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1.
Climatic changes and elevated atmospheric CO2 concentrations will affect crop growth and production in the near future. Rising CO2 concentration is a novel environmental aspect that should be considered when projections for future agricultural productivity are made. In addition to a reducing effect on stomatal conductance and crop transpiration, elevated CO2 concentration can stimulate crop production. The magnitude of this stimulatory effect (‘CO2 fertilization’) is subject of discussion. In this study, different calculation procedures of the generic crop model AquaCrop based on a foregoing theoretical framework and a meta-analysis of field responses, respectively, were evaluated against experimental data of free air CO2 enrichment (FACE) environments. A flexible response of the water productivity parameter of the model to CO2 concentration was introduced as the best option to consider crop sink strength and responsiveness to CO2. By varying the response factor, differences in crop sink capacity and trends in breeding and management, which alter crop responsiveness, can be addressed. Projections of maize (Zea mays L.) and potato (Solanum tuberosum L.) production reflecting the differences in responsiveness were simulated for future time horizons when elevated CO2 concentrations and climatic changes are expected. Variation in future yield potential associated with sink strength could be as high as 27% of the total production. Thus, taking into account crop sink strength and variation in responsiveness is equally relevant to considering climatic changes and elevated CO2 concentration when assessing future crop production. Indicative values representing the crop responsiveness to elevated CO2 concentration were proposed for all crops currently available in the database of AquaCrop as a first step in reducing part of the uncertainty involved in modeling future agricultural production. 相似文献
2.
da Costa Eline Nayara Dantas de Souza Jéssica Carneiro Pereira Marilane Andrade de Souza Marcelo F. Landim de Souza Weber F. Landim da Silva Daniela Mariano Lopes 《Agroforestry Systems》2021,95(8):1647-1659
Agroforestry Systems - Inland waters such as streams that receive carbon from terrestrial landscapes usually have a net heterotrophic metabolism and emit significant amounts of CO2 to the... 相似文献
3.
Tolstoy E 《Science (New York, N.Y.)》2011,333(6039):176-178
Individual low-mass stars have very long lives, comparable to the age of the universe, and can thus be used to probe ancient star formation. At present, such stars can be identified and studied only in the Milky Way and in the very closest of our neighboring galaxies, which are predominantly small dwarf galaxies. These nearby ancient stars are a fossil record that can provide detailed information about the physical processes that dominated the epoch of galaxy formation and subsequent evolution. 相似文献
4.
Seasonal changes in nutritional status and reproductive performance of Zebu cows kept under a traditional agro-pastoral system in Tanzania 总被引：1，自引：1，他引：0
Kanuya NL Matiko MK Nkya R Bittegeko SB Mgasa MN Reksen O Ropstad E 《Tropical animal health and production》2006,38(6):511-519
The objectives of this study were to assess changes in nutritional status/body condition score, percentage pregnancy and calving
rate in Zebu cows and to establish the relationship between body condition score loss and postpartum interval to resumption
of ovarian activity. A total of 198 cows and postpubertal heifers of the Tanzanian Shorthorn Zebu kept under a traditional
management system were randomly selected from 200 smallholder herds. Factors investigated during bi-weekly visits include
body condition score (BCS), heart-girth circumference, milk yield and reproductive status of the animals, pregnancy/non-pregnancy
and cyclicity/non-cyclicity. Local weather conditions and dates of occurrence of other reproductive events such as calving
were also recorded. Calvings occurred all year round but with a strong seasonal distribution characterized by annual peaks
observed between April and July. The annual calving pattern was closely related to rainfall, with peak precipitation occurring
a few months before peak calving. The overall percentage pregnancy varied from 30% to 50% throughout the year. Postpartum
cows exhibited minimum mean BCS and heart-girth circumference 12–14 weeks after calving, and cows with BCS loss >1 point exhibited
the longest time interval from calving to onset of ovarian activity. 相似文献
5.
Nkya R Kessy BM Lyimo ZC Msangi BS Turuka F Mtenga K 《Tropical animal health and production》2007,39(8):627-636
Twenty five smallholder dairy farmers and other stakeholders, through a Participatory Rural Appraisal in three wards of the
Tanga township of north east coastal Tanzania, ranked their perceived constraints in descending order of importance: Low milk
price and marketing, feed shortage in the dry season, poor management, low animal productivity, poor reproductive performance
and diseases. Tick borne diseases were reported on a majority of farms. An Economic Opportunity Survey revealed wide ranges
in management indices and improvement in annual milk production, age at first calving and lactation length to represent the
best potential for gain. Performance generally was below locally set targets. Farmers spent on average in the three wards
between 39% and 77% of income from milk on feed costs yearly. Interventions were instituted emphasising those that farmers
could afford immediately. They included farmer training, dry season feed supplementation, tick control, improvement of animal
shed/house cleanliness and the formation of a cooperative for milk marketing. Partial budgeting is being used to monitor success.
Follow-up meetings and regular visits to farms by field officers are disseminating information on outcomes to encourage farmers
to continue with interventions and spread useful knowledge to friends and neighbours. 相似文献
6.
Lyimo ZC Nkya R Schoonman L van Eerdenburg FJ 《Tropical animal health and production》2004,36(3):269-279
The objective of this study was to monitor the reproductive performance of dairy cows in smallholder farms under the Tanga Dairy Development Project (TDDP). The findings can be used to improve reproductive efficiency. Dates of oestrus, artificial insemination (AI) or service by bull and calving were recorded, and pregnancy was diagnosed by rectal palpation. Daily milk yields, monthly body condition score (BCS) measured on the scale of 1-9, feed availability, calf rearing, and diseases were also recorded. Milk progesterone (P4) concentration was measured by radioimmunoassay (RIA) in 1327 sequential samples collected between day 15 and 120 in 46 post-partum Zebu x Friesian crossbred dairy cows. The mean interval from calving to first P4 rise above 2 nmol/L (cyclicity) was 66.1 +/- 6.8 days. Resumption of ovarian activity postpartum was early (< 60 days) in 45%, and late (> 60 days) in 55% of the cows. In about 45% of the cows the first post-partum ovarian cycles were short (< 14 days) and had low P4 concentrations. Oestrus was missed once or several times in 34.7% of the cows, most likely indicating poor oestrus detection, silent oestrus, or farmers deliberately not taking or reporting their cows for insemination. The mean interval to conception was within 130 days postpartum. Average daily milk production was 5.7 +/- 2.2 L and the mean BCS Was 3.1 +/- 1.3. Both milk production and BCS had no clear influence on the measured reproduction parameters. Clinical uterine involution was complete within 29 +/- 2.6 days of calving in the majority of cows. Progesterone profiles and rectal palpation revealed various causes of infertility, which included anoestrus, silent oestrus, irregular oestrous cycles, and infection of the uterus. The major causes of animal culling, death, slaughter or sales include tick-borne diseases and trypanosomiasis, which have high prevalences in the area, infertility, low productivity and old age. Greater attention should be focused on reproduction and its interaction with nutrition and disease control. 相似文献
7.
Nicolas Vallarino Eline Wydooghe Bart van Goethem 《Reproduction in domestic animals》2020,55(9):1172-1179
Disorders of sexual development (DSD) in dogs involve most commonly an XX sex reversal syndrome, treated conventionally by gonadohysterectomy. The objective of the present case series is to describe the surgical treatment and long-term follow-up of dogs undergoing laparoscopic gonadectomy without hysterectomy for treatment of ovotesticular DSD. Six female dogs clinically diagnosed with DSD were retrospectively included in the study when laparoscopic gonadectomy was performed and histology confirmed the presence of abnormal gonads. The dogs were evaluated by ultrasound after 6 months, and owners were contacted by phone for the long-term reevaluation. Laparoscopic gonadectomy was performed using 2- or 3-portal midline techniques with 3- and/or 5-mm instruments. Additional procedures were performed in 5 dogs, including os clitoris removal in 4 dogs and vulvoplasty in 1 dog. Histological analysis of the gonads reported 11 ovotestes and 1 testis. No major or minor complications occurred perioperatively. Ultrasonographic reevaluation was performed in 5/6 dogs and the remaining abdominal genital system was considered normal. Median long-term follow-up was 617 days (range, 265–1597) with none of the dogs having any symptom related to DSD. Therefore, laparoscopic gonadectomy is a valid alternative for dogs with ovotesticular DSD and is less invasive than conventional open techniques. Removal of the gonads avoids future development of hormone-related diseases of the remaining genital tract. 相似文献
8.
Phiri EC Nkya R Pereka AE Mgasa MN Larsen T 《Tropical animal health and production》2007,39(5):317-323
The effects of calcium (Ca), phosphorus (P) and zinc (Zn) supplementation on reproductive performance of grazing dairy cows
was studied. Forty-eight cows in their first to third parity were allocated to eight groups of 6 animals each, based on stage
of lactation and milk yield. Groups 1 (control), 2 (Ca), 3 (P) and 4 (Zn) received, respectively, no mineral supplement, 10 g
Ca, 8 g P and 400 mg Zn. The rest of the groups received a combination of Ca/P, Ca/Zn, P/Zn or Ca/P/Zn. Animals were drenched
daily. Ovarian activity was determined by progesterone concentrations in milk. Prepartum body condition score (BCS) measured
using scale 1–5 was 2.5–3.5. Reproductive problems were observed in all groups except that supplemented with Ca. Cows supplemented
with Ca, P, Ca/P, Ca/Zn and Ca/P/Zn had significantly (p < 0.05) shorter interval (30 days) from calving to resumption of oestrus as compared to control (69 days). Intervals from
calving to conception and between calvings did not differ significantly between groups (p > 0.05), but were shorter in Ca-supplemented cows. Furthermore, cows in groups 2 and 3 needed an average of 2 services per
conception against 3 for cows in other groups. Hence, supplementation with Ca, P and Zn of deficient dairy cows appears to
improve reproductive performance. 相似文献
9.
Siwa Ernest Nkya Martin Hagai Japhet Joel Kashaigili 《East African Agricultural and Forestry Journal》2017,82(2-4):188-200
The study focused on contributing to the spatial knowledge of the impacts of land cover changes on beef cattle production under a changing climate in rangelands of the Lake Victoria Basin (LVB), so as to establish a strategy for improving beef cattle production in the area. We used supervised classification of satellite imagery to analyze land cover changes between the years 1980–2000 and 2000–2010. Results revealed that for the periods 1980–2000 and 2000–2010, settlements increased by 1% and 8%, and cultivated area increased by 0.58% and 0.30%, respectively. Riverine vegetation declined by 0.26% and increased by 0.16%, and woodlands declined by 6% and 13% respectively. The trend of beef cattle numbers against rainfall and pasture area (riverine vegetation and woodland) over the study period 1980–2010 showed a non-significant trend of increasing rainfall in the study area. In Ilemela District, pasture area and beef cattle numbers declined by 33% and 4% respectively. In Magu District, beef cattle numbers increased by 64% and pasture area declined by 84%. This implies that the effect of urbanization is more severe in Ilemela than in Magu District. Land use planning, enhancing of mixed crop-livestock farming systems, intensification of livestock practices, forage conservation, planting of fodder trees, and matching of cattle numbers with pasture availability are recommended. In addition, education is needed on effective cattle farming as a strategy for improving beef cattle production in the face of land cover changes due to climate variability in the area. 相似文献
10.
The history of dam construction in Zimbabwe dates back to the 1920s and since then over 7,000 small dams have been constructed countrywide. Small dams are multipurpose structures used for improving rural livelihoods. The multipurpose nature of these dams has largely gone unquantified in terms of importance of the uses to the community and influence of management practises. The current study made use of a questionnaire among small dam users, key informant interviews, secondary data and observation on four communal dams in the Limpopo basin to establish the uses, volume of water abstracted and water productivity for some uses and the interrelationship between various organisations and the community in the management of small dams. Uses on all dams in order of importance were livestock watering, domestic use, irrigation, fishing, brick making, and collection of reeds used for roofing. Livestock consume on average over 70% of water for consumptive uses. Water productivity in terms of yield per volume unit of water used ranged from 0.025 kg m?3 for vegetables to 7,575 kg m?3 for bricks, and monetary values per volume unit of water used were Z$ 389,434 m?3 for brick making and Z$ 1,874 m?3 for irrigation. Traditional leadership and the community are pivotal in the management of the small dams, with some organisations giving technical, financial and input assistance. The management and conservation of small dams needs to be well coordinated between the communities, NGOs and government if the full benefits of these national resources are to be realised in the long term. 相似文献