The aim of the present investigation was to study the effect of white clover (var. Milka and Donna), red clover (var. Fanny) and ryegrass (var. Tove) undersown in winter wheat on a succeeding oat crop. Under the climatic conditions prevailing in Sweden, growing a catch crop after winter cereals is of particular interest because the latter are usually followed by a spring sown crop, leaving the ground bare during autumn and winter. Field trials were carried out during three growing seasons in an integrated farming system and for one year in an organic farming system. Competition from the dense wheat crop in the integrated farming system had a negative effect on the undersown species, and at harvest of the wheat they showed quite poor growth in all three years, with nitrogen contents under 5 kg ha?1. No significant yield increase was measured without added nitrogen when the averages for all three years were calculated. On average, the grain yields were improved by 750 kg ha?1 (14% moisture content) for the treatments with undersown clover for all three years when 90 kg N ha?1 were added. The experiment within the organic system showed a different pattern with a better development of the undersown clover species, with nitrogen contents approximately 25 kg ha?1 and an improvement in oat grain yield, from around 2?000 kg ha?1 for the control to almost 3?500 kg ha?1 with clover undersown the previous year. 相似文献
Crop tolerance to land submergence is an important criterion for designing a surface drainage system for agricultural lands. This paper collates the available data from various places in India related to the studies on the submergence tolerance of crops. The paper hypothesizes that a piecewise linear model could be used to describe crop response to land submergence. According to this hypothesis, there would be no yield decline for a few initial days of submergence. If submergence continues beyond this period then there would be linear decline in yield. The unknown parameters in the model are: optimum yield, threshold time and the slope which represents the per cent yield reduction per day of additional submergence beyond the threshold.Data in respect of wheat, pigeon peas, cowpeas, pearlmillet, maize and groundnuts indicate that the model describes the data well, although in many cases the threshold is 0.0. The yield reduction varies from 5.3 to 23.2% for each day of submergence beyond the threshold. It appears that to allow for more than 1–2 days of submergence will result in more than 10% reducation in yield of dryfoot crops. For the maize crop, the seedling stage is the most sensitive stage followed by the silking stage. The grain formation stage is the least sensitive, although even at this stage the threshold is 0.0 and yield reduction is 9.3% for each day of submergence beyond the threshold. The data for 9 test crops from Texas and Venezuela were well described by the model. It is concluded that the piecewise linear model is a useful tool for describing submergence tolerance of crops and for working out surface drainage requirements for a given level of yield reduction. Frequency analysis of the daily rainfall data from some selected locations indicates that there is every likelihood of submergence at most of the stations. It is suggested that there is an urgent need for developing wet farming techniques analogous to dry farming techniques. 相似文献
This study was conducted to determine relationships between biotic and abiotic factors and to generate information needed to improve the management of site-specific farming (SSF). The effects of water (80% evapotranspiration (ET) and 50% ET), hybrid (drought-tolerant and -susceptible), elevation, soil texture, soil NO3--N, soil pH, and greenbugs (Schizaphis graminum) (Gb) on sorghum grain yield were investigated at Halfway, TX on geo-referenced locations on a 30-m grid in 1997, 1998, and 1999. Grain yields were influenced by interrelationships among many factors. Grain yields were consistently high under 80% ET treatment and in the upper slopes where the clay and silt fractions of the soil were high. Soil NO3--N, rainfall, hybrid, and Gb effects on grain yields were seasonally unstable. Soil NO3--N increased grain yield when water was abundant and depressed grain yields when water was limiting. Plant density effects on grain yield were confounded with hybrid responses to drought and Gb infestation. Managing seasonally unstable factors is a major challenge for farmers and better ways to monitor crop growth and diagnose causes of poor plant growth are needed. To improve the management of SSF, effects of the relationships between biotic and abiotic factors on crop yield must be integrated and evaluated as a system. Based on our study, information on seasonally stable factors like elevation and soil texture is useful in identifying management zones for water and fertilizer application. Water and fertilizers management should be complemented by in-season management of seasonally unstable factors like soil NO3--N, rainfall, hybrid, and Gb effects on grain yield. 相似文献
Farmers' relationship with nature isdetermined by the significance of agriculturefor human beings. When agriculture is definedas human activity that uses renewable naturalresources and aims to produce usable food andfiber products, agriculture is explicitlydefined as production. Farmers' relationshipwith nature is based on the principle ofproduction. This article discusses thecontradiction between the peasant values ofprotection of nature that many farmers inFinland still have and the environmental harmtheir production-oriented farming style causes.When farmers interpret their farming practicesas harmonious co-operation with nature, it isdifficult for them to see the polluting effectsof their work. Paul B. Thompson's suggestionthat three religious–philosophical doctrines(hard work, the doctrine of grace, and the mythof garden) have made it easy for farmers toadopt productionist farming strategy is used asa framework to interpret farmers' narrativesconcerning their relationship with nature. Theresearch is qualitative and biographical. Thedata include life stories and biographicaltexts farmers wrote for a competition in1997. 相似文献
In response to rapidly growing interest in precision farming, universities and others have developed numerous educational programs. Many of these events are multi-day conferences and workshops as these venues provide the time necessary for attendees to learn about the many technologies, analysis approaches, and management strategies that make up precision farming. The Washington State University Western Precision Agriculture Conference, the Assiniboine Community College Precision Agriculture Conference and the University of Nebraska–Lincoln Crop Modeling for Environment-Specific Management Workshop exemplify these types of educational programs. The Western Precision Agriculture Conference uses a traditional format where the audience primarily listens to presentations. The Assiniboine Community College Precision Agriculture Conference provides a mixture of presentations and hands-on sessions where attendees actually use precision farming tools or develop site-specific management plans. Finally, those who attend the University of Nebraska–Lincoln Crop Modeling for Environment-Specific Management Workshop complete exercises related to each topic and presentation. Because a conference or workshop brings many experts together for a short period of time, organizers of all three events have tried to capture conference content for later use in other educational programs. Their approaches to this include videotaping interviews of conference speakers and assembling software and data used during the conference on compact disk. Given the multidisciplinary nature of precision farming, conferences and workshops that utilize multiple expert presenters such as those discussed in this paper are among the best sources of precision farming education. 相似文献
以杂交粳稻(常优2号、常优5号、甬优8号)和常规粳稻(淮稻5号、南粳46、南粳5055)为试材,比较研究了有机和常规栽培方式对两种类型粳稻的产量和品质的影响,探索了有机栽培条件下杂交粳稻实现稳产优质的可能性。结果表明,有机栽培杂交、常规粳稻平均产量分别为8.11 t hm–2和6.29 t hm–2,前者比后者高28.93%。有机栽培杂交粳稻的群体总茎蘖数低于常规粳稻,但成穗率较常规粳稻增加了6.5个百分点。两种类型水稻叶面积指数和光合势在各生育期均表现为有机栽培常规栽培,但有机栽培杂交粳稻叶面积指数和光合势降幅较小。有机栽培条件下,杂交粳稻生育后期平均群体生长率是常规粳稻1.29倍,干物质积累比例高出8.81个百分点。有机栽培略微降低了杂交粳稻的加工品质,但显著改善了外观品质,提高胶稠度、降低直链淀粉含量,对蛋白质含量影响较小,总体上改善了蒸煮食味品质。有机栽培下杂交粳稻产量优势明显且有较好的品质性状,在有机稻米产业发展中具有独特的应用价值。 相似文献
Wheat and barley yields from three farms in the Ebro river valley are shown to be strongly dependent on seasonal rainfall, particularly that during November-January and March-May of the cropping season. In the driest farm, in Monegrillo, Zaragoza province (seasonal rainfall, 251 mm), yields increased by c. 5.9 (wheat) and 9.4 (barley) kg ha−1 per mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canós and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha−1, respectively, per mm of extra rain in the cropping season, taken as September to May inclusive.
In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared to minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), raising the average yields of crops greater than 300 kg ha−1 to 1222 and 1522 kg ha−1, respectively. Agronomic practices in Monegrillo during the fallow should focus on means of increasing the proportion of the rain stored in the profile during the fallow. At all three locations, decreasing water evaporation from the soil during the cropping season would likely benefit yield. 相似文献