Soil phosphorus dynamic, balance and critical P values in longterm fertilization experiment in Taihu Lake region, China

Phosphorus（P） is an important macronutrient for plant but can also cause potential environmental risk. In this paper, we studied the long-term fertilizer experiment（started 1980） to assess the soil P dynamic, balance, critical P value and the crop yield response in Taihu Lake region, China. To avoid the effect of nitrogen（N） and potassium（K）, only the following treatments were chosen for subsequent discussion, including： C0（control treatment without any fertilizer or organic manure）, CNK treatment（mineral N and K only）, CNPK（balanced fertilization with mineral N, P and K）, MNK（integrated organic manure and mineral N and K）, and MNPK（organic manure plus balanced fertilization）. The results revealed that the response of wheat yield was more sensitive than rice, and no significant differences of crop yield had been detected among MNK, CNPK and MNPK until 2013. Dynamic and balance of soil total P（TP） and Olsen-P showed soil TP pool was enlarged significantly over consistent fertilization. However, the diminishing marginal utility of soil Olsen-P was also found, indicating that high-level P application in the present condition could not increase soil Olsen-P contents anymore. Linear-linear and Mitscherlich models were used to estimate the critical value of Olsen-P for crops. The average critical P value for rice and wheat was 3.40 and 4.08 mg kg^（–1）, respectively. The smaller critical P value than in uplands indicated a stronger ability of P supply for crops in this paddy soil. We concluded that no more mineral P should be applied in rice-wheat system in Taihu Lake region if soil Olsen-P is higher than the critical P value. The agricultural technique and management referring to activate the plant-available P pool are also considerable, such as integrated use of low-P organic manure with mineral N and K.

SimET: An open-source tool for estimating crop evapotranspiration and soil water balance for plants with multiple growth cycles

Accurate estimation of crop evapotranspiration(ETc) and soil water balance, which is vital for optimizing water management strategy in crop production, can be performed by simulation. But existing software has many deficiencies, including complex operation, limited scalability, lack of batch processing, and a single ETc model. Here we present simET, an open-source software package written in the R programming language. Many concepts involved in crop ETc simulation are condensed into functions in the package. It includes three widely used crop ETc models built on these functions: the single-crop coefficient,double-crop coefficient, and Shuttleworth–Wallace models, along with tools for preparing model data and comparing estimates. SimET supports ETc simulation in crops with repeated growth cycles such as alfalfa, a perennial forage crop that is cut multiple times annually.

Study on Soil Respiration Characteristics and Carbon Balance of <i>Kobresia pygmaea</i>Meadow in Qinghai-Tibet Plateau, China

Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of extremely geographic situation. This study was designed to examine soil CO2 efflux characteristics of diurnal and seasonal variation, thus obtaining estimates of carbon balance of Kobresia pygmaea meadow in Qinghai-Tibet plateau. The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared. Composite model which was set by soil respiration rate, soil moisture content and temperature (atmospheric temperature and soil temperature) could explain better the variations of soil respiration rate. The variation range of Q10 ranged from 1.28 to 2.34, which was sensitive to temperature in green-up period and late growth stage, and decreased in growth peak period. Meanwhile, during the growing seasons the observed amount of annual carbon fixation via primary production for Kobresia pygmaea meadow ecosystem was about 120.21 g C·m-2·a-1. The carbon dioxide output via soil heterotrophic respiration was about 37.54 g C·m-2·a-1. So carbon budget had more input than output. The Kobresia pygmaea meadow ecosystem has stronger potential to absorb carbon dioxide, it was a sink of atmospheric CO2, and the plant community had a net carbon gain of 82.67 g C·m-2·a-1.

砒砂岩覆土区典型小流域土壤可蚀性K值空间变异特征

[目的]研究砒砂岩覆土区典型小流域土壤可蚀性的空间变异特征,为砒砂岩覆土区土壤侵蚀机理深入探究和土壤侵蚀有效防治提供科学依据。[方法]以内蒙古准格尔旗砒砂岩覆土区二老虎沟小流域为研究对象,采集0—10 cm和10—20 cm土层共144份土壤样品,基于EPIC模型估算土壤可蚀性K值,并利用GIS和地统计学方法分析土壤可蚀性K值空间变异特征。[结果](1)二老虎沟小流域土壤砂粒、粉粒、黏粒和有机碳均呈中等变异程度,除黏粒和有机碳为中等空间自相关性外,其他土壤属性均呈弱空间自相关性。(2)小流域土壤可蚀性K值介于0.018 7~0.047 6 t·hm^(2)·h/(hm^(2)·MJ·mm),0—10 cm和10—20 cm土层K值变异系数分别为15.5%和20.3%,属中等变异强度;0—10 cm土层K值主要受随机性因素影响,呈弱空间自相关性,而10—20 cm土层受随机性因素和结构性因素共同影响,为中等空间自相关性。(3) 3种克里格插值方法结果表明:小流域土壤可蚀性K值空间变异受海拔和坡度影响明显,其总体分布趋势为西部和东南部较高、中部及偏东部较低;普通克里格插值方法较适宜应用于砒砂岩覆土区小流域,其估算结果可较好地显示土壤可蚀性的整体和局部两方面的空间变异特征。(4)在垂直空间变异上,0—10 cm和10—20 cm土层土壤可蚀性K值总体分布规律相似,但10—20 cm土层土壤可蚀性K值较0—10 cm土层空间变异更为明显。[结论]海拔和坡度对砒砂岩覆土区典型小流域土壤可蚀性K值空间变异影响明显,未来应优先对坡面和坡顶区域进行土壤侵蚀防治。

Antecedent Precipitation Index to Estimate Soil Moisture and Correlate as a Triggering Process in the Occurrence of Landslides

Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbanized slope regions, especially those considered high-risk areas. Various other factors contribute to the process;thus, it is essential to analyze the causes of such incidents in all possible ways. Soil moisture plays a critical role in the Earth’s surface-atmosphere interaction systems;hence, measurements and their estimations are crucial for understanding all processes involved in the water balance, especially those related to landslides. Soil moisture can be estimated from in-situ measurements using different sensors and techniques, satellite remote sensing, hydrological modeling, and indicators to index moisture conditions. Antecedent soil moisture can significantly impact runoff for the same rainfall event in a watershed. The Antecedent Precipitation Index (API) or “retained rainfall,” along with the antecedent moisture condition from the Natural Resources Conservation Service, is generally applied to estimate runoff in watersheds where data is limited or unavailable. This work aims to explore API in estimating soil moisture and establish thresholds based on landslide occurrences. The estimated soil moisture will be compared and calibrated using measurements obtained through multisensor capacitance probes installed in a high-risk area located in the mountainous region of Campos do Jordão municipality, São Paulo, Brazil. The API used in the calculation has been modified, where the recession coefficient depends on air temperature variability as well as the climatological mean temperature, which can be considered as losses in the water balance due to evapotranspiration. Once the API is calibrated, it will be used to extrapolate to the entire watershed and consequently estimate soil moisture. By utilizing recorded mass movements and comparing them with API and soil moisture, it will be possible to determine thresholds, thus enabling anticipation of landslide occurrences.

有限深度介质上梁非线性能量汇减振的Winkler地基实现

土-结构相互作用对结构动力学特性的影响是一种具有非线性能量汇特征的效应。利用考虑土体质量的Winkler地基梁理论,将有限深度弹性介质等效为非线性能量汇系统的附加质量,建立简谐激励下弹性介质上简支梁系统的非线性动力学模型。采用Galerkin方法和增量谐波平衡法分析了弹性介质上简支梁的非线性动力响应。利用数值计算方法验证了理论结果的正确性,并分析了非线性能量汇的有效性。通过参数优化和分析,揭示了不同参数范围内Winkler地基的减振效果,讨论了其最佳参数范围。研究结果表明:在合理的参数范围内,弹性介质对其支承梁的动力响应有良好的抑制作用,能够快速有效地吸收共振条件下的振动能量,并具有良好的鲁棒性。优化后的非线性能量汇可使梁的共振幅值降低超95%,且具有较宽的减振频带。研究成果从非线性能量汇的角度展现了土-结构相互作用效应的减振机理,为基于弹性地基设计的结构振动抑制提供了理论依据。

Study on the Balanced Fertilization forCorn in Black SoilRegion

Regressive models were obtained by employing '311 B' and '3414' optimal regressive desingns through 5 year (1993～1997) field experiment,and by datum processing with computer.These models express the relationships between corn yields in high,middle and low yield areas and N,P,and K application rates in black soil.By analysis to the models,the fertilizer application rates for maximum yield and optimal yield were achieved.

Effect of Long-Term Application of K Fertilizer and Wheat Straw to Soil on Crop Yield and Soil K Under Different Planting Systems

Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertilizer and wheat straw to soil in Hebei fluvo aquic soil and Shanxi brown soil in northern China were begun in 1992. The results showed that K fertilizer and straw could improve the yields of wheat and maize with the order of NPK ＋ St 〉 NPK 〉 NP ＋ St 〉 NP, and treatment of K fertilizer made a significant difference to NP, and the efficiency of K fertilizer in maize was higher than in wheat under rotation system of Hebei. In contrast with Shanxi, the wastage of soil potassium was a more serious issue in the rotation system in Hebei, only treatment of NPK ＋ St showed a surplus of potassium and the others showed a wane. K fertilizer and straw could improve the content of water-soluble K, nonspecifically adsorbed K, non-exchangeable K, mineral K, and total K in contrast to NP; however, K fertilizer and straw reduce the proportion of mineral K and improve proportion of other forms of potassium in the two locating sites. Compared with the beginning of orientation, temporal variability character of soil K content and proportion showed a difference between the two soil types; furthermore, there was a decrease in the content of mineral K and total K simultaneously in the two locating sites. As a whole, the effect of K fertilizer applied to soil directly excelled to wheat straw to soil. Wheat straw to soil was an effective measure to complement potassium to increase crop yield and retard the decrease of soil K.

Effects of cotton field management practices on soil CO2 emission and C balance in an arid region of Northwest China

Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods（drip and flood）, stubble managements（stubble-incorporated and stubble-removed） and fertilizer amendments（no fertilizer（CK）, chicken manure（OM）, inorganic N, P and K fertilizer（NPK）, and inorganic fertilizer plus chicken manure（NPK＋OM））. The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK＋OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK＋OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity（NEP） under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK＋OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK＋OM or NPK could increase soil C storage in cotton fields of Northwest China.

The Impact of Soil Freezing/Thawing Processes on Water and Energy Balances

A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular, soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezingthawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods.

Soil quality and sustainable land use in urban-rural marginal area: a case study of Kaifeng

By using the basic theories of physical geography, land resources and ecology, this article analyzes the soil quality of the rural-urban marginal area in Kaifeng. Computer techniques, based on soil samples analysis, are used to study soil quality changes in the Kaifeng’s rural-urban marginal area. While focusing on nutrient circle key links of input and output in soil, relying on numerous practical survey data, this article reveals clearly the impact of land use change on soil quality.

Regional Evaluation of Winter Rapeseed Response to K Fertilization, K Use Efficiency, and Critical Level of Soil K in the Yangtze River Valley

The investigation was carried out to study the response of winter rapeseed to potassium （K） feritlization and the critical soil available K level for current winter rapeseed production in the Yangtze River Valley （YRV） of China. A total of 132 field experiments were conducted in fields of farmers in the major winter rapeseed growing areas in YRV in 2000/2001 and 2004/2005 to 2006/2007 during growing season. Results of these field experiments showed that the average rapeseed yield increment resulting from 100 kg K ha-1 application was 358 kg ha-1, an increase over the control CK （no K） of 18.0% in 2005/2006 and 2006/2007. The average internal use efficiency （IE） of K was higher in the CK treatment （21.9 kg grain, kg-1 K uptake） than in the ＋K （100 kg K ha-1） treatment （17.7 kg grain, kg-1 K uptake）. Winter rapeseed required 68.1 kg of K to produce 1 000 kg seed. The recovery efficiency of K fertilizer in rapeseed production averaged 39.3%. The K balance was negative, with an average net removal of 117.6 kg K ha-1 in the CK treatment annually, and 56.8 kg K ha-1 in the ＋K treatment. The results indicated that there was a significant negative relationship between yield increments by K application and soil available K content. Based on the relative yield of CK/＋K at 90% level, the critical level of soil available K （NH4OAc-extractable K） was 135 mg kg-1.

Detection of K in soil using time-resolved laser-induced breakdown spectroscopy based on convolutional neural networks

One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy(LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem,this paper investigated a combination of time-resolved LIBS and convolutional neural networks(CNNs) to improve K determination in soil. The time-resolved LIBS contained the information of both wavelength and time dimension. The spectra of wavelength dimension showed the characteristic emission lines of elements, and those of time dimension presented the plasma decay trend. The one-dimensional data of LIBS intensity from the emission line at 766.49 nm were extracted and correlated with the K concentration, showing a poor correlation of R_c^2?=?0.0967, which is caused by the matrix effect of heterogeneous soil. For the wavelength dimension, the two-dimensional data of traditional integrated LIBS were extracted and analyzed by an artificial neural network(ANN), showing R_v^2?=?0.6318 and the root mean square error of validation(RMSEV)?=?0.6234. For the time dimension, the two-dimensional data of time-decay LIBS were extracted and analyzed by ANN, showing R_v^2?=?0.7366 and RMSEV?=?0.7855.These higher determination coefficients reveal that both the non-K emission lines of wavelength dimension and the spectral decay of time dimension could assist in quantitative detection of K.However, due to limited calibration samples, the two-dimensional models presented over-fitting.The three-dimensional data of time-resolved LIBS were analyzed by CNNs, which extracted and integrated the information of both the wavelength and time dimension, showing the R_v^2?=?0.9968 and RMSEV?=?0.0785. CNN analysis of time-resolved LIBS is capable of improving the determination of K in soil.

Evapotranspiration and Soil Moisture Balance for Vegetative Restoration in a Gully Catchment on the Loess Plateau, China

Evapotranspiration, soil moisture balance and the dynamics in a gully catchment of the Loess Plateau in China were determined with 6 land use treatments including natural grassland, shrubs (Caragana microphylla), two woodlands (Prunus armeniaca var. ansu and Pmus tabulaeformis), cultivated fallow, and farmland (Triticum aestivum L.) in order to obtain a better understanding of soil moisture balance principles and to improve vegetation restoration efficiency for ecological rebuilding on the plateau. Average runoff from cultivated fallow was very high, reaching 10.3% of the seasonal rainfall. Evapotranspiration under T. aestivum was not significantly different from natural grasslands. Compared with natural grass, evapotranspiration was significantly greater (P < 0.05) in 2002 and there was an increase in soil moisture depleted in the 1-3 m soil under P. armeniaca, P. tabulaeformis and C. microphylla. During the two years of the study the average soil moisture (0-100 cm soil profile) of T. aestivum was generally the highest, with P. armeniaca, P. tabulaeformis and C. microphylla usually the lowest. Thus, according to the soil moisture balance principle for this area the planned reforestation project was not ecologically reasonable. Reducing human disturbance and restoration with grass could be more effective.

Nutrient Cycling and Balance in Red Soil Agroecosystem and Their Management

An experiment was conducted in a red soil derived from Quaternary red clay in the Ecological ExperimentStation of Red Soil, the Chinese Academy of Sciences, located in Yingtan (28° 15′ 30″ N, 116° 55′ 30″E), Jiangxi Province. The results show that the major ways of nutrient loss are leaching and nitrogenvolatilization. Rationalizing crop distribution, stimulating nutrient recycling, and improving internal nutrientflow are effective measures to decrease nutrient loss and to promote nutrient utilization efficiency. Theimportant ways of regulating nutrient cycling and balance in the agroecosystem of the red soil are to establishoptimal eco-agricultural models, practice balanced fertilization and combine the cropping system with thelivestock system.

Nutrient Balance in Relation to High Yield and Good Quality of Potato on an Acid Purple Soil in Chongqing,China

A field experiment was carried out to study nutrient balance among N, P, K and Mg in potato cultivation on an acid purple soil in Chongqing, China. The experiment included 8 treatments with equal P rate of 120 kg P2O5 hm-2: N0K2, N1K2, N2K2, N3K2, N2K0, N2K1, N2K1Mg and N2K3, where N0, N1, N2 and N3 stand for the N rates of 0, 75, 150 and 225 kg N hm-2, and K0, K1, K2 and K3 for the K rates of 0, 165, 330 and 495 kg K2O hm-2, respectively. Among the treatments designed, Thatment N2K2 with a nutrient supply ratio of N:P2O5:K2O:MgO = 1.25:1:2.75:0.28 gave the highest tuber yield and dry matter, highest starch and Zn and lowest NO3- contents in tuber, and high N, P and K use efficiency with an uptake ratio of N:P:K:Mg = 11.38:1:13.32:0.33 by tuber. Yield and starch and protein contents of tuber were the lowest in Treatment N0K2. Dry matter was the lowest but protein and NO3- contents were the highest in Treatment N2K0. Treatment N2K1Mg had the highest N, P and K utilization rates. Statistical analysis showed that yields of tuber and starch were in a positive linear correlation with the uptake amount of various nutrients and protein of the potato tuber was in a significantly positive linear correlation with tuber N cotent and in a significantly negative linear correlation with tuber K and Mg contents. Balanced application of N, P, K and Mg fertilizers (Treatmeat N2K2) was recommended for realization of high yield and good quality in potato cultivation.

Optimization of constitutive parameters of foundation soils k-means clustering analysis

The goal of this study was to optimize the constitutive parameters of foundation soils using a k-means algorithm with clustering analysis. A database was collected from unconfined compression tests, Proctor tests and grain distribution tests of soils taken from three different types of foundation pits： raft foundations, partial raft foundations and strip foundations. k-means algorithm with clustering analysis was applied to determine the most appropriate foundation type given the un- confined compression strengths and other parameters of the different soils.

Kinetics of K Desorption from Soils in a Constant Electric Field (Electro-Ultrafiltration) and Its Application

K desorption from soils in a constant electric field(field strength:44.5V cm^-1) by means of electro-ultrafiltration (EUF) followed second-order kinetics and could be described by the equation dd/dt=k(D-d)^2.From the equation,such inetic parameters relating to K desorption from soils as the maximum desorbable quantity D,quantity of K desorbed within 40 minutes d40,initial desorption rate Vo,desorption rate constant k and half time t1/2 could be calculated.An expression which describes the relationships between the kinetic parameters on the one hand and the responses of barley to fertilizer-K in the field experiments in different sites and the potassium-supplying power of soils on the other was established.Vo,D and d40 were significantly correlated with barley relative yield,K uptake by barley and the content of soil available potassium.The rate constants of K desorption varied between 4.42×10^-4-1.80×10^-3kg mg^-1 min^-1 and highly correlated with the relative yield of barley.The kinetic parameters including Vo,D,d40 and k were successfully used to estimate the K-supplying power of soils.