| 1 | 作业质量监督、风险偏好与农户生产外包服务需求的环节异质性显示文摘近年来农业生产外包服务发展迅速,但各环节差异很大。本文分析作业质量监督和农户风险偏好等因素对生产外包服务需求环节异质性的影响。研究发现,生产外包服务存在一定的不确定性,风险规避程度较高的农户倾向于减少外包服务支出。分环节的研究表明,农户风险偏好程度显著影响植保、施肥和收割环节的需求,但对整地和播种环节的影响并不显著。此外,由于整地与收割环节相对容易实现机械化,农户对该环节的外包服务需求较大;而作业质量监督较难的特征在一定程度上抑制了农户对植保环节外包服务的需求。为了促进外包服务的全面发展,政府制定农业政策时应重视不同环节的技术特征差异,以提高机械化程度,进一步降低外包服务的不确定性,防范服务风险。 | 孙顶强 Misgina Asmelash 卢宇桐 刘明轩 | 2019 | 农业技术经济2019，，4： | 49 |
| 5 | The arbuscular mycorrhizal fungi status of selected tree nurseries in the Ethiopian highlands显示文摘We investigated the arbuscular mycorrhizal fungi(AMF)status of ten nurseries suitable for restoration of dry evergreen Afromontane forests in Ethiopia.We quantified AMF root colonization(RC)and spore abundance(SA)in seedlings of nine native tree species namely Acacia abyssinica Hochst.ex Benth.,Cordia africana Lam.,Dovyalis abyssinica(A.Rich.)Warb.,H agenia abyssinica J.F.Gmel.,Juniperus procera Hochst.ex Endl.,Millettia ferruginea(Hochst.)Baker,Olea europaea L.subsp.c uspidata(Wall.ex G.Don)Cif.,Podocarpus falcatus(Thunb.)R.Br.ex Mirb.and Prunus africana(Hook.f.)Kalkman.We used the ink and vinegar method to stain AMF in roots.RC levels ranged from 8.00 to 99.67%and were generally higher than the RC levels reported from other similar nurseries in Ethiopia.SA levels ranged from 1 to 25 spores g~(-1)and werecomparable with some reports from the field in Ethiopia but they were lower than levels reported by another similar study.RC was more affected by host species than nursery location,while the reverse was true for SA.The results also showed that nursery management could improve AMF status among seedlings.When all nursery tree species were considered,RC and SA levels were unrelated.No strong correlation existed between the nursery management variables considered and RC or SA.However,considering C.africana,J.procera and P.falcatus separately,RC-age(r_(s)=0.829,P=0.042)correlation for O.europaea and RC-pot diameter(r_(s)=0.820,P=0.046),RC-pot volume(r_(s)=0.928,P=0.008)and SA-age(r_(s)=0.943,P=0.005)correlations for C.africana,were significant,strong and positive.Generally,most of the tree species and particularly,early-mid successional tree species had sufficient AMF inoculum.Hence,only the mid-late successional tree species;J.procera,P.falcatus,and P.africana may require AMF inoculation,preferably,during filed planting.Based on our results,age and pot volume were identified to be important variables potentially affecting RC and SA.To better understand the effects of these and other nursery management variables,additional study is required.We demonstrated for the first time that black Hero ink is suitable for staining root AMF and can be used in future AMF research. | Fisseha Asmelash Tamrat Bekele Fassil Kebede Zerihun Belay | 2021 | Journal of Forestry Research2021，32，3： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员