Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK     

A. Bhogal  A. Bhogal  M.A. Shepherd  D.J. Hatch  L. Brown  S.C. Jarvis 《Soil Use and Management》2001,17(3):163-172

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.  相似文献   

Economic Assessment of Alternative Aquaculture Aeration Strategies     

Carole R. Engle  Upton Hatch 《Journal of the World Aquaculture Society》1988,19(2):85-96

Oxygen depletion is a serious problem for the catfish industry, especially as producers attempt to increase their production intensity. Aeration, either emergency or continuous, is the most common method used to address oxygen depletion.
A risk-programming model using Target MOTAD methodology was developed to study the aquacultural producer's aeration decision-making process. Effects of stocking rate, aeration yield response and availability of labor, capital and electricity on the selection of aeration strategy were analyzed.
Continuous aeration with electric paddlewheels was most often selected as the best aeration strategy. However, as farmers become increasingly concerned with financial risk, they apply continuous aeration with pump sprayers first, then no aeration and lastly emergency aeration with tractor-powered paddlewheels. Emergency aeration was only used when: 1) electricity was not available and the producer desired a highly conservative financial strategy, and 2) the relative efficiency of continuous aeration in the field was dramatically reduced from experimental results.  相似文献   

Use of thiols and thiosulfate for treatment of experimentally induced acute arsenite toxicosis in cattle.     

R C Hatch  J D Clark  A V Jain 《American journal of veterinary research》1978,39(9):1411-1414

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Concurrent measurements of net mineralization, nitrification, denitrification and leaching from field incubated soil cores   总被引：5，自引：0，他引：5  

D. J. Hatch  S. C. Jarvis  R. J. Parkinson 《Biology and Fertility of Soils》1998,26(4):323-330

An improved method is described for incubating intact soil cores in the field, which permits concurrent measurement of net mineralization, nitrification, denitrification and leaching. Cores were enclosed in PVC tubes with minimal disturbance to the physical state or to the natural cycles of wetting/drying, soil temperature and aeration during an incubation lasting 4–5 days. An example of the application of the method is given in which soils with contrasting drainage characteristics were compared. Over a 64-day experimental period, 58% of the mineralized nitrogen (N) in a freely drained soil was nitrified and 36% of the nitrate-N (NO₃ ^–-N) was denitrified. In a poorly drained soil, 72% of the mineralized N was nitrified and 63% of the NO₃ ^–-N was denitrified. In both soil types, 18% of the remaining NO₃ ^–-N was leached. Rates of nitrification were significantly correlated with net mineralization (r ²=0.41 and 0.52) and also closely correlated with denitrification (r ²=0.67 and 0.68) in the freely and poorly drained soils, respectively. Independent measurements of these processes, using alternative techniques (for the same period), compared favourably with measurements obtained with the improved incubation method. Adoption of this method has a number of advantages with respect to field net N mineralization, and also allows interpretation of the impact this may have on other N transformation processes. Received: 18 June 1997  相似文献   

Towards the development of a bioeconomic stocking model for the semi‐arid savanna of KwaZulu‐Natal     

G.P. Hatch  N.M. Tainton  G.F. Ortmann 《African Journal of Range and Forage Science》2013,30(2):67-71

Abstract

Rainfall variability is a major determinant of system dynamics and profitability of livestock enterprises in arid and semi‐arid environments. Range managers consequently require detailed information on the financial and ecological implications of various stocking strategies in order to formulate viable management systems. Data collected over seven seasons (1986–1993), from a series of extensive grazing trials in the semi‐arid savanna of KwaZulu‐Natal with cattle stocked at three rates (0.17, 0.23 and 0.30 LSU ha^?1) were used to develop a bioeconomic stocking model (LOWBEEF). The model comprised two biological sub‐models (BEEF and GRASS), and an integrated economic component. The BEEF sub‐model related seasonal live mass gain to stocking rate and rainfall. The GRASS sub‐model related residual herbage at the end of summer to summer stocking intensity, range condition (indexed as the sum of proportions of three key forage species, Themeda triandra, Panicum maximum and P. coloratum) and rainfall. The period over which supplementary feeding would be required to maintain cattle mass was related to residual summer herbage mass. The biological sub‐models were linked to an economic component model (ECON) to reflect the influence of various environmental and economic parameters on profitability.  相似文献   

Salivary gland neoplasia in the dog and cat: survival times and prognostic factors     

Hammer A  Getzy D  Ogilvie G  Upton M  Klausner J  Kisseberth WC 《Journal of the American Animal Hospital Association》2001,37(5):478-482

Twenty-four dogs and 30 cats with histopathologically confirmed salivary gland neoplasia were retrospectively reviewed in a multi-institutional study. The predominant presenting complaint for animals with salivary gland neoplasia was that of a mass being noted by the owner; other common complaints included halitosis, dysphagia, and exophthalmia. Siamese cats were overrepresented, indicating a possible breed predisposition. The most common histopathological type was simple adenocarcinoma. Cats had more advanced disease at diagnosis than did dogs, and clinical staging was prognostic in dogs. The median survival times for dogs and cats were 550 days and 516 days, respectively.  相似文献   

Effect of different levels of cane molasses on nitrogen and energy utilization in urea rations for steers   总被引：1，自引：0，他引：1  

C F Hatch  W M Beeson 《Journal of animal science》1972,35(4):854-858

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ASTRONOMICAL NOTES     

Upton W 《Science (New York, N.Y.)》1899,9(215):224-225

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Bilateral hydronephrosis secondary to endometriosis managed by endoscopic ureteral stent placement in a captive Guinea baboon (Papio papio)     

Dallwig RK  Langan JN  Hatch DA  Terio KA  Demitros C 《Journal of zoo and wildlife medicine》2011,42(4):747-750

Spontaneous endometriosis is an estrogen-dependent, progressive and painful disease that affects a variety of nonhuman primates, including several species of baboons (Papio sp.). This case documents multimodal management of severe endometriosis in a captive female baboon within a zoological institution. An 18-yr-old, intact female Guinea baboon (Papio papio) was found to have an enlarged uterus. Fifteen months post ovariohysterctomy, scarring associated with endometrial tissue resulted in ureteral strictures, bilateral hydronephrosis, and azotemia. Cystoscopic placement of bilateral ureteral stents with fluoroscopy was performed and resulted in short-term clinical improvement. The animal's condition declined and euthanasia was elected 4 mo after ureteral stent placement. Severe endometriosis with secondary inflammation resulting in bilateral hydroureter and hydronephrosis, as well as concurrent cystitis, ureteritis, and pyelonephritis were confirmed at necropsy. Despite possible complications, ureteral stents can be considered a useful therapeutic option in patients with ureteral disease.  相似文献   

Antagonism of ketamine anesthesia in cats by 4-aminopyridine and yohimbine   总被引：1，自引：0，他引：1  

R C Hatch  N H Booth  J V Kitzman  B M Wallner  J D Clark 《American journal of veterinary research》1983,44(3):417-423

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