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1.
The standardized ASCE Penman–Monteith and FAO-56 equations were used to estimate reference evapotranspiration (ET0) using estimated and measured net radiation (Rn) and soil heat flux (G), based on hourly and daily meteorological data. The estimates were evaluated against lysimeter measurements. The results indicate that using measured or estimated values of Rn and G can have significant effect on the accuracy of the ET0 estimations, especially when calculations were made on an hourly basis. The FAO-56 version performed very well during the irrigation season on a daily basis. The use of measured Rn and G did not improve ET0 estimation on a daily basis, therefore, the use of estimated Rn and G appears to be dependable when calculations are based on 24-h weather data. When daily ET0 was calculated from hourly estimations, the results were different depending on the version used. The ASCE version was more accurate, especially when Rn and G were measured. Therefore, measurement of Rn and G may have potential to improve estimation only when daily ET0 is calculated from hourly estimations. The PM FAO-56 version was always a little less accurate than the ASCE version. For hourly calculations, using a constant surface resistance (as in FAO-56 version), the PM method underpredicted for high evaporative demand and vice versa. The ASCE version performed better than PM FAO-56 version when Rn and G were measured and estimated. Therefore, ASCE version tended to provide quite accurate values of hourly ET0, even using estimated values of Rn and G. As conclusion, the methods proposed by FAO-56 for estimating Rn and G tended to produce accurate estimates for daily and hourly ET0 under semiarid conditions and can be used with some degree of confidence for estimating ET0. In addition, results suggest that the ASCE standardized equation on an hourly basis improved the accuracy of ET0 estimation with respect to the FAO-56 version. 相似文献
2.
U. Keese C. Nitsche S. Knappe U. Waldschmidt 《Archives of Agronomy and Soil Science》2013,59(3):209-231
Zur Quantifizierung möglicher Veränderungen zwischen langjährig genutzten Lysimetern und ihren Herkunftsflächen wurden ausgewählte bodenphysikalische Parameter ermittelt und eine erste Interpretation der angetroffenen Unterschiede zwischen Lysimeter und Herkunftsfläche vorgenommen. Zur Ermittlung bodenhydraulischer Kenngrößen können unterschiedliche Verfahren eingesetzt werden. So wurden Saugspannungs‐Sättigungs‐Funktionen (pF‐Kurven) mittels AMHYP‐Anlage und mit der Verfahrenskombination: Sandbett‐Kaolinbett‐Drucktopfapparatur erstellt. Die dabei festgestellten deutlichen Abweichungen geben Anlaß zur Überprüfung der bisher verwendeten Verfahren, der damit ermittelten Meßwerte und deren Interpretation. 相似文献
3.
在着重介绍研制“非称量测渗仪”目的意义，国内外研究现状，研制发展过程的同时，简要地介绍了利用“非称量测渗仪”进行研究的内容，方法和所得的主要成果。 相似文献
4.
Carbon,nitrogen and phosphorus leaching after site preparation at a boreal forest clear-cut area 总被引：1，自引：0，他引：1
Clear-cutting followed by mechanical site preparation is the major disturbance influencing nutrient and water fluxes in Fennoscandian boreal forests. The effects of soil harrowing on the fluxes of dissolved organic carbon (DOC), dissolved nitrogen compounds (organic N, NH4+ and NO3−) and water soluble phosphorus (PO43−) through a podzolic soil were studied in a clear-cut in eastern Finland for 5 years. The old, mixed coniferous stand was clear-cut and stem only harvested in 1996 followed by soil harrowing in 1998 and planting in June 1999. Zero-tension lysimeters were used to collect soil water from below different soil horizons in the three types of microsites that resulted from site preparation treatment: low ridges (25% of clear-cut area), shallow furrows (30%) and the undisturbed soil (45%). After soil harrowing, the leaching of DOC, N and P from below the B-horizon increased compared to pre-treatment levels. However, the increases were short-lasting; 1–2 years for inorganic N and P, and 5 years for DOC and organic N. The highest concentrations were associated with the ridges and lowest with the furrows, reflecting the differences in amount of organic matter present in each microsite type and, for N, to enhanced mineralization and nitrification. Leaching from below the B-horizon over the 5 years following soil harrowing for the whole clear-cut area was 36.5 kg ha−1 for DOC, 0.88 kg ha−1 for NH4-N, 0.46 kg ha−1 for NO3-N, 1.24 kg ha−1 for organic N and 0.09 kg ha−1 for PO4-P. Site preparation increased temporarily the risk for nutrient leaching into watercourses and groundwater from the clear-cut area but soil fertility was not affected since the leached amounts remained small. The main reasons for the observed low leaching values were the rapid recovery of ground vegetation and low N deposition loads. 相似文献
5.
百喜草人工植被对坡面径流的影响 总被引：3，自引：0，他引：3
为研究百喜草(Paspalum notatum Flugge)及其凋落物水源涵养作用,采用土壤水分渗漏装置进行试验,得到不同处理的地表和土壤径流深。结果表明:不同处理小区的径流组成有很大差异,A(百喜草覆盖处理小区)、B(百喜草敷盖处理小区)、C(裸露对照处理小区)各处理的总径流深分别为1245.24、1453.81和1383.23mm,其中,地表径流深分别为24.46、50.2和592.07 mm,土壤径流深分别为1220.78、1403.61和791.16mm;A、B、C各处理的地表径流深与降雨量拟合最优经验方程均为二次抛物线型方程,相关系数分别为0.933、0.861和0.810,方程均达极显著性相关;方差分析结果显示,不同处理的地表径流深存在显著性差异。 相似文献
6.
太湖地区稻麦轮作农田氮素淋洗特点 总被引：37，自引：0，他引：37
通过排水采集器模拟试验研究了太湖地区不同施肥水平下农田N素淋洗特点。结果表明,N的渗漏损失以硝态氮（NO3^--N）为主,并发生在麦季,铵态氮（NH4^ -N)淋洗量则很少,NO3^--N的量占渗漏液总N量的43%-72%,浓度为20-110mg/kg;渗漏水中N的含量与土壤N的淋洗量随施肥量的增加而增加,麦季土壤中NO3^--N肥量的3.7%-12.2%;与纯化肥处理比较,化肥 猪粪处理增加了农田N的淋失,化肥 秸秆处理减少了土壤中N的淋失,与麦田渗漏水相比较,稻田渗漏水除水稻生长早期的部分样品外,NO3^--N和NH4^ -N含量均很低,分别在1mg/kg和0.5mg/kg以下。 相似文献
7.
Monique Masche 《Archives of Agronomy and Soil Science》2013,59(2):211-220
Pasture with burdening on peat-bog done four times a year has more positive effects on the water balance than twice grassland use. The saving of water that has been determined by lysimeters evokes no positive effects on the N-, P-, K- or Ca-balance. Due to the lower depth of the plant roots under lowland bog used for pasture more nutrients were leached into the ground water. The soil compression leads to anaerobic conditions. Therefore the phosphorus becomes more mobile and migrates into the outlet. The effect on the peat mineralization and the nutrient balances was not as clear as assumes, because other parameters like the combination of the vegetation formation and the age of the plants also had a strong influence on the factor. The younger plants from the pastures have show higher nutrient contents so that the nutrient export is higher and the balance becomes more negative. 相似文献
8.
Gerhart Mundel 《Archives of Agronomy and Soil Science》2013,59(3):235-246
Insgesamt wurden 12 hydromorphe Böden 15 ... 19 Jahre kontinuierlich auf den Kalziumaustrag in Grundwasserlysimetern untersucht. Folgende Bodenfaktoren wurden im Zusammenhang mit dem Ca‐Austrag geprüft: absoluter Kalziumgehalt, absoluter Humusgehalt, Körnung allgemein, Mächtigkeit lehmiger Horizonte, absoluter Tongehalt im Bodenkörper und pH‐Wert. Unter den untersuchten Bodenfaktoren üben Kalzium‐ und Humusgehalt den stärksten Einfluß aus. Doch sind alle Zusammenhänge lose, da die aktuellen Witterungsverläufe einen viel größeren Einfluß auf den Kalziumaustrag haben. Keinen Einfluß auf den Ca‐Austrag haben die Bewirtschaftungsmaßnahmen, wenn man von vorausgegangenen Entwässerungen absieht. Die höchsten Austräge weisen Eutric Histosols und die geringsten ein Gleyic Podzol auf. 相似文献
9.
Gerhart Mundel 《Archives of Agronomy and Soil Science》2013,59(6):467-481
In Grundwasserlysimetern wurden 12 verschiedene hydromorphe Böden 12–17 Jahre auf den Kalziumaustrag in das Grundwasser untersucht. Auf Grund der langen Untersuchungszeiten mit ihren wechselnden Witterungsverläufen schwanken die Ca‐Austräge bei allen Böden bedeutsam, wobei die größten Schwankungen bei Niedermoor‐ und Anmoorböden zu verzeichnen sind. Erwartungsgemäß erbrachte die Sickerwasserrate den engsten Zusammenhang zum Ca‐Austrag (B = 0,47–0,84). Die mittleren Ca‐Konzentrationen reichen von 100 mg.l?1 bei einer Gley‐Rosterde bis zu 300 mg.r?1 bei einem Niedermoor. Ein Einfluß der Evapotranspiration auf den Ca‐Austrag ließ sich nicht feststellen. 相似文献
10.
D.P.C. Stewart K. C. Cameron I. S. Cornforth B. E. Main 《Biology and Fertility of Soils》2000,31(2):128-133
The release of SO4
2–-S, K+, Ca2+ and Mg2+ from soil amended with spent mushroom compost (SMC), a byproduct of mushroom production, was measured in leachate from field
lysimeters for 30 weeks. Rates of application were 0 and 80 t ha–1 moist SMC. The SMC contained 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is SO4
2–-S), and has a C : S ratio of 26. The break-through curves of ion leaching were polymodal indicating the preservation of soil
structure in the lysimeters and its influence on leaching. SO4
2–-S release from SMC was rapid (first-order exponential) and was very similar to the release from a laboratory incubation.
The release of K+, Ca2+ and Mg2+ was described using first/zero-order models which were also used to describe their release in the laboratory. The rate and
amount of Ca2+ release was similar in the field and laboratory, but the amount of K+ (and to a lesser extent Mg2+) release was less in the field than in the laboratory. Recoveries of SMC applied nutrients in leachate were 80% of S (263 kg
ha–1), 3% of K (14 kg ha–1), 16% of Ca (284 kg ha–1) and 37% of Mg (40 kg ha–1). Little if any S was mineralised. Using SMC could provide plants with S, K, Ca and Mg but there is potential for SO4
2–-S losses via leaching.
Received: 7 April 1999 相似文献