleviating Fe deficiency and improving the growth of fruit trees growing on calcareous soil (pH 9.3). Guava (Psidium guajava L.) seedlings were used as test plants because of their sensitivity to Fe deficiency. Treatments consisted of the following: (1) broadcast application of readily soluble Fe, Zn, Cu, B and Mn fertilizers (Control) or (2) co-situs application of CRF containing N, P, K, Mg, Fe, Zn, B, Cu and Mn (Co-situs). For the Control treatment, CRF containing only N, P and K was used. Both treatments received the same amount of all nutrients. Plants were more chlorotic in young leaves under the Control treatment and the Fe content of young leaves was significantly (least significant difference [LSD_0.05]) higher under the Co-situs treatment. Dry matter production of shoots under the Co-situs treatment was 5.2-fold higher than under the Control treatment, and the total accumulations of macro and micronutrients were much higher under the Co-situs treatment than the Control treatment. Total accumulations of N, P, K, Ca and Mg were 5.0, 4.1, 9.6, 3.2 and 2.2-fold higher, respectively, under the Co-situs treatment compared with the Control treatment, and Fe, Zn, Cu and Mn accumulations were 3.2, 4.1, 6.0 and 3.7-fold higher, respectively. Iron deficiency in guava seedlings was successfully alleviated by the co-situs application of controlled fertilizer, proving the high potential of this method in alleviating Fe deficiency in fruit trees growing on calcareous soils.