Simulation of Hail and Soil Type Effects on Crop Yield Losses in Kansas,USA

Computer simulation was used for predictive analysis of the effects of weather and soil type on crop yield in the U.S. crop insurance program. The Environmental Policy Integrated Climate （EPIC） model was modified to include hail weather events, which completed the modifications necessary to simulate the four most frequent causes of crop yield loss （hail, excessive wet, excessive cold, and excessive dry） associated with soil type in Kansas, USA. At the region level, per hectare yields were simulated for corn, wheat, soybean, and sorghum. We concluded that it was possible to predict crop yields through computer simulation with greater than 93% accuracy. The hail damage model test indicated EPIC could predict hail-soil-induced yield losses reasonably well （R^2 〉 0.6）. The investigation of soil type influence on dryland sorghum and wheat production indicated that Wymore silty clay loam soil and Kenorna silt loam produced the highest sorghum yields statistically; Kuma silt loam, Roxbury silt loam, Crete silty clay loam, and Woodson silt soils produced the second highest sorghum yields statistically; and Richfiled silt loam, Wells loam, and Canadian sandy loam produced the lowest sorghum yields. By contrast, wheat production showed less sensitivity to soil type variation. The less sensitive response of wheat yields to the soil type could be largely due to the unconsidered small-scale variability of soil features.

APEXeditor: A Spreadsheet-Based Tool for Editing APEX Model Input and Output Files

The APEXeditor, an Excel-based tool has been developed using the Visual Basic for Applications (VBA) to provide a graphical user interface (GUI) to the Agricultural Policy Environmental eXtender (APEX) model. APEX, in its native form, requires users to edit text files for modifying input files;therefore a GUI interface can aid users in modification of these files and reduce errors. Microsoft Excel is a popular spreadsheet program that has the largest user base among scientists and researchers, thus providing a relatively common platform in which stages the tool. The APEXeditor requires minimal additional learning to operate the tool for those who already have basic level of knowledge in Excel. The user can load APEX input files into the spreadsheet tool and the GUI offers meta information and provides functions to edit, write, and run the APEX model. Ultimately, the APEXeditor substitutes existing GUI programs such as WinAPEX or ArcAPEX that require installation or additional licensing. A series of scripts were developed as a back-end engine that automates data formatting and editing of linked APEX input ASCII files including database libraries. The simple architecture of the tool helps users maintain the quality of the data and allows error-free editing of APEX model inputs to characterize the system under study. This tool is suitable for all kinds of applications and has been successfully used for the creation of APEX model runs in numerous studies.

Laboratory and numerical modelling of irrigation infiltration and nitrogen leaching in homogeneous soils

Nitrogen (N) plays a key role in crop growth and production;however,data are lacking especially regarding the interaction of biochar,grass cover,and irrigation on N leaching in saturated soil profiles.Eighteen soil columns with 20-cm diameter and 60-cm height were designed to characterize the effects of different grass cover and biochar combinations,i.e.,bare soil+0%biochar (control,CK),perennial ryegrass+0%biochar (C1),Festuca arundinacea+0%biochar (C2),perennial ryegrass+1%biochar (C3),perennial ryegrass+2%biochar (C4),perennial ryegrass+3%biochar (C5),F.arundinacea+1%biochar (C6),F.arundinacea+2% biochar (C7),and F.arundinacea+3%biochar (C8),on periodic irrigation infiltration and N leaching in homogeneous loess soils from July to December 2020.Leachates in CK were 10.2%–35.3%higher than those in C1 and C2.Both perennial ryegrass and F.arundinacea decreased the volumes of leachates and delayed the leaching process in the 1%,2%,and 3%biochar treatments,and the vertical leaching rate decreased with biochar addition.The N leaching losses were concentrated in the first few leaching tests,and both total N (TN) and nitrate (NO_(3)^(-))-N concentrations in CK and C1–C8 decreased with increasing leaching test times.Biochar addition (1%,2%,and 3%) could further reduce the leaching risk of NO_(3)^(-)-N and the NO_(3)^(-)-N loss decreased with biochar addition.However,compared to 1%biochar,2% biochar promoted the leaching of TN under both grass cover types.The N leaching losses in CK,C1,C2,C3,C4,C6,and C7 were primarily in the form of NO_(3)^(-)-N.Among these treatments,CK,C1,and C2had the highest cumulative leaching fractions NO_(3)^(-)-N (>90%),followed by those in C3,C4,C6,and C7 (>80%).The cumulative leaching fraction of NO_(3)^(-)-N decreased with increasing leaching test times and biochar addition,and 3%biochar addition (i.e.,C5 and C8) reduced it to approximately 50%.The one-dimensional advective-dispersive-reactive transport equation can be used as an effective numerical approach to simulate and predict NO_(3)^(-)-N leaching in saturated homogeneous soils.Understanding the effects of different biochar and grass combinations on N leaching can help us design environmentally friendly interventions to manage irrigated farming ecosystems and reduce N leaching into groundwater.

APEX模型在淮河流域中上游的适宜性研究

探讨了APEX（Agricultural Policy／Environmental eXtender）模型在淮河流域中上游的适宜性。将APEX模型用于淮河流域中上游监测资料较匮乏的3个径流小区，用日径流／产沙的实测值和模拟值校正和验证模型，用校正过的模型评价不同土地管理措施的长期水土保持效益（1981～2005）。在模型校正阶段，3个小区日径流量和产沙量的平均百分误差绝对值（APE）小于20％，平均纳希-苏特克利夫有效系数（EF）大于0．6，平均尺。大于0．7；在模型验证阶段，3个小区日径流量和产沙量的平均APE小于12％，平均EF大于0．5，平均R^2大于0．7，APEX模型可模拟出径流、产沙的日变异。在水土保持效益评价结果中，与对照（休闲地）相比，管理措施2（林地-水平沟）的径流量平均减少37％，产沙量平均减少89％，管理措施1（林草混交-水平梯田）的水土保持效益要略低于管理措施2，构建水平沟、水平梯田以及增加地表植被是控制该地区水土流失的有效措施。研究结果表明：APEX模型适应性强，可用于预测和评价淮河流域中上游不同土地管理措施下的水土流失，这为资料匮乏地区研究土壤侵蚀提供了一种新的思路和工具。

Numerical Simulation on a Tremendous Debris Flow Caused by Typhoon Morakot in the Jiaopu Stream,Taiwan

In August 2009,Typhoon Morakot brought a large amount of rainfall with both high intensity and long duration to a vast area of Taiwan.Unfortunately,this resulted in a catastrophic landslide in Hsiaolin Village,Taiwan.Meanwhile,large amounts of landslides were formed in the Jiaopu Stream watershed near the southeast part of the Hsiaolin Village.The Hsiaolin Village access road(Provincial Highway No.21 and Bridge No.8) was completely destroyed by the landslide and consequent debris flow.The major scope of this study is to apply a debris flow model to simulate the disaster caused by the debris flow that occurred in the Jiaopu Stream during Typhoon Morakot.According to the interviews with local residents,this study applied the destruction time of Bridge No.8 and Chen's house to verify the numerical debris flow model.By the spatial rainfall distributions information,the numerical simulations of the debris flow are conducted in two stages.In the first stage(before the landslide-dam failure),the elevation of the debris flow and the corresponding potential damages toward residential properties were investigated.In the second stage(after the landslidedam failure),comparisons of simulation results between the longitudinal and cross profiles of the Jiaopu Stream were performed using topographic maps and satellite imagery.In summary,applications of the adopted numerical debris flow model have shown positive impact on supporting better understanding of the occurrence and movement of debris flow processes.

Influence of Potential Evapotranspiration on the Water Balance of Sugarcane Fields in Maui, Hawaii

The year-long warm temperatures and other climatic characteristics of the Pacific Ocean Islands have made Hawaii an optimum place for growing sugarcane;however, irrigation is essential to satisfy the large water demand of sugarcane. Under the Hawaiian tropical weather, actual evapotranspiration (AET) is the primary mechanism by which water is removed from natural and agricultural systems. The Hawaiian Commercial and Sugar Company (HC&S), the largest sugarcane grower of the Hawaiian Islands, has developed a locally optimized AET equation for the purpose of water management on its 184.3 km2 sugarcane plantation on the Island of Maui. In this paper, in order to assess the influence of AET on the hydrological water balance of the HC&S’ sugarcane cropping system, the performance of the HC&S method was compared with three physically-based methods: Penman-Monteith, Priestley-Taylor, and Hargreaves, as well as, to a set of historical pan evaporation data. A Soil and Water Assessment Tool (SWAT) project was setup to estimate the water balance in two sugarcane fields: a windy lowland field and a rocky highland field on a hill slope. Under Hawaiian weather conditions, wind speed was found to be the most influential climatic parameter over potential evapotranspiration (PET);therefore, the results with both Hargreaves and Priestley-Taylor underpredicted PET by approximately 30%, presumably because these methods do not take wind speed into account. The HC&S method was demonstrated to be the most accurate PET method compared to the other commonly used PET equations, with less than 10% error. Of the annual total water supply of 3400 mm, AET accounted for 75% - 80% of the total water consumption. These findings can be used to improve the irrigation efficiency as well as other management scenarios to optimize water use on the Island of Maui.

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratorysimulated rainfall events

Soil erosion,one of the most serious environmental concerns,might remove topsoil and essential element from terrestrial land.However,few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss.Therefore,this study investigated the effects of surface coverage rates(83%,67%,50%,33%,17%and 0%)and two positions(up-and downslope)on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls(R1-R6).These results showed that the sediment concentrations with 33%(R4)and 17%(R5)coverage downslope were significantly lower than those with coverage upslope,whereas there was no significant difference between the runoff rates of the two slopes.Thus,surface coverage at different positions induced two soil erosion regimes(deposition-and transport-dominated processes).Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff.The DON contributed to a substantial amount of soil nitrogen loss,which accounted approximately 81%of the organic form.The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes.The DOC is significantly correlated with Rr for transport-dominated processes.These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form.It is concluded that erosion/covered zones altered by surface coverage could produce transport-and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss.In addition,these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.

Uncertainty analysis for integrated water system simulations using GLUE with different acceptability thresholds

Integrated water quantity and quality simulations have become a popular tool in investigations on global water crisis.For integrated and complex models,conventional uncertainty estimations focus on the uncertainties of individual modules,e.g.,module parameters and structures,and do not consider the uncertainties propagated from interconnected modules.Therefore,this study investigated all the uncertainties of integrated water system simulations using the GLUE(i.e.,generalized likelihood uncertainty estimation)method,including uncertainties associated with individual modules,propagated uncertainties associated with interconnected modules,and their combinations.The changes in both acceptability thresholds of GLUE and the uncertainty estimation results were also investigated for different fixed percentages of total number of iterations(100000).Water quantity and quality variables(i.e.,runoff and ammonium nitrogen)were selected for the case study.The results showed that module uncertainty did not affect the runoff simulation performance,but remarkably weakened the water quality responses as the fixed percentage increased during calibration and validation periods.The propagated uncertainty from hydrological modules could not be ignored for water quality simulations,particularly during validation.The combination of module and propagated uncertainties further weakened the water quality simulation performance.The uncertainty intervals became wider owing to an increase in the fixed percentages and introduction of more uncertainty sources.Moreover,the acceptability threshold had a negative nonlinear relationship with the fixed percentage.The fixed percentages(20.0%-30.0%)were proposed as the acceptability thresholds owing to the satisfactory simulation performance and noticeably reduced uncertainty intervals they produced.This study provided methodological foundations for estimating multiple uncertainty sources of integrated water system models.