Species relative dominance by basal area was assessed along an agro ecological gradient in the Mau Forest Complex (MFC). Trees were recorded per species and diameter at breast height (D1.3) for size class D1.3 ≥ 10 c...Species relative dominance by basal area was assessed along an agro ecological gradient in the Mau Forest Complex (MFC). Trees were recorded per species and diameter at breast height (D1.3) for size class D1.3 ≥ 10 cm in 60 quarter hectare plots distributed in 7 agro ecological zones (AEZ) namely LH1, LH2, LH3, LH4, UH0, UH1 and UH2. Basal area per species was used to calculate species relative dominance i.e. the proportion of basal area by a species to the total basal area of the AEZ. Species associations were analysed as the group of highly ranked species in each AEZ. Sorensons similarity index was used to calculate the proportion of similar species among AEZ. Analysis of variance compared basal area among AEZ and Tukey’s multiple comparison test used to identify specific AEZ with differences. Tabernaemontana stapfiana (Britten) was ranked first in LH1, UH1 and UH0 with relative dominance values of 22.66%, 22.89% and 30.73% respectively. It was however not recorded in any other AEZs. Dombeya goetzenii (K. Schum) occurred in 6 of the 7 AEZs but had moderate dominance values in each of the 6 AEZs. The sum of dominance values per species in all AEZs indicated no species mono-dominance and different species dominated at different AEZs. Co-dominance resulted in species associations like Tabernaemontana-Allophylus-Eke-bergia-Albizia in LH1, Juniperus-Dombeya-Casearia-Prunus in LH2, Acokanthera-Cussonia-Olea-Teclea in LH4 and Tabernaemontana-Syzygium-Podocarpus-Neoboutonia in UH1. Species richness was highest in UH1 and had the highest similarity indices with those of other AEZs. The UH1 had a species similarity of 67% with LH1, 63% with LH2 and 56% with LH4. However, species in the very humid zone UH0 differed with those of the drier lower highland zones (UH0 vs LH3 and vs LH4 = 31% and 37% respectively). Basal area differed significantly among AEZ ( = 3.76) showing that they differ in stocking levels. Tukeys test showed that high potential zones of LH1, LH2, UH0, UH1 did not differ and similarly the lower potent展开更多
This study was designed to use LiDAR data to research tree heights in montane forest blocks of Kenya. It uses a completely randomised block design to asses if differences exist in forest heights: 1) among montane fore...This study was designed to use LiDAR data to research tree heights in montane forest blocks of Kenya. It uses a completely randomised block design to asses if differences exist in forest heights: 1) among montane forest blocks, 2) among Agro ecological zones (AEZ) within each forest block and 3) between similar AEZ in different forest blocks. Forest height data from the Geoscience Laser Altimeter System (GLAS) on the Ice Cloud and Land Elevation Satellite (ICE-SAT) for the period 2003-2009 was used for 2146 circular plots, of 0.2 - 0.25 ha in size. Results indicate that, tree height is largely influenced by Agro ecological conditions and the wetter zones have taller trees in the upper, middle and lower highlands. In the upper highland zones of limited human activity, tree heights did not vary among forest blocks. Variations in height among forest blocks and within forest blocks were exaggerated in regions of active human intervention.展开更多
Based on gridded meteorological data for the period 1981-2100 from the RegCM3 regional model, the changing trends of climatic resources in Northeast China are analyzed, and the distributions of maize va-rieties are ac...Based on gridded meteorological data for the period 1981-2100 from the RegCM3 regional model, the changing trends of climatic resources in Northeast China are analyzed, and the distributions of maize va-rieties are accordingly adjusted. In order to explore the eff ects of diff erent adaptation countermeasures on climatic productivity and meteorological suitability in the future, maize cultivars with resistance to high temperatures and/or drought are selected. The results show that, in the future, there is likely to be a sig-nifi cant increase in thermal resources, and potential atmospheric evaporation will increase correspondingly. Meanwhile, radiation is predicted to increase signifi cantly during 2041-2070 in the growing season. How-ever, changes in precipitation are unlikely to be suffi cient enough to off set the intensifi cation in atmospheric evaporation caused by the temperature increase. Water resources and high temperatures are found to be the two major factors constraining grain yield. The results also show that the warming climate will be favorable for maize production where thermal resources are already limited, such as in central and northern Heilongjiang Province and eastern Jilin Province; while in areas that are already relatively warm, such as Liaoning Province, climatic productivity will be reduced. The climatic productivity and the meteorological suitability of maize are found to improve when the planting of resistant varieties is modeled. The utilization of agricultural climatic resources through the adaptation countermeasures of maize varieties is to increase obviously with time. Specifi cally, maize with drought-resistant properties will have a marked infl uence on meteorological suitability during 2011-2070, with suitable areas expanding. During 2071-2100, those maize varieties with their upper limit of optimum temperature and maximum temperature increased by 2℃, or water requirement reduced to 94%, or upper limit of optimum temperature and maximum temperature in-creased by 1℃and water 展开更多
Cultivation of pollinator-dependent crops has expanded globally, increasing our reliance on insect pollination. This essential ecosystem service is provided by a wide range of managed and wild pollinators whose abunda...Cultivation of pollinator-dependent crops has expanded globally, increasing our reliance on insect pollination. This essential ecosystem service is provided by a wide range of managed and wild pollinators whose abundance and diversity are thought to be in decline, threatening sustainable food production. In Cameroon, several studies on pollinator-dependent crops carried out in different agro-ecological zones (AEZ) have been published in national and international journals, in order to present the importance and impact of flowering insects on fruit and seed yields of plant species. We proposed to produce a review article highlighting the different flowering insects and their importance for different plants according to AEZ, without however focusing on the quality of the journal (predator or non-predator) and how the different insects were identified (scientific names given in the publications). Thus, from 1997 to 2020, we collected 116 published papers from which only 26 were kept for this review. The results show that Hymenoptera, including the Apidae, followed by Megachilidae, are the most excellent pollinators of plant species in Cameroon, and they are present in different agro-ecological zones. The majority of publications focused on bees, particularly the honeybee Apis mellifera.展开更多
Azadirachta indica seed samples were collected from four different agro-ecological regions（AERs） viz.,AER-2,AER-4,AER-5A and AER-5B of Gujarat state,India during 2000 to 2002 with an aim to assess variability in aza...Azadirachta indica seed samples were collected from four different agro-ecological regions（AERs） viz.,AER-2,AER-4,AER-5A and AER-5B of Gujarat state,India during 2000 to 2002 with an aim to assess variability in azadirachtin,oil and fatty acids content of the seeds and assess correlation of these parameters with morphological characters.Azadirachtin,oil and fatty acids content indicated significant（p0.01） variations between years and AERs in Gujarat.The azadirachtin ranged from 142 to 9 527 μg·g-1 seed kernel with an average of 2 426 μg·g-1 for the state.AER-5B recorded highest azadirachtin and oil content.Fatty acid composition was found to be affected by environmental factors particularly varying degree of annual rainfall and temperature during fruit ripening period.Conclusively trees growing in AER-5B performed better in term of azadirachtin,oil and stearic acid content.Tree girth at breast height showed no significant relation with these biochemicals.展开更多
Cowpea is a very popular foodstuff among people in sub-Saharan Africa. In Burkina Faso, it is the main food legume, especially in rural areas. Its production is facing difficulties including post-harvest losses caused...Cowpea is a very popular foodstuff among people in sub-Saharan Africa. In Burkina Faso, it is the main food legume, especially in rural areas. Its production is facing difficulties including post-harvest losses caused by fungi. Therefore, the objective of this study was to isolate and identify fungal strains associated with cowpea seeds produced in Burkina Faso. Thus, a total of 108 seed samples were collected in the three agro-ecological zones of Burkina Faso. The sanitary analysis of the seeds was carried out using the direct contact method. The isolation and purification of the isolates were performed on Potato Dextrose Agar medium while their identification was done through macroscopic and microscopic phenotypical characterization using different culture media (Potato Dextrose Agar (PDA), Malt Extract Agar (MEA) and Czapeck Dox Agar (CZA)) and different identification keys. A total of 10 fungal species were isolated, with predominance of Aspergillus flavus, Aspegillus niger, Macrophomina phaseolina, Fusarium oxysporium and Rhizopus sp. whose infection rates were 70.8% to 100% of seed samples. In addition to being present in all three zones, the infection rates of Aspergillus flavus (56.55%), Aspergillus niger (20.35%) and Rhizopus (32.80%) were higher in the Sahelian zone. In the Sudano-Sahelian zone, Macrophomina (50.66%) and Fusarium (18.88%) presented the highest infection rates, while Penicillium sp. showed the highest infection rate (2.84%) in the Sudanian zone. This finding demonstrated the necessity to improve post-harvest and conservation techniques of cowpea to limit crop losses and preserve the sanitary quality of this important foodstuff.展开更多
【目的】定量中国不同农业生态区和不同产量水平条件下的玉米百千克籽粒地上部吸氮量(N_(100)),分析气候、土壤、品种和施肥因素对玉米N_(100)的影响,为确定合理施氮量提供科学依据。【方法】将中国分为东北、西北、华北平原、长江中下...【目的】定量中国不同农业生态区和不同产量水平条件下的玉米百千克籽粒地上部吸氮量(N_(100)),分析气候、土壤、品种和施肥因素对玉米N_(100)的影响,为确定合理施氮量提供科学依据。【方法】将中国分为东北、西北、华北平原、长江中下游平原、西南和东南6大农作区,搜集1980—2022年发表的349篇符合要求的文献,通过数据统计分析不同区域和不同产量水平条件下的玉米N_(100),并分析采用统一和区域化的N_(100)计算出的理论施氮量差异,采用皮尔逊相关系数(pearson correlation coefficient)、随机森林(random forest)模型和整合分析(Meta-analysis)方法分析气候、土壤和施肥因素对玉米N_(100)的影响,揭示导致中国玉米N_(100)空间差异的原因。【结果】优化处理条件下,中国春玉米N_(100)显著低于夏玉米,分别为2.21和2.46;不同农业生态区玉米N_(100)存在显著差异,分别为2.19(东北春玉米)、2.12(西北春玉米)、2.54(西北夏玉米)、2.45(华北夏玉米)、2.77(长江中下游春玉米)、2.38(长江中下游夏玉米)和2.39(西南玉米区)。依据本研究全国玉米平均N_(100)(2.34)计算的理论施氮量与采用区域化的N_(100)计算得到的理论施氮量相差-22—31 kg N·hm^(-2)。地上部吸氮量、产量、年均气温是影响玉米N_(100)的最重要因素;N_(100)随产量增加呈显著二次曲线降低的趋势(P<0.01),籽粒产量可以很好地预测N_(100);品种显著影响玉米N_(100),中国常见的玉米品种郑单958、先玉335和登海605的N_(100)分别为2.42、2.12和2.39,新品种玉米N_(100)显著低于老品种。施用氮肥显著增加了玉米N_(100),且在施氮量200—300 kg N·hm^(-2)时,施氮肥引起的N_(100)增加效应最大。单施缓控释肥、深施氮肥、减少氮肥基施比例以及增加施氮次数均显著增加了玉米N_(100)。【结论】在利用N_(100)进行合理施氮量计算时,需要考虑不同农业生态区N_(100)的显�展开更多
Acid Lime (Citrus aurantifolia Swingle) is one of the important commercial fruits cultivated from terai to high hill of Nepal. It is an important source of vitamin “C” (ascorbic acid) for human nutrition. Amount of ...Acid Lime (Citrus aurantifolia Swingle) is one of the important commercial fruits cultivated from terai to high hill of Nepal. It is an important source of vitamin “C” (ascorbic acid) for human nutrition. Amount of juice, TSS (Total soluble solids), TA (Titrable acid) and vitamin C are the determining factors of quality of acid lime fruits which may vary according to bearing sides of the trees. The main objective of this study is, to determine the variation of fruit quality at different sides of the tree. Total of 15 bearing trees were selected randomly (5 trees per site) from three different agro ecological domain representing terai (1200 m asl) and samples were collected from the selected trees. Randomly ten fruits (from east, west, centre, north and south sides) were collected from each tree and analyzed for amount of vitamin C, TSS, TA and juice. Highest ascorbic acid 79.6 mg and 69.9 mg was observed in south side fruits whereas lowest 62.8 mg and 55.1 mg was observed in centre fruits in the high and mid hills zone respectively, but in terai, highest ascorbic acid 58.7 mg was observed in north side and lowest 41.8 mg was observed in centre. Highest amount of juice 43.9% was observed in south side fruits and lowest 36.6% in centre fruits, but amount of TSS 8.2% and TA 7.2% was observed in south side fruits and lowest 7.3% TSS and 7.0% TA was observed in centre fruits in high hills. In terai highest TSS 8.3% and TA 7.4% was observed in north side fruits and lowest TSS 7.3% and TA 6.7% was observed in centre fruits. Variation of TSS, TA percent and ascorbic acids was observed according to the agro ecological zone.展开更多
To determine the genetic diversity and population structure of sweet potato accessions cultivated in China, and to establish the genetic relationships among their germplasm types, a representative collection of 240 ac...To determine the genetic diversity and population structure of sweet potato accessions cultivated in China, and to establish the genetic relationships among their germplasm types, a representative collection of 240 accessions was analyzed using inter-simple sequence repeat （ISSR） markers. The mean genetic similarity coefifcient, Nei’s gene diversity, and shared allele distance of tested sweet potato accessions were 0.7302, 0.3167 and 0.2698, respectively. The 240 accessions could be divided into six subgroups and ifve subpopulations based on neighbor-joining （NJ） clustering and STRUCTURE results, and obvious genetic relationships among the tested sweet potato accessions were identiifed. The marker-based NJ clustering and population structure showed no distinct assignment pattern corresponding to lfesh color or geographical ecotype of the tested sweet potato germplasm. Analysis of molecular variance （AMOVA） revealed small but signiifcant difference between white and orange-lfeshed sweet potato accessions. Small but signiifcant difference were also observed among sweet potato accessions from the Southern summer-autumn sweet potato region, the Yellow River Basin spring and summer sweet potato region and the Yangtze River Basin summer sweet potato region. This study demonstrates that genetic diversity in the tested sweet potato germplasm collection in China is lower than that in some reported sweet potato germplasm collections from other regions. Pedigree investigations suggest that more diverse Chinese sweet potato varieties should be formed by broadening the selection scope of breeding parents and incorporating the introduced varieties into future breeding programs.展开更多
Maize grain is the second most vital food after wheat to humans and forms an important part of a human diet due to its nutrients. In Kenya, it is estimated that one out of every two acres of land put to crop productio...Maize grain is the second most vital food after wheat to humans and forms an important part of a human diet due to its nutrients. In Kenya, it is estimated that one out of every two acres of land put to crop production is under maize crop. Maize can also be fed whole to livestock (grazed or chopped and ensiled). Due to increased demand and the need for higher productivity, farmers have adopted modern farming methods which include use of fertilizers, pesticides, compost manure, and irrigation. Uses of these products elevate amounts of heavy metals in the soil. Such heavy metals such as lead (Pb) and cadmium when taken up by plants accumulate in the plants becoming toxic at high levels. It is essential to monitor these levels in grains and leaves to ensure they do not exceed the WHO permissible limits. This study aimed at monitoring the levels of heavy metals uptake in maize (Zea mays) grains and leaves is within permissible levels. Level of heavy metals in maize grains from different ecological zones in UG County had mean concentration of Zn 0.122, Cd 0.03, Cu 0.111, Co 0.04, and Pb 0.33 mg/kg. These results were below WHO standards except for Cadmium, Co, and Pb which were slightly higher than recommended standard. The study also found that maize leaves had mean concentration of Zn 0.115, Cd 0.04, Cu 0.117, Co. 0.041 and Pb 0.323 mg/kg. The results were below WHO standards except Co and Pb which had slightly higher levels than the recommended WHO standards. The analytical results from this study provided important baseline statistics on the concentration of selected heavy metals in maize grains and leaves besides being an important assessment of environmental pollution in rural areas where maize farming is predominant.展开更多
This study was aimed at assessing soil erosion, climate variation and how climate has affected both the agro climatic and agro-ological zones of Kerio Valley basin. The basin faces challenges especially soil loss, due...This study was aimed at assessing soil erosion, climate variation and how climate has affected both the agro climatic and agro-ological zones of Kerio Valley basin. The basin faces challenges especially soil loss, due to the massive degradation that takes place in Kerio valley. Due to the increase in rainfall recently experienced in the area, most of the top soil has been carried away leading to excessive degradation of the valley, causing soil loss in the basin and subsequent deposition of the sediments in Lake Kamnarok which is an oxbow lake posing it to the threat of extinction. All these aforementioned factors, i.e. soil erosion, climate variation and land degradation have contributed to reduction of water storage capacity of the Lake. The main objective of this study was to assess the effects of soil erosion, climate variation on the basin and climate effect on agro-climatic and agro-ecological zones of the basin. Agro-climatic zones show how climate variability shapes agricultural landscape of an area while agro-ological zones show how agriculture affects the ecology of the basin. This includes the reduction of the lake size that has led to the disruption of the ecology of Lake Kamnarok and its environs, the major implications being the lake size reduction as the lake is proved to be a home for reptiles especially crocodiles. All these factors were finally assessed to determine their effect on water reduction capacity of Lake Kamnarok. The results depicted that the major factors that have caused changes in the basin and the Lake include heavy rainfall that has resulted in soil erosion and subsequent land degradation. These factors have eventually affected the agroclimatic and agroecological zones of the basin. This study integrated the use of Geographic Information System (GIS) and Remote Sensing (RS) to assess the areas with massive degradation and to quantify the amount of soil loss using Revised Universal Soil Loss Equation (RUSLE) model. It was concluded that the main factor that caused the changes in t展开更多
文摘Species relative dominance by basal area was assessed along an agro ecological gradient in the Mau Forest Complex (MFC). Trees were recorded per species and diameter at breast height (D1.3) for size class D1.3 ≥ 10 cm in 60 quarter hectare plots distributed in 7 agro ecological zones (AEZ) namely LH1, LH2, LH3, LH4, UH0, UH1 and UH2. Basal area per species was used to calculate species relative dominance i.e. the proportion of basal area by a species to the total basal area of the AEZ. Species associations were analysed as the group of highly ranked species in each AEZ. Sorensons similarity index was used to calculate the proportion of similar species among AEZ. Analysis of variance compared basal area among AEZ and Tukey’s multiple comparison test used to identify specific AEZ with differences. Tabernaemontana stapfiana (Britten) was ranked first in LH1, UH1 and UH0 with relative dominance values of 22.66%, 22.89% and 30.73% respectively. It was however not recorded in any other AEZs. Dombeya goetzenii (K. Schum) occurred in 6 of the 7 AEZs but had moderate dominance values in each of the 6 AEZs. The sum of dominance values per species in all AEZs indicated no species mono-dominance and different species dominated at different AEZs. Co-dominance resulted in species associations like Tabernaemontana-Allophylus-Eke-bergia-Albizia in LH1, Juniperus-Dombeya-Casearia-Prunus in LH2, Acokanthera-Cussonia-Olea-Teclea in LH4 and Tabernaemontana-Syzygium-Podocarpus-Neoboutonia in UH1. Species richness was highest in UH1 and had the highest similarity indices with those of other AEZs. The UH1 had a species similarity of 67% with LH1, 63% with LH2 and 56% with LH4. However, species in the very humid zone UH0 differed with those of the drier lower highland zones (UH0 vs LH3 and vs LH4 = 31% and 37% respectively). Basal area differed significantly among AEZ ( = 3.76) showing that they differ in stocking levels. Tukeys test showed that high potential zones of LH1, LH2, UH0, UH1 did not differ and similarly the lower potent
文摘This study was designed to use LiDAR data to research tree heights in montane forest blocks of Kenya. It uses a completely randomised block design to asses if differences exist in forest heights: 1) among montane forest blocks, 2) among Agro ecological zones (AEZ) within each forest block and 3) between similar AEZ in different forest blocks. Forest height data from the Geoscience Laser Altimeter System (GLAS) on the Ice Cloud and Land Elevation Satellite (ICE-SAT) for the period 2003-2009 was used for 2146 circular plots, of 0.2 - 0.25 ha in size. Results indicate that, tree height is largely influenced by Agro ecological conditions and the wetter zones have taller trees in the upper, middle and lower highlands. In the upper highland zones of limited human activity, tree heights did not vary among forest blocks. Variations in height among forest blocks and within forest blocks were exaggerated in regions of active human intervention.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund(GYHY201106020)National Natural Science Foundation of China(31371530)
文摘Based on gridded meteorological data for the period 1981-2100 from the RegCM3 regional model, the changing trends of climatic resources in Northeast China are analyzed, and the distributions of maize va-rieties are accordingly adjusted. In order to explore the eff ects of diff erent adaptation countermeasures on climatic productivity and meteorological suitability in the future, maize cultivars with resistance to high temperatures and/or drought are selected. The results show that, in the future, there is likely to be a sig-nifi cant increase in thermal resources, and potential atmospheric evaporation will increase correspondingly. Meanwhile, radiation is predicted to increase signifi cantly during 2041-2070 in the growing season. How-ever, changes in precipitation are unlikely to be suffi cient enough to off set the intensifi cation in atmospheric evaporation caused by the temperature increase. Water resources and high temperatures are found to be the two major factors constraining grain yield. The results also show that the warming climate will be favorable for maize production where thermal resources are already limited, such as in central and northern Heilongjiang Province and eastern Jilin Province; while in areas that are already relatively warm, such as Liaoning Province, climatic productivity will be reduced. The climatic productivity and the meteorological suitability of maize are found to improve when the planting of resistant varieties is modeled. The utilization of agricultural climatic resources through the adaptation countermeasures of maize varieties is to increase obviously with time. Specifi cally, maize with drought-resistant properties will have a marked infl uence on meteorological suitability during 2011-2070, with suitable areas expanding. During 2071-2100, those maize varieties with their upper limit of optimum temperature and maximum temperature increased by 2℃, or water requirement reduced to 94%, or upper limit of optimum temperature and maximum temperature in-creased by 1℃and water
文摘Cultivation of pollinator-dependent crops has expanded globally, increasing our reliance on insect pollination. This essential ecosystem service is provided by a wide range of managed and wild pollinators whose abundance and diversity are thought to be in decline, threatening sustainable food production. In Cameroon, several studies on pollinator-dependent crops carried out in different agro-ecological zones (AEZ) have been published in national and international journals, in order to present the importance and impact of flowering insects on fruit and seed yields of plant species. We proposed to produce a review article highlighting the different flowering insects and their importance for different plants according to AEZ, without however focusing on the quality of the journal (predator or non-predator) and how the different insects were identified (scientific names given in the publications). Thus, from 1997 to 2020, we collected 116 published papers from which only 26 were kept for this review. The results show that Hymenoptera, including the Apidae, followed by Megachilidae, are the most excellent pollinators of plant species in Cameroon, and they are present in different agro-ecological zones. The majority of publications focused on bees, particularly the honeybee Apis mellifera.
基金supported by the NOVOD Board, Ministry of Agriculture, Government of India
文摘Azadirachta indica seed samples were collected from four different agro-ecological regions（AERs） viz.,AER-2,AER-4,AER-5A and AER-5B of Gujarat state,India during 2000 to 2002 with an aim to assess variability in azadirachtin,oil and fatty acids content of the seeds and assess correlation of these parameters with morphological characters.Azadirachtin,oil and fatty acids content indicated significant（p0.01） variations between years and AERs in Gujarat.The azadirachtin ranged from 142 to 9 527 μg·g-1 seed kernel with an average of 2 426 μg·g-1 for the state.AER-5B recorded highest azadirachtin and oil content.Fatty acid composition was found to be affected by environmental factors particularly varying degree of annual rainfall and temperature during fruit ripening period.Conclusively trees growing in AER-5B performed better in term of azadirachtin,oil and stearic acid content.Tree girth at breast height showed no significant relation with these biochemicals.
文摘Cowpea is a very popular foodstuff among people in sub-Saharan Africa. In Burkina Faso, it is the main food legume, especially in rural areas. Its production is facing difficulties including post-harvest losses caused by fungi. Therefore, the objective of this study was to isolate and identify fungal strains associated with cowpea seeds produced in Burkina Faso. Thus, a total of 108 seed samples were collected in the three agro-ecological zones of Burkina Faso. The sanitary analysis of the seeds was carried out using the direct contact method. The isolation and purification of the isolates were performed on Potato Dextrose Agar medium while their identification was done through macroscopic and microscopic phenotypical characterization using different culture media (Potato Dextrose Agar (PDA), Malt Extract Agar (MEA) and Czapeck Dox Agar (CZA)) and different identification keys. A total of 10 fungal species were isolated, with predominance of Aspergillus flavus, Aspegillus niger, Macrophomina phaseolina, Fusarium oxysporium and Rhizopus sp. whose infection rates were 70.8% to 100% of seed samples. In addition to being present in all three zones, the infection rates of Aspergillus flavus (56.55%), Aspergillus niger (20.35%) and Rhizopus (32.80%) were higher in the Sahelian zone. In the Sudano-Sahelian zone, Macrophomina (50.66%) and Fusarium (18.88%) presented the highest infection rates, while Penicillium sp. showed the highest infection rate (2.84%) in the Sudanian zone. This finding demonstrated the necessity to improve post-harvest and conservation techniques of cowpea to limit crop losses and preserve the sanitary quality of this important foodstuff.
文摘【目的】定量中国不同农业生态区和不同产量水平条件下的玉米百千克籽粒地上部吸氮量(N_(100)),分析气候、土壤、品种和施肥因素对玉米N_(100)的影响,为确定合理施氮量提供科学依据。【方法】将中国分为东北、西北、华北平原、长江中下游平原、西南和东南6大农作区,搜集1980—2022年发表的349篇符合要求的文献,通过数据统计分析不同区域和不同产量水平条件下的玉米N_(100),并分析采用统一和区域化的N_(100)计算出的理论施氮量差异,采用皮尔逊相关系数(pearson correlation coefficient)、随机森林(random forest)模型和整合分析(Meta-analysis)方法分析气候、土壤和施肥因素对玉米N_(100)的影响,揭示导致中国玉米N_(100)空间差异的原因。【结果】优化处理条件下,中国春玉米N_(100)显著低于夏玉米,分别为2.21和2.46;不同农业生态区玉米N_(100)存在显著差异,分别为2.19(东北春玉米)、2.12(西北春玉米)、2.54(西北夏玉米)、2.45(华北夏玉米)、2.77(长江中下游春玉米)、2.38(长江中下游夏玉米)和2.39(西南玉米区)。依据本研究全国玉米平均N_(100)(2.34)计算的理论施氮量与采用区域化的N_(100)计算得到的理论施氮量相差-22—31 kg N·hm^(-2)。地上部吸氮量、产量、年均气温是影响玉米N_(100)的最重要因素;N_(100)随产量增加呈显著二次曲线降低的趋势(P<0.01),籽粒产量可以很好地预测N_(100);品种显著影响玉米N_(100),中国常见的玉米品种郑单958、先玉335和登海605的N_(100)分别为2.42、2.12和2.39,新品种玉米N_(100)显著低于老品种。施用氮肥显著增加了玉米N_(100),且在施氮量200—300 kg N·hm^(-2)时,施氮肥引起的N_(100)增加效应最大。单施缓控释肥、深施氮肥、减少氮肥基施比例以及增加施氮次数均显著增加了玉米N_(100)。【结论】在利用N_(100)进行合理施氮量计算时,需要考虑不同农业生态区N_(100)的显�
文摘Acid Lime (Citrus aurantifolia Swingle) is one of the important commercial fruits cultivated from terai to high hill of Nepal. It is an important source of vitamin “C” (ascorbic acid) for human nutrition. Amount of juice, TSS (Total soluble solids), TA (Titrable acid) and vitamin C are the determining factors of quality of acid lime fruits which may vary according to bearing sides of the trees. The main objective of this study is, to determine the variation of fruit quality at different sides of the tree. Total of 15 bearing trees were selected randomly (5 trees per site) from three different agro ecological domain representing terai (1200 m asl) and samples were collected from the selected trees. Randomly ten fruits (from east, west, centre, north and south sides) were collected from each tree and analyzed for amount of vitamin C, TSS, TA and juice. Highest ascorbic acid 79.6 mg and 69.9 mg was observed in south side fruits whereas lowest 62.8 mg and 55.1 mg was observed in centre fruits in the high and mid hills zone respectively, but in terai, highest ascorbic acid 58.7 mg was observed in north side and lowest 41.8 mg was observed in centre. Highest amount of juice 43.9% was observed in south side fruits and lowest 36.6% in centre fruits, but amount of TSS 8.2% and TA 7.2% was observed in south side fruits and lowest 7.3% TSS and 7.0% TA was observed in centre fruits in high hills. In terai highest TSS 8.3% and TA 7.4% was observed in north side fruits and lowest TSS 7.3% and TA 6.7% was observed in centre fruits. Variation of TSS, TA percent and ascorbic acids was observed according to the agro ecological zone.
基金supported by the National Natural Science Foundation of China (31101192)the Animal and Plant Breeding Project of Chongqing,China (cstc2010AB1053)+2 种基金the Application Development Key Project of Chongqing,China (cstc2013yykfb80010)the Fundamental Research Funds for the Central Universities,China (XDJK2011C004)the "111" Project (B12006) of Ministry of Education,China
文摘To determine the genetic diversity and population structure of sweet potato accessions cultivated in China, and to establish the genetic relationships among their germplasm types, a representative collection of 240 accessions was analyzed using inter-simple sequence repeat （ISSR） markers. The mean genetic similarity coefifcient, Nei’s gene diversity, and shared allele distance of tested sweet potato accessions were 0.7302, 0.3167 and 0.2698, respectively. The 240 accessions could be divided into six subgroups and ifve subpopulations based on neighbor-joining （NJ） clustering and STRUCTURE results, and obvious genetic relationships among the tested sweet potato accessions were identiifed. The marker-based NJ clustering and population structure showed no distinct assignment pattern corresponding to lfesh color or geographical ecotype of the tested sweet potato germplasm. Analysis of molecular variance （AMOVA） revealed small but signiifcant difference between white and orange-lfeshed sweet potato accessions. Small but signiifcant difference were also observed among sweet potato accessions from the Southern summer-autumn sweet potato region, the Yellow River Basin spring and summer sweet potato region and the Yangtze River Basin summer sweet potato region. This study demonstrates that genetic diversity in the tested sweet potato germplasm collection in China is lower than that in some reported sweet potato germplasm collections from other regions. Pedigree investigations suggest that more diverse Chinese sweet potato varieties should be formed by broadening the selection scope of breeding parents and incorporating the introduced varieties into future breeding programs.
文摘Maize grain is the second most vital food after wheat to humans and forms an important part of a human diet due to its nutrients. In Kenya, it is estimated that one out of every two acres of land put to crop production is under maize crop. Maize can also be fed whole to livestock (grazed or chopped and ensiled). Due to increased demand and the need for higher productivity, farmers have adopted modern farming methods which include use of fertilizers, pesticides, compost manure, and irrigation. Uses of these products elevate amounts of heavy metals in the soil. Such heavy metals such as lead (Pb) and cadmium when taken up by plants accumulate in the plants becoming toxic at high levels. It is essential to monitor these levels in grains and leaves to ensure they do not exceed the WHO permissible limits. This study aimed at monitoring the levels of heavy metals uptake in maize (Zea mays) grains and leaves is within permissible levels. Level of heavy metals in maize grains from different ecological zones in UG County had mean concentration of Zn 0.122, Cd 0.03, Cu 0.111, Co 0.04, and Pb 0.33 mg/kg. These results were below WHO standards except for Cadmium, Co, and Pb which were slightly higher than recommended standard. The study also found that maize leaves had mean concentration of Zn 0.115, Cd 0.04, Cu 0.117, Co. 0.041 and Pb 0.323 mg/kg. The results were below WHO standards except Co and Pb which had slightly higher levels than the recommended WHO standards. The analytical results from this study provided important baseline statistics on the concentration of selected heavy metals in maize grains and leaves besides being an important assessment of environmental pollution in rural areas where maize farming is predominant.
文摘This study was aimed at assessing soil erosion, climate variation and how climate has affected both the agro climatic and agro-ological zones of Kerio Valley basin. The basin faces challenges especially soil loss, due to the massive degradation that takes place in Kerio valley. Due to the increase in rainfall recently experienced in the area, most of the top soil has been carried away leading to excessive degradation of the valley, causing soil loss in the basin and subsequent deposition of the sediments in Lake Kamnarok which is an oxbow lake posing it to the threat of extinction. All these aforementioned factors, i.e. soil erosion, climate variation and land degradation have contributed to reduction of water storage capacity of the Lake. The main objective of this study was to assess the effects of soil erosion, climate variation on the basin and climate effect on agro-climatic and agro-ecological zones of the basin. Agro-climatic zones show how climate variability shapes agricultural landscape of an area while agro-ological zones show how agriculture affects the ecology of the basin. This includes the reduction of the lake size that has led to the disruption of the ecology of Lake Kamnarok and its environs, the major implications being the lake size reduction as the lake is proved to be a home for reptiles especially crocodiles. All these factors were finally assessed to determine their effect on water reduction capacity of Lake Kamnarok. The results depicted that the major factors that have caused changes in the basin and the Lake include heavy rainfall that has resulted in soil erosion and subsequent land degradation. These factors have eventually affected the agroclimatic and agroecological zones of the basin. This study integrated the use of Geographic Information System (GIS) and Remote Sensing (RS) to assess the areas with massive degradation and to quantify the amount of soil loss using Revised Universal Soil Loss Equation (RUSLE) model. It was concluded that the main factor that caused the changes in t
