Pub Date : 2004-01-01DOI: 10.1080/00128325.2004.11663412
C. Njoroge, E. Kerbel
Ethylene Forming Enzyme (EFE) is the enzyme that catalyses the final step in the biosynthesis of ethylene (Kende, 1990; Yang etal., 1990; Yang and Hoffinan, 1984). The site of location of this enzyme in the plant cell is still unknown with certainty.' Mattoo and Lieberman (1977) suggested that it is localised in a cell wall-cell membrane complex. Bouzayen et al., 1990) suggested that there are two sites for EFE location in a plant cell. One of the sites is located on the plasmalemma and is very sensitive to plasmolysis of the cell, and the other site is in the tonoplast and its ethylene-forming ability is not affected by plasmolysis. These authors excluded the cell wall as a possible site for EFE location. Ververidis and John (1990) confirmed the findings of Bouzayens etal.; and also suggested that the actual EFE location depends on the stage of plant growth. Irrespective of the site of EFE location, it had been felt that it could only oxidise 1aminocyclopropane-carboxylic acid (ACC) to ethylene effectively if bound to the membrane, as its activity had not been recovered in vitro (John et al., 1985; Venis, 1984; Porter et al., 1986; Mayne and Kende, 1986). However, Ververidis and John (1991), fully recovered EFE activity in a cell free system from melon (Cucurnis melo) fruits. Other cell free systems have been reported to oxidise ACC to ethylene, but all the systems have a very high K,„ for ACC in the plant and this rules out the possibility of such systems being operative in the plant systems in-vivo because of their high Kin values for ACC. (McKeon and Yang, 1984; Stegink et al., 1986; Nielsen et al., 1984; Venis, 1984; Mayak etal., 1981).
乙烯形成酶(EFE)是催化乙烯生物合成最后一步的酶(Kende, 1990;杨等等。, 1990;Yang and Hoffinan, 1984)。这种酶在植物细胞中的位置仍然是未知的。”Mattoo和Lieberman(1977)认为它定位于细胞壁-细胞膜复合体。Bouzayen et al.， 1990)认为EFE在植物细胞中有两个位置。其中一个位点位于细胞质膜上，对细胞的质解非常敏感，另一个位点位于细胞质内，其乙烯生成能力不受质解的影响。这些作者排除了细胞壁作为EFE定位的可能位点。Ververidis和John(1990)证实了Bouzayens等人的发现;结果表明，EFE的实际位置取决于植物的生长阶段。无论EFE的位置如何，人们认为它只能在与膜结合时有效地将1氨基环丙烷-羧酸(ACC)氧化为乙烯，因为它的活性在体外没有恢复(John等人，1985;像,1984;Porter et al.， 1986;Mayne and Kende, 1986)。然而，Ververidis和John(1991)在甜瓜果实的无细胞系统中完全恢复了EFE活性。据报道，其他无细胞系统将ACC氧化为乙烯，但所有系统都有非常高的K，“对于植物中的ACC，这排除了这些系统在植物体内系统中运作的可能性，因为它们的ACC的Kin值很高。(McKeon and Yang, 1984;Stegink et al.， 1986;Nielsen et al.， 1984;像,1984;克等等。, 1981)。
{"title":"Recovery of Ethylene Forming Enzyme from Green Pea Pods","authors":"C. Njoroge, E. Kerbel","doi":"10.1080/00128325.2004.11663412","DOIUrl":"https://doi.org/10.1080/00128325.2004.11663412","url":null,"abstract":"Ethylene Forming Enzyme (EFE) is the enzyme that catalyses the final step in the biosynthesis of ethylene (Kende, 1990; Yang etal., 1990; Yang and Hoffinan, 1984). The site of location of this enzyme in the plant cell is still unknown with certainty.' Mattoo and Lieberman (1977) suggested that it is localised in a cell wall-cell membrane complex. Bouzayen et al., 1990) suggested that there are two sites for EFE location in a plant cell. One of the sites is located on the plasmalemma and is very sensitive to plasmolysis of the cell, and the other site is in the tonoplast and its ethylene-forming ability is not affected by plasmolysis. These authors excluded the cell wall as a possible site for EFE location. Ververidis and John (1990) confirmed the findings of Bouzayens etal.; and also suggested that the actual EFE location depends on the stage of plant growth. Irrespective of the site of EFE location, it had been felt that it could only oxidise 1aminocyclopropane-carboxylic acid (ACC) to ethylene effectively if bound to the membrane, as its activity had not been recovered in vitro (John et al., 1985; Venis, 1984; Porter et al., 1986; Mayne and Kende, 1986). However, Ververidis and John (1991), fully recovered EFE activity in a cell free system from melon (Cucurnis melo) fruits. Other cell free systems have been reported to oxidise ACC to ethylene, but all the systems have a very high K,„ for ACC in the plant and this rules out the possibility of such systems being operative in the plant systems in-vivo because of their high Kin values for ACC. (McKeon and Yang, 1984; Stegink et al., 1986; Nielsen et al., 1984; Venis, 1984; Mayak etal., 1981).","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"5 1","pages":"1 - 6"},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87895507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v68i4.1797
B. A. Were, A. Onkware, S. Gudu
Sweetpotato (Ipomoea batatas [L.] Lam.) is an important food crop in the tropics. In Kenya, it is mainly grown by small-scale fanners for food security during months of food scarcity. Nyanza Province produces 53% of the total national output (Irungu and Kidane-Mariam, 1992). Sweetpotato cultivation is common in the Nyatike and Mbita Divisions in the dry lowlands of Lake Victoria basin. The yield is low because of prevalent drought, weevil infestation and viral attack (Gudu and Were, 1996). The farmers in the two Divisions still grow land races in soils that are low in fertility, which further reduces the crop yield. Introduction of the high yielding, drought-tolerant cultivars that have been selected by the Kenya Agricultural Research Institute (KARI) and the International Potato Center (CIP) could improve yield. Apart from high yield potential, some of the cultivars are resistant to viral and pest attack (Mutuura et al., 1992).
甘薯(iomoea batatas);是热带地区重要的粮食作物。在肯尼亚，在粮食短缺的几个月里，它主要由小农种植，用于粮食安全。尼扬扎省的产出占全国总产出的53% (Irungu和Kidane-Mariam, 1992)。甘薯种植在维多利亚湖盆地干燥低地的尼亚蒂克和姆比塔地区很常见。由于普遍干旱、象鼻虫侵扰和病毒侵袭，产量很低(Gudu和Were, 1996年)。这两个地区的农民仍然在低肥力的土壤上种植土地品种，这进一步降低了作物产量。引进由肯尼亚农业研究所(KARI)和国际马铃薯中心(CIP)选择的高产耐旱品种可以提高产量。除了高产潜力外，一些品种对病毒和害虫具有抗性(Mutuura et al.， 1992)。
{"title":"Yield and Storage Quality of Improved Sweetpotato (Ipomoea Batatas [L.] Lam.) Cultivars in the Lake Victoria Basin, Kenya","authors":"B. A. Were, A. Onkware, S. Gudu","doi":"10.4314/eaafj.v68i4.1797","DOIUrl":"https://doi.org/10.4314/eaafj.v68i4.1797","url":null,"abstract":"Sweetpotato (Ipomoea batatas [L.] Lam.) is an important food crop in the tropics. In Kenya, it is mainly grown by small-scale fanners for food security during months of food scarcity. Nyanza Province produces 53% of the total national output (Irungu and Kidane-Mariam, 1992). Sweetpotato cultivation is common in the Nyatike and Mbita Divisions in the dry lowlands of Lake Victoria basin. The yield is low because of prevalent drought, weevil infestation and viral attack (Gudu and Were, 1996). The farmers in the two Divisions still grow land races in soils that are low in fertility, which further reduces the crop yield. Introduction of the high yielding, drought-tolerant cultivars that have been selected by the Kenya Agricultural Research Institute (KARI) and the International Potato Center (CIP) could improve yield. Apart from high yield potential, some of the cultivars are resistant to viral and pest attack (Mutuura et al., 1992).","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"11 4","pages":"197 - 204"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91462814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v69i1.1804
P. Macharia
ABSTRACT Sustainable natural resources management, particularly soil management, requires integration of farmers', researchers' and other stakeholders' knowledge for enhanced rural development. A field study was conducted by an interdisciplinary team of scientists in Kasikeu Sub-Location of Makueni District, Kenya, to assist in integrating farmers' and scientists' knowledge on soils in a participatory soil mapping. Gender-sensitive farmer group meetings, on-site discussions, transect walks, soil profile descriptions, and laboratory soil analyses were used for the study. The results of the study showed that farmers in Kasikeu mainly used soil surface characteristics such as colour, texture and coarseness to classify soils. Scientists on the other hand used the FAO/UNESCO Legend for the Soil Map of the World which lays emphasis on the characteristics of the subsoil. Further, at farm level, fanners know in detail the soil types, uses, and management of their soil after living and working on the soils for a long time. Scientists, on the other hand, acquire the knowledge on the soils in a relatively short time through soil survey, testing and classification. The analytical and other scientific data complements the farmers', knowledge on aspects that they cannot interpret. The women farmers have more detailed information on soils than men farmers, since the women are more involved in farming activities. Finally, the study showed that integration of indigenous knowledge provided by farmers and the scientific knowhow and facilities provided by the scientists underscored the fact that farmers and scientists need each other. In this way, scientists will be in a better position to identify the most appropriate agricultural interventions for improving soil productivity.
{"title":"Integrating Farmers' and Scientists' Knowledge in Participatory Soil Mapping and Management: A Case Study from Semi-Arid Eastern Kenya","authors":"P. Macharia","doi":"10.4314/eaafj.v69i1.1804","DOIUrl":"https://doi.org/10.4314/eaafj.v69i1.1804","url":null,"abstract":"ABSTRACT Sustainable natural resources management, particularly soil management, requires integration of farmers', researchers' and other stakeholders' knowledge for enhanced rural development. A field study was conducted by an interdisciplinary team of scientists in Kasikeu Sub-Location of Makueni District, Kenya, to assist in integrating farmers' and scientists' knowledge on soils in a participatory soil mapping. Gender-sensitive farmer group meetings, on-site discussions, transect walks, soil profile descriptions, and laboratory soil analyses were used for the study. The results of the study showed that farmers in Kasikeu mainly used soil surface characteristics such as colour, texture and coarseness to classify soils. Scientists on the other hand used the FAO/UNESCO Legend for the Soil Map of the World which lays emphasis on the characteristics of the subsoil. Further, at farm level, fanners know in detail the soil types, uses, and management of their soil after living and working on the soils for a long time. Scientists, on the other hand, acquire the knowledge on the soils in a relatively short time through soil survey, testing and classification. The analytical and other scientific data complements the farmers', knowledge on aspects that they cannot interpret. The women farmers have more detailed information on soils than men farmers, since the women are more involved in farming activities. Finally, the study showed that integration of indigenous knowledge provided by farmers and the scientific knowhow and facilities provided by the scientists underscored the fact that farmers and scientists need each other. In this way, scientists will be in a better position to identify the most appropriate agricultural interventions for improving soil productivity.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"25 1","pages":"39 - 47"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89180767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v68i4.1798
C. Asadu, C.S. Bosah
The soils of Nsukka in eastern Nigeria have generally been derived from the residua (disintegrated rock materials) of either Falsebedded Sandstone or Upper Coal Measure Formations (Asadu, 1990). These geological formations usually give rise to sandy and clayey soils (Akamigbo and Asadu, 1983). The Upper Coal Measures occupy the upper slopes and tops of residual hills in the area but residua from them are transported by colluviation or erosion processes to the lower plains to form soils of similar characteristics with those of the upper slopes. This study was carried out on soils derived from such colluvial materials. The selected sites were contiguous, hence land use was the only differentiating factor among the locations.
{"title":"A Comparative Study of the Soils of the Upper Coalmeasure Residua Under Cropped-Grass-Forest Landcontinuum in Eastern Nigeria","authors":"C. Asadu, C.S. Bosah","doi":"10.4314/eaafj.v68i4.1798","DOIUrl":"https://doi.org/10.4314/eaafj.v68i4.1798","url":null,"abstract":"The soils of Nsukka in eastern Nigeria have generally been derived from the residua (disintegrated rock materials) of either Falsebedded Sandstone or Upper Coal Measure Formations (Asadu, 1990). These geological formations usually give rise to sandy and clayey soils (Akamigbo and Asadu, 1983). The Upper Coal Measures occupy the upper slopes and tops of residual hills in the area but residua from them are transported by colluviation or erosion processes to the lower plains to form soils of similar characteristics with those of the upper slopes. This study was carried out on soils derived from such colluvial materials. The selected sites were contiguous, hence land use was the only differentiating factor among the locations.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"5 1","pages":"205 - 212"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75863230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v69i2.1816
F. Muyekho, J. Mureithi, J. Ngeny
ABSTRACT Forage legumes are important in the smallholder farming system since they increase the quality of livestock feeds and soil fertility through quality manure. The legumes can also concurrently enhance soil fertility through nitrogen fixation for companion grasses and subsequent cereal crops. Farmers in Kenya are aware of the importance of forage legumes but stunted/slow growth during the establishment year and non availability of low cost seed has limited adoption of this technology. Two experiments were carried out on nitrogen and phosphorus-deficient soils at the National Agricultural Research Centre Kitale. In experiment 1 the effects of nitrogen applied at the rates of 0, 10, 20, 40, 60, 80 and 100 kg N/ha were evaluated for nodulation and dry matter accumulation of Desmodium uncinatum. Experiment 2 evaluated the effects of 0, 23, 46, 69, 92, 115 kg P2O5/ha in the form of single superphosphate fertiliser and 10, 20, 30 and 40 t/ha of farm yard manure on nodulation, herbage dry matter and seed yields of Desmodium uncinatum. A randomized complete block design with 3 replicates was used in each experiment. Nitrogen fertilisers did not increase nodulation and dry matter yields significantly. Increasing nitrogen fertiliser rates beyond 20 kg N/ha resulted in a significant (P<0.01) decline in the total and number of effective nodules produced per plant. Herbage dry matter yields also significantly (P<0.01) declined with application of more than 40 kg N/ha. Application of 23 and 46 kg P2O5/ha significantly (P<0.05) increased nodulation (total and effective number of nodules) and herbage dry matter yields. However, for 2 years there was no advantage in applying rates exceeding 46 P2O5/ha. Farm yard manure also significantly (P<0.5) increased nodulation but there were no significant differences between application of 10 t/ha and higher rates of 20, 30 or 40 t/ha. Herbage dry matter yields were increased by application of farm yard manure though the results were not significant at P>0.05. Seed yields were not significantly increased by phosphate or farmyard manure application.
草料豆科植物在小农农业系统中非常重要，因为它们通过优质肥料提高了牲畜饲料质量和土壤肥力。豆科植物还可以同时通过对伴生草和随后的谷类作物的固氮来提高土壤肥力。肯尼亚的农民意识到草料豆科作物的重要性，但在种植年份生长迟缓，且无法获得低成本种子，限制了该技术的采用。在基塔莱国家农业研究中心对缺氮和缺磷土壤进行了两项试验。试验1研究了0、10、20、40、60、80和100 kg N/ha施氮量对刺青结瘤和干物质积累的影响。试验2评价了0、23、46、69、92、115 kg P2O5/ha单一过磷肥和10、20、30、40 t/ha农家肥对刺青结瘤、牧草干物质和种子产量的影响。试验采用完全随机区组设计，每个试验设3个重复。氮肥对结瘤和干物质产量的提高不显著。施氮量超过20 kg N/ha后，显著提高(P0.05)。施用磷肥和农家肥对种子产量无显著影响。
{"title":"Effects of Rates of Inorganic and Organic Fertilisers on Desmodium uncinatum Nodulation, Dry Matter and Seed Yields on Phosphorus and Nitrogen Deficient Soils","authors":"F. Muyekho, J. Mureithi, J. Ngeny","doi":"10.4314/eaafj.v69i2.1816","DOIUrl":"https://doi.org/10.4314/eaafj.v69i2.1816","url":null,"abstract":"ABSTRACT Forage legumes are important in the smallholder farming system since they increase the quality of livestock feeds and soil fertility through quality manure. The legumes can also concurrently enhance soil fertility through nitrogen fixation for companion grasses and subsequent cereal crops. Farmers in Kenya are aware of the importance of forage legumes but stunted/slow growth during the establishment year and non availability of low cost seed has limited adoption of this technology. Two experiments were carried out on nitrogen and phosphorus-deficient soils at the National Agricultural Research Centre Kitale. In experiment 1 the effects of nitrogen applied at the rates of 0, 10, 20, 40, 60, 80 and 100 kg N/ha were evaluated for nodulation and dry matter accumulation of Desmodium uncinatum. Experiment 2 evaluated the effects of 0, 23, 46, 69, 92, 115 kg P2O5/ha in the form of single superphosphate fertiliser and 10, 20, 30 and 40 t/ha of farm yard manure on nodulation, herbage dry matter and seed yields of Desmodium uncinatum. A randomized complete block design with 3 replicates was used in each experiment. Nitrogen fertilisers did not increase nodulation and dry matter yields significantly. Increasing nitrogen fertiliser rates beyond 20 kg N/ha resulted in a significant (P<0.01) decline in the total and number of effective nodules produced per plant. Herbage dry matter yields also significantly (P<0.01) declined with application of more than 40 kg N/ha. Application of 23 and 46 kg P2O5/ha significantly (P<0.05) increased nodulation (total and effective number of nodules) and herbage dry matter yields. However, for 2 years there was no advantage in applying rates exceeding 46 P2O5/ha. Farm yard manure also significantly (P<0.5) increased nodulation but there were no significant differences between application of 10 t/ha and higher rates of 20, 30 or 40 t/ha. Herbage dry matter yields were increased by application of farm yard manure though the results were not significant at P>0.05. Seed yields were not significantly increased by phosphate or farmyard manure application.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"2 1","pages":"149 - 156"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90562497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v69i2.1817
G. Okwach, M. Siambi, C. Simiyu
ABSTRACT The APSIM model was used to evaluate a range of maize densities on a sandy-clay loam at Kenya Agricultural Research Institute (KARJ)-Katumani Research Centre in Machakos and 2 contrasting farmers' fields situated on sandy and clay soil types. Each simulation was initialised with actual soil parameters measured at the time of commencing the run. Simulations on the Katumani soil were done under 5 contrasting Short Rainy i SR.) seasons of different rainfall regimes, namely SR1996 (185 mm), SR1995 (270 mm), SR1991 (328 mm), SR1992 (720 mm), and the El Nino season of SR1997 (958 mm). Maize densities used were 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 plants/m2. The model showed that maize grain yield declined as density increased under the poor 1996 season. Optimum crop density increased with seasonal rainfall, to reach 5.0 plants/m2 in the 1992 and 1997 heavy rainfall seasons. On the farmers' fields, APSIM showed that the clay soil out-yielded the sandy soil in high rainfall, while the reverse was true on poorer seasons. Simulations were done to determine the effects of varying nitrogen at constant crop density of 5.3 plants/m2. Nitrogen rates used were 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 120 kg/ha. The response of maize to N fertiliser varied with seasonal rainfall. Grain yields were depressed when N was added to maize during the poorer SR1996 and SR1995 seasons. With higher seasonal rainfall, APSIM predicted a sharp increase in grain yield at low rates of N. Simulations of the effects of N on maize yield on the 3 farmers' fields (clay and sandy soils) were done for SR1997 (1310 mm) and SR1998 (122 mm) seasons, using N rates of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 kg ha. The model predicted crop failure for the SR1998 season on the clay soil throughout all levels of N rates. In the wet SR1997, grain yield was low at 0 to 30 kg N/ha, and then increased sharply at levels greater than 30 kg N/ha. The response to N was, therefore, highest in the clay soil under wet conditions. Grain yield responded well in the sandy soil during SR1997, though the rate of response was lower than in the clay soil. However, the sandy soil proved superior to clay in the poor season (SR1998). A gradual response to N was predicted in the sanity soil, up to 30 kg N/ha. Sowing date was more important for sandy than clay soil type. Delayed sowing on the clay soil type did not adversely affect yield, whereas a week's delay on the sandy soils led to a yield decline even in a favourable season.
应用APSIM模型对位于马查科斯的肯尼亚农业研究所(KARJ)-Katumani研究中心的砂质-粘土壤土上的玉米密度范围进行了评估，并对位于砂质和粘土类型上的2个农民的农田进行了对比。每次模拟都是用开始运行时测量的实际土壤参数初始化的。在SR1996 (185 mm)、SR1995 (270 mm)、SR1991 (328 mm)、SR1992 (720 mm)和SR1997 (958 mm) 5个不同降雨条件下，对Katumani土壤进行了模拟。玉米密度分别为1、2、3、4、5、6、7、8、9和10株/m2。模型表明，在1996年较差的季节，玉米籽粒产量随着密度的增加而下降。最佳作物密度随季节降水增加而增加，1992年和1997年强降雨季节达到5.0株/m2。在农民的田间，APSIM显示，在高降雨季节，粘土的产量高于沙土，而在较差的季节，情况正好相反。模拟了在5.3株/m2等作物密度下，不同氮肥处理的效果。施氮量分别为0、10、20、30、40、50、60、70、80、90、100、110、120、130、140、150、160、170、180、190和120 kg/ha。玉米对氮肥的响应随季节降雨而变化。在1996年和1995年玉米产量较差的季节，施氮抑制了玉米产量。在季节性降雨较多的情况下，APSIM预测在低施氮量条件下粮食产量会急剧增加。在SR1997 (1310 mm)和SR1998 (122 mm)季节，分别采用0、10、20、30、40、50、60、70、80、90和100 kg ha施氮量，模拟了氮素对3个农民田(粘土和沙土)玉米产量的影响。该模型预测了SR1998季节不同施氮水平黏土的作物歉收情况。在1997年旱作中，0 ~ 30 kg N/ha时产量较低，大于30 kg N/ha时产量急剧增加。因此，湿润条件下粘土对氮的响应最大。在SR1997期间，沙质土壤的粮食产量响应良好，但响应速率低于粘土土壤。然而，在贫瘠的季节，沙质土壤被证明优于粘土(SR1998)。正常土壤对N的响应逐渐增大，达到30 kg N/ha。播期对砂质土壤比粘土土壤更重要。在粘土类型上延迟播种不会对产量产生不利影响，而在砂质土壤上延迟一周即使在有利季节也会导致产量下降。
{"title":"Assessing the Interaction in Maize Cropping Density, Nitrogen and Soil Moisture with a Systems Simulator in Semi-Arid Machakos District, Kenya","authors":"G. Okwach, M. Siambi, C. Simiyu","doi":"10.4314/eaafj.v69i2.1817","DOIUrl":"https://doi.org/10.4314/eaafj.v69i2.1817","url":null,"abstract":"ABSTRACT The APSIM model was used to evaluate a range of maize densities on a sandy-clay loam at Kenya Agricultural Research Institute (KARJ)-Katumani Research Centre in Machakos and 2 contrasting farmers' fields situated on sandy and clay soil types. Each simulation was initialised with actual soil parameters measured at the time of commencing the run. Simulations on the Katumani soil were done under 5 contrasting Short Rainy i SR.) seasons of different rainfall regimes, namely SR1996 (185 mm), SR1995 (270 mm), SR1991 (328 mm), SR1992 (720 mm), and the El Nino season of SR1997 (958 mm). Maize densities used were 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 plants/m2. The model showed that maize grain yield declined as density increased under the poor 1996 season. Optimum crop density increased with seasonal rainfall, to reach 5.0 plants/m2 in the 1992 and 1997 heavy rainfall seasons. On the farmers' fields, APSIM showed that the clay soil out-yielded the sandy soil in high rainfall, while the reverse was true on poorer seasons. Simulations were done to determine the effects of varying nitrogen at constant crop density of 5.3 plants/m2. Nitrogen rates used were 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 120 kg/ha. The response of maize to N fertiliser varied with seasonal rainfall. Grain yields were depressed when N was added to maize during the poorer SR1996 and SR1995 seasons. With higher seasonal rainfall, APSIM predicted a sharp increase in grain yield at low rates of N. Simulations of the effects of N on maize yield on the 3 farmers' fields (clay and sandy soils) were done for SR1997 (1310 mm) and SR1998 (122 mm) seasons, using N rates of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 kg ha. The model predicted crop failure for the SR1998 season on the clay soil throughout all levels of N rates. In the wet SR1997, grain yield was low at 0 to 30 kg N/ha, and then increased sharply at levels greater than 30 kg N/ha. The response to N was, therefore, highest in the clay soil under wet conditions. Grain yield responded well in the sandy soil during SR1997, though the rate of response was lower than in the clay soil. However, the sandy soil proved superior to clay in the poor season (SR1998). A gradual response to N was predicted in the sanity soil, up to 30 kg N/ha. Sowing date was more important for sandy than clay soil type. Delayed sowing on the clay soil type did not adversely affect yield, whereas a week's delay on the sandy soils led to a yield decline even in a favourable season.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"87 1","pages":"157 - 171"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73489570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v69i1.1806
F. Kihanda
ABSTRACT Nitrogen is a major limiting nutrient in the maize-growing areas of central Kenya highlands. Due to the high cost of inorganic fertilisers, the majority of the farmers use farmyard manure (FYM) to improve crop productivity. However, FYM produced in the area is often of low quality particularly in terms of N concentration. Studies previously carried out in the region showed that composting FYM with different proportions of Tithonia diversifolia (tithonia) or Lantana camara (lantana) improved the N content of the manure considerably. This study was conducted to test whether composted manure would improve growth and yield of maize. A field trial consisting of seven treatments: FYM composted with tithonia (1:1 and 3:1 ratios), or lantana (1:1 and 3:1 ratios), FYM composted alone, inorganic N fertiliser and an absolute control was laid out in low N site. Maize (Zea mays cv. Hybrid 513) was the test crop. The treatments were arranged in a RCBD replicated 3 times. The various compost types and the inorganic fertiliser were applied at an equivalent rate of 100 kg N/ha. Above ground maize biomass was taken at 2, 6, 10, 14 and 18 weeks after crop emergence, dried to a constant weight and the N content determined. The plant N uptake for each period was calculated as a product of dry matter and N content in the maize tissue. Grain yield was adjusted to 13% moisture content. It was observed that dry matter yield, N uptake and final grain yield of maize were significantly higher in FYM composted with tithonia or lantana than the control or FYM composted alone treatments. Amongst the composts, the highest dry matter accumulation and N uptake was observed in FYM composted with tithonia at 1:1 ratio. Inorganic fertiliser treatments gave the highest dry matter and N uptake. Based on the growth and N uptake in the fertiliser treatment it was concluded that the N release in all the compost was lower than the crop demand.
氮是肯尼亚中部高原玉米种植区的主要限制性养分。由于无机肥料成本高，大多数农民使用农家肥(FYM)来提高作物生产力。然而，该地区生产的FYM通常质量较低，特别是在氮浓度方面。以前在该地区进行的研究表明，在FYM中添加不同比例的Tithonia difolia (Tithonia)或Lantana camara (Lantana camara)可显著提高肥料的N含量。本试验旨在研究堆肥对玉米生长和产量的促进作用。在低氮试验区，采用7个处理:FYM与铁磷(1:1和3:1的比例)堆肥，或lantana(1:1和3:1的比例)，FYM单独堆肥，无机氮肥和绝对对照。玉米(Zea mays cv.)杂交种513是试验作物。这些处理被安排在一个重复3次的RCBD中。不同类型的堆肥和无机肥料按100 kg N/ha的等量施用。分别于作物出苗后2、6、10、14和18周采集玉米地上生物量，干燥至定重，测定氮含量。以玉米组织中干物质和氮含量的乘积计算各生育期植株的氮吸收量。籽粒产量调整为含水率13%。结果表明，在玉米干物质产量、氮素吸收量和终粒产量方面，掺加铁磷或蓝苔处理的FYM显著高于对照或单独堆肥处理。干物质积累量和氮素吸收量均以1:1比例加硫的FYM堆肥最高。无机肥处理对干物质和氮的吸收最高。综合各施肥处理的生长和氮素吸收情况，认为所有堆肥的氮素释放量均低于作物需要量。
{"title":"Effect of Manures Composted with High Quality Organic Residues on Dry Matter Accumulation, Nitrogen Uptake and Maize Grain Yield","authors":"F. Kihanda","doi":"10.4314/eaafj.v69i1.1806","DOIUrl":"https://doi.org/10.4314/eaafj.v69i1.1806","url":null,"abstract":"ABSTRACT Nitrogen is a major limiting nutrient in the maize-growing areas of central Kenya highlands. Due to the high cost of inorganic fertilisers, the majority of the farmers use farmyard manure (FYM) to improve crop productivity. However, FYM produced in the area is often of low quality particularly in terms of N concentration. Studies previously carried out in the region showed that composting FYM with different proportions of Tithonia diversifolia (tithonia) or Lantana camara (lantana) improved the N content of the manure considerably. This study was conducted to test whether composted manure would improve growth and yield of maize. A field trial consisting of seven treatments: FYM composted with tithonia (1:1 and 3:1 ratios), or lantana (1:1 and 3:1 ratios), FYM composted alone, inorganic N fertiliser and an absolute control was laid out in low N site. Maize (Zea mays cv. Hybrid 513) was the test crop. The treatments were arranged in a RCBD replicated 3 times. The various compost types and the inorganic fertiliser were applied at an equivalent rate of 100 kg N/ha. Above ground maize biomass was taken at 2, 6, 10, 14 and 18 weeks after crop emergence, dried to a constant weight and the N content determined. The plant N uptake for each period was calculated as a product of dry matter and N content in the maize tissue. Grain yield was adjusted to 13% moisture content. It was observed that dry matter yield, N uptake and final grain yield of maize were significantly higher in FYM composted with tithonia or lantana than the control or FYM composted alone treatments. Amongst the composts, the highest dry matter accumulation and N uptake was observed in FYM composted with tithonia at 1:1 ratio. Inorganic fertiliser treatments gave the highest dry matter and N uptake. Based on the growth and N uptake in the fertiliser treatment it was concluded that the N release in all the compost was lower than the crop demand.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"33 1","pages":"63 - 68"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79840792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/eaafj.v68i3.1787
J. Wamuongo, A. Esilaba, J. Miriti, J. N. Mwangi, S. Kimani
Mixed arable-livestock farming systems are common in central Kenya and manure from livestock is used as fertiliser in arable fields. However, increasing demographic pressure and intensification of agriculture has resulted in more continuous cultivation of arable lands without concomitant application of fertilisers. Continuous cultivation of land has resulted in accelerated soil nutrient depletion, decline in soil organic matter content, loss of physical structure and reduced crop productivity (Ikombo et al., 1994; Kilewe and Thomas, 1992).
{"title":"The Organic Matter and Nitrogen Status of Manure on Smallholder Farms in Central Kenya","authors":"J. Wamuongo, A. Esilaba, J. Miriti, J. N. Mwangi, S. Kimani","doi":"10.4314/eaafj.v68i3.1787","DOIUrl":"https://doi.org/10.4314/eaafj.v68i3.1787","url":null,"abstract":"Mixed arable-livestock farming systems are common in central Kenya and manure from livestock is used as fertiliser in arable fields. However, increasing demographic pressure and intensification of agriculture has resulted in more continuous cultivation of arable lands without concomitant application of fertilisers. Continuous cultivation of land has resulted in accelerated soil nutrient depletion, decline in soil organic matter content, loss of physical structure and reduced crop productivity (Ikombo et al., 1994; Kilewe and Thomas, 1992).","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"42 1","pages":"135 - 142"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89817928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-01DOI: 10.4314/EAAFJ.V68I4.1793
S. Ganesh, A. Khan, N. Senthil
High energy sorghums produce high alcohol content harvest with a considerable level of grain yield. Identification of superior hybrids with high alcohol content and grain yield is important (Selvi and Palnaisamy, 1987) for high-energy sorghum improvement. Ramalingam (1983) made genetic analysis of high energy sorghum for juice content and grain yield components. Selvi (1984) detected some of the superior cross combinations based on heterosis and combining ability studies. Assessment of combining ability for these traits will provide useful information for the selection of parents and hybrids based on general combining ability (gca) and specific combining ability (sca) effects. It also gives information on the nature of gene action governing the particular trait. The present study was conducted on 7 x 7 diallel cross for combining ability analysis to identify good combiners and superior for high energy.
{"title":"Identification of High Energy Sorghums by Combining Ability Studies","authors":"S. Ganesh, A. Khan, N. Senthil","doi":"10.4314/EAAFJ.V68I4.1793","DOIUrl":"https://doi.org/10.4314/EAAFJ.V68I4.1793","url":null,"abstract":"High energy sorghums produce high alcohol content harvest with a considerable level of grain yield. Identification of superior hybrids with high alcohol content and grain yield is important (Selvi and Palnaisamy, 1987) for high-energy sorghum improvement. Ramalingam (1983) made genetic analysis of high energy sorghum for juice content and grain yield components. Selvi (1984) detected some of the superior cross combinations based on heterosis and combining ability studies. Assessment of combining ability for these traits will provide useful information for the selection of parents and hybrids based on general combining ability (gca) and specific combining ability (sca) effects. It also gives information on the nature of gene action governing the particular trait. The present study was conducted on 7 x 7 diallel cross for combining ability analysis to identify good combiners and superior for high energy.","PeriodicalId":11421,"journal":{"name":"East African Agricultural and Forestry Journal","volume":"15 1","pages":"169 - 172"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72796037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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