Evaluation and management of cover crop species and their effects on weed dynamics, soil fertility and maize (Zea mays L.) productivity under irrigation in the Eastern Cape Province, South Africa
- Authors: Murungu, Farayi Solomon
- Date: 2010
- Subjects: Crops -- South Africa , Conservation of natural resources -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape , Soil percolation -- South Africa -- Eastern Cape , Soil permeability -- South Africa -- Eastern Cape , Irrigation farming -- South Africa -- Eastern Cape , Corn -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Crop Science)
- Identifier: vital:11866 , http://hdl.handle.net/10353/335 , Crops -- South Africa , Conservation of natural resources -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape , Soil percolation -- South Africa -- Eastern Cape , Soil permeability -- South Africa -- Eastern Cape , Irrigation farming -- South Africa -- Eastern Cape , Corn -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape
- Description: The current interest in conservation agriculture (CA) technologies is a result of the need to reduce excessive land degradation in most crop producing areas as well as to enhance sustainable food production. Cover crops that are usually grown under CA to provide soil cover, may offer secondary benefits, depending on the farming system. The concept of growing cover crops is a relatively new phenomenon to smallholder farmers. Production of large biomass yields and weed suppression from cover crops were major challenges affecting success and uptake of CA technologies by smallholder irrigation farmers. Coupled with this, low soil fertility limit maize productivity and reduce water use efficiency on smallholder irrigation schemes in what is largely a water strained agro-ecology in South Africa. While cover cropping can increase maize productivity, benefits of different types of mulch are not well understood, leading to challenges in selecting the most appropriate cover crop species to grow in the Eastern Cape Province (EC) of South Africa (SA) which has a warm temperate climate. With respect to any new technology, smallholder farmers are more interested in the economic benefits. Cover crops have been defined as leguminous or non-leguminous plants used for ground cover in various temporal and special configurations used in crop or animal production systems. The purpose of these cover crops is to improve on or more of the following: soil erosion, availability and cycling of N, P, K, Ca and other nutrients, soil moisture and water infiltration, and weed or pest control (Eilitta et al., 2004).. Improvement of animal or human diet may be additional goals. This definition accommodates diverse systems which may include intercrop and sole-cropping systems. In the Eastern Cape Province of South Africa, a government initiative has promoted the growing of winter cover crops in smallholder irrigation schemes (Allwood, 2006). In other parts of Africa, legume food crops have been simultaneously grown with cereal staples to improve both soil cover and human diet (Eilitta et al., 2004). Winter experiments were undertaken in 2007 and 2008 to evaluate biomass accumulation, C and N uptake, weed suppression and response to fertilization. Winter cover crops planted included; oats (Avena sativa), grazing vetch (Vicia dasycarpa), faba bean (Vicia faba), forage peas (Pisum sativum) and lupin (Lupinus angustifolius). After cover crops were terminated, the effects of residues on weeds, fertility, moisture conservation and maize productivity were undertaken in the 2007/08 and 2008/09 summer seasons. Field studies were also done in the 2007/08 and 2008/09 summer seasons to investigate effects of strip intercropping patterns (3:2; 4:2; and 6:2 patterns) of maize (cv. PAN 6479) with mucuna (Mucuna pruriens) or sunnhemp (Crotalaria juncea) on maize productivity and summer cover crop biomass production. In a separate experiment effects of relay intercropping sunnhemp, mucuna and sorghum (Sorghum bicolor) on biomass accumulation and maize productivity were investigated. Decomposition, N and P release from both winter cover crops and summer cover crops were also assessed in laboratory incubation experiments. Oats, grazing vetch and forage peas cover crops produced mean dry mass of 13873 kg/ha, 8945.5 kg/ha and 11073 kg/ha, respectively, while lupin had the lowest dry mass of 1226 kg/ha over the two seasons. Oats responded to fertilization while, there was little or no response from the other winter cover crops. Oats and grazing vetch also reduced weed density by 90 % and 80 % respectively while lupin only reduced weed density by 23 % in relation to the control plots. Nitrogen uptake was 254 kg N/ha for oats while it was 346 kg N /ha for grazing vetch. In the subsequent summer season, grazing vetch and forage pea residues significantly (P < 0.01) improved soil inorganic N. Oat and grazing vetch residues significantly (P < 0.05) reduced weed dry masss and weed species diversity compared to plots with lupin residues and the control. Lack of maize fertilization tended to reduce maize yields but not for maize grown on grazing vetch residues. From an economic perspective, grazing vetch resulted in the highest returns. Decomposition of winter cover crops was much faster for grazing vetch followed by forage peas and lastly oats. Oats had 40 % ash free dry mass remaining after 124 days while grazing vetch and forage peas had 7 % and 16 % respectively. Maximum net mineralized N and P were greater for grazing vetch (84.8 mg N/kg; 3.6 mg P/kg) compared to forage peas (66.3 mg N/kg; 2.7 mg P/ha) and oats (13.7 mg N/kg; 2.8 mg P/kg). In the strip intercropping trials, sunnhemp achieved the highest biomass yield of 4576 kg/ha in the 3:2 pattern while mucuna achieved 1897 kg/ha for the same strip pattern. The 3:2 strip intercropping pattern slightly depressed yields, however, yield reduction was more pronounced in the first season where water stress was experienced. Growing maize on previous cover crop strips failed to increase maize productivity probably due to weed growth during the fallow reducing mineral N in these strips. Decomposition was faster in sunnhemp leaves and mucuna compared to sunnhemp stems. Sunnhemp stems had about 65 % of ash free dry mass remaining after the end of the experiment at 132 days while just over 10 % of mucuna and sunnhemp leaves still remained. Mucuna mineralized 60 mg N/kg and 3.2 mg P/kg and sunnhemp mineralized 45 mg N/kg and 3.5 mg P/kg. Relay intercropping did not significantly (P > 0.05) affect maize biomass and grain yield. Sorghum experienced the largest drop in biomass when relay-intercropped with maize. Mucuna resulted in the highest N uptake (271 kg N/ha) in sole cropping while sorghum had the lowest (88 kg N/ha). Grazing vetch results in high biomass yields with minimal fertilizer application in a warm-temperate climate. Grazing vetch mulch is also the most cost effective mulch for better early weed control, improving soil mineral N status, water conservation and ultimately enhanced maize productivity in smallholder irrigation maize-based systems. The 3:2 pattern maximizes summer cover crop biomass yields compared to the 6:2 and 4:2 patterns. However, the 3:2 pattern may slightly depress yields in a water stressed environment. Relay intercropping mucuna, sunnhemp and sorghum into a maize crop at 42 days after maize sowing has no effect on maize productivity while cover crop biomass yields are low. Having a long winter fallow period after maize harvesting, a common practice in the study area, reduces the positive impact of legume cover crops on soil mineral N. Results suggest that winter cover crops may result in weed control, soil fertility and maize yield improvement benefits while a long fallow period may cancel-out these benefits for summer cover crops. Grazing vetch is a cost effective cover crop that produces high maize yields with minimal fertilizer input. Maize growing on oat mulch requires more fertilizer application than crops growing on grazing vetch mulch. Conservation agriculture systems in which summer cover crops are grown alongside the maize crop with a long winter fallow period do not produce the intended CA benefits.
- Full Text:
- Date Issued: 2010
- Authors: Murungu, Farayi Solomon
- Date: 2010
- Subjects: Crops -- South Africa , Conservation of natural resources -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape , Soil percolation -- South Africa -- Eastern Cape , Soil permeability -- South Africa -- Eastern Cape , Irrigation farming -- South Africa -- Eastern Cape , Corn -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Crop Science)
- Identifier: vital:11866 , http://hdl.handle.net/10353/335 , Crops -- South Africa , Conservation of natural resources -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape , Soil percolation -- South Africa -- Eastern Cape , Soil permeability -- South Africa -- Eastern Cape , Irrigation farming -- South Africa -- Eastern Cape , Corn -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape
- Description: The current interest in conservation agriculture (CA) technologies is a result of the need to reduce excessive land degradation in most crop producing areas as well as to enhance sustainable food production. Cover crops that are usually grown under CA to provide soil cover, may offer secondary benefits, depending on the farming system. The concept of growing cover crops is a relatively new phenomenon to smallholder farmers. Production of large biomass yields and weed suppression from cover crops were major challenges affecting success and uptake of CA technologies by smallholder irrigation farmers. Coupled with this, low soil fertility limit maize productivity and reduce water use efficiency on smallholder irrigation schemes in what is largely a water strained agro-ecology in South Africa. While cover cropping can increase maize productivity, benefits of different types of mulch are not well understood, leading to challenges in selecting the most appropriate cover crop species to grow in the Eastern Cape Province (EC) of South Africa (SA) which has a warm temperate climate. With respect to any new technology, smallholder farmers are more interested in the economic benefits. Cover crops have been defined as leguminous or non-leguminous plants used for ground cover in various temporal and special configurations used in crop or animal production systems. The purpose of these cover crops is to improve on or more of the following: soil erosion, availability and cycling of N, P, K, Ca and other nutrients, soil moisture and water infiltration, and weed or pest control (Eilitta et al., 2004).. Improvement of animal or human diet may be additional goals. This definition accommodates diverse systems which may include intercrop and sole-cropping systems. In the Eastern Cape Province of South Africa, a government initiative has promoted the growing of winter cover crops in smallholder irrigation schemes (Allwood, 2006). In other parts of Africa, legume food crops have been simultaneously grown with cereal staples to improve both soil cover and human diet (Eilitta et al., 2004). Winter experiments were undertaken in 2007 and 2008 to evaluate biomass accumulation, C and N uptake, weed suppression and response to fertilization. Winter cover crops planted included; oats (Avena sativa), grazing vetch (Vicia dasycarpa), faba bean (Vicia faba), forage peas (Pisum sativum) and lupin (Lupinus angustifolius). After cover crops were terminated, the effects of residues on weeds, fertility, moisture conservation and maize productivity were undertaken in the 2007/08 and 2008/09 summer seasons. Field studies were also done in the 2007/08 and 2008/09 summer seasons to investigate effects of strip intercropping patterns (3:2; 4:2; and 6:2 patterns) of maize (cv. PAN 6479) with mucuna (Mucuna pruriens) or sunnhemp (Crotalaria juncea) on maize productivity and summer cover crop biomass production. In a separate experiment effects of relay intercropping sunnhemp, mucuna and sorghum (Sorghum bicolor) on biomass accumulation and maize productivity were investigated. Decomposition, N and P release from both winter cover crops and summer cover crops were also assessed in laboratory incubation experiments. Oats, grazing vetch and forage peas cover crops produced mean dry mass of 13873 kg/ha, 8945.5 kg/ha and 11073 kg/ha, respectively, while lupin had the lowest dry mass of 1226 kg/ha over the two seasons. Oats responded to fertilization while, there was little or no response from the other winter cover crops. Oats and grazing vetch also reduced weed density by 90 % and 80 % respectively while lupin only reduced weed density by 23 % in relation to the control plots. Nitrogen uptake was 254 kg N/ha for oats while it was 346 kg N /ha for grazing vetch. In the subsequent summer season, grazing vetch and forage pea residues significantly (P < 0.01) improved soil inorganic N. Oat and grazing vetch residues significantly (P < 0.05) reduced weed dry masss and weed species diversity compared to plots with lupin residues and the control. Lack of maize fertilization tended to reduce maize yields but not for maize grown on grazing vetch residues. From an economic perspective, grazing vetch resulted in the highest returns. Decomposition of winter cover crops was much faster for grazing vetch followed by forage peas and lastly oats. Oats had 40 % ash free dry mass remaining after 124 days while grazing vetch and forage peas had 7 % and 16 % respectively. Maximum net mineralized N and P were greater for grazing vetch (84.8 mg N/kg; 3.6 mg P/kg) compared to forage peas (66.3 mg N/kg; 2.7 mg P/ha) and oats (13.7 mg N/kg; 2.8 mg P/kg). In the strip intercropping trials, sunnhemp achieved the highest biomass yield of 4576 kg/ha in the 3:2 pattern while mucuna achieved 1897 kg/ha for the same strip pattern. The 3:2 strip intercropping pattern slightly depressed yields, however, yield reduction was more pronounced in the first season where water stress was experienced. Growing maize on previous cover crop strips failed to increase maize productivity probably due to weed growth during the fallow reducing mineral N in these strips. Decomposition was faster in sunnhemp leaves and mucuna compared to sunnhemp stems. Sunnhemp stems had about 65 % of ash free dry mass remaining after the end of the experiment at 132 days while just over 10 % of mucuna and sunnhemp leaves still remained. Mucuna mineralized 60 mg N/kg and 3.2 mg P/kg and sunnhemp mineralized 45 mg N/kg and 3.5 mg P/kg. Relay intercropping did not significantly (P > 0.05) affect maize biomass and grain yield. Sorghum experienced the largest drop in biomass when relay-intercropped with maize. Mucuna resulted in the highest N uptake (271 kg N/ha) in sole cropping while sorghum had the lowest (88 kg N/ha). Grazing vetch results in high biomass yields with minimal fertilizer application in a warm-temperate climate. Grazing vetch mulch is also the most cost effective mulch for better early weed control, improving soil mineral N status, water conservation and ultimately enhanced maize productivity in smallholder irrigation maize-based systems. The 3:2 pattern maximizes summer cover crop biomass yields compared to the 6:2 and 4:2 patterns. However, the 3:2 pattern may slightly depress yields in a water stressed environment. Relay intercropping mucuna, sunnhemp and sorghum into a maize crop at 42 days after maize sowing has no effect on maize productivity while cover crop biomass yields are low. Having a long winter fallow period after maize harvesting, a common practice in the study area, reduces the positive impact of legume cover crops on soil mineral N. Results suggest that winter cover crops may result in weed control, soil fertility and maize yield improvement benefits while a long fallow period may cancel-out these benefits for summer cover crops. Grazing vetch is a cost effective cover crop that produces high maize yields with minimal fertilizer input. Maize growing on oat mulch requires more fertilizer application than crops growing on grazing vetch mulch. Conservation agriculture systems in which summer cover crops are grown alongside the maize crop with a long winter fallow period do not produce the intended CA benefits.
- Full Text:
- Date Issued: 2010
Analysis of decision making in smallholder irrigation practice: a case study of Shiloh and Zanyokwe irrigation schemes in Central Eastern Cape, South Africa
- Authors: Isaac, Agholor Azikiwe
- Subjects: Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11215 , http://hdl.handle.net/10353/d1019766 , Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Description: The study was conducted in Zanyokwe and Shiloh smallholder irrigation schemes located in Eastern Cape Province at Amathole and Chris Hani districts respectively. The choice of Zanyokwe and Shiloh smallholder irrigation scheme for this study is mainly supported by the fact that it had a substantial level of crop farming activity taking place especially at Zanyokwe while the Shiloh smallholder irrigation specialises dairy farming. The study examined decision making in smallholder irrigation practice with particular reference to Shiloh and Zanyokwe irrigation schemes. The general objective of the thesis was to analyse and model the determinants of SIS farmer‟s decision making. The specific objectives of the study are as follows: to investigate the determinants of decision making among smallholder irrigation farmers; to examine the relationship between household and farm characteristics and institutional factors that explain decision making in smallholder irrigation scheme; assess the contribution of smallholder irrigation farming to household food security; and determine the production and marketing constraints of smallholder farmers‟ in both schemes. The theoretical and conceptual framework of the study gave a detailed discussion on the determinants of decision making of households. The theories used to understand household behaviour under different assumptions were variously discussed. Comprehensive illustrations of analytical framework of the study were also conceptualised. This study used a survey design, quantitative and qualitative research methodologies involving the use of questionnaires and focus group discussions. The data was coded and analysed using the Statistical Package for Social Science (SPSS). However, frequencies, percentages, bar and pie chart was also computed to describe the data. In consideration of the conceptual framework of the study, the agricultural household model was adopted to analyse smallholder farmer‟s household decision making. Twenty one explanatory variables identified in the conceptual framework of the study were discussed and some of these identified variables were incorporated into the model. The logistic regression model was used as a method of analysis because it can estimate the probability of a certain event occurring and it accommodates a lot of variables which can be ranked in order to illustrate which variables are significant. In the binary logistic model used, seven variables (farm experience, size of farmland, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant effect on influencing household decision making in Shiloh smallholder irrigation scheme, while five variables (gender, age, education, road distance and extension access) were not significant. Of the seven significant variables, four had positive signs (land rights/PTO, water sufficiency and market information); which means that an increase in either of these variables may be associated with an increase in household decision making in Shiloh. The other three predictor variables (farm experience, farm asset and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. In Zanyokwe, six variables (farm experience, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant impact on influencing household decision making, while six variables (gender, age, education, size of farm land, road distance and extension access) were not significant. Of the six significant variables, two had positive signs (water sufficiency and farm asset); which means that an increase in either of these variables may be associated with an increase in household decision making in Zanyokwe. The other four predictor variables (farm experience, land rights/PTO, market information and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. The study concludes that smallholder agriculture is essential for employment generation and food security of households. It is apparent that household food security will not be achieved without giving attention to the role played by smallholders‟ farmers in South Africa. It is pertinent to promulgate an efficient policy programme to address the diversity of smallholders‟ situations and identify the main constraints on investment. Therefore, all spheres of government, the private sector and NGOs should consider investment in smallholder agriculture through coordinated strategies and political support. This study also recommends that government should develop a strategic Smallholder Investment Plan which would improve investments in smallholder agriculture.
- Full Text:
- Authors: Isaac, Agholor Azikiwe
- Subjects: Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11215 , http://hdl.handle.net/10353/d1019766 , Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Description: The study was conducted in Zanyokwe and Shiloh smallholder irrigation schemes located in Eastern Cape Province at Amathole and Chris Hani districts respectively. The choice of Zanyokwe and Shiloh smallholder irrigation scheme for this study is mainly supported by the fact that it had a substantial level of crop farming activity taking place especially at Zanyokwe while the Shiloh smallholder irrigation specialises dairy farming. The study examined decision making in smallholder irrigation practice with particular reference to Shiloh and Zanyokwe irrigation schemes. The general objective of the thesis was to analyse and model the determinants of SIS farmer‟s decision making. The specific objectives of the study are as follows: to investigate the determinants of decision making among smallholder irrigation farmers; to examine the relationship between household and farm characteristics and institutional factors that explain decision making in smallholder irrigation scheme; assess the contribution of smallholder irrigation farming to household food security; and determine the production and marketing constraints of smallholder farmers‟ in both schemes. The theoretical and conceptual framework of the study gave a detailed discussion on the determinants of decision making of households. The theories used to understand household behaviour under different assumptions were variously discussed. Comprehensive illustrations of analytical framework of the study were also conceptualised. This study used a survey design, quantitative and qualitative research methodologies involving the use of questionnaires and focus group discussions. The data was coded and analysed using the Statistical Package for Social Science (SPSS). However, frequencies, percentages, bar and pie chart was also computed to describe the data. In consideration of the conceptual framework of the study, the agricultural household model was adopted to analyse smallholder farmer‟s household decision making. Twenty one explanatory variables identified in the conceptual framework of the study were discussed and some of these identified variables were incorporated into the model. The logistic regression model was used as a method of analysis because it can estimate the probability of a certain event occurring and it accommodates a lot of variables which can be ranked in order to illustrate which variables are significant. In the binary logistic model used, seven variables (farm experience, size of farmland, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant effect on influencing household decision making in Shiloh smallholder irrigation scheme, while five variables (gender, age, education, road distance and extension access) were not significant. Of the seven significant variables, four had positive signs (land rights/PTO, water sufficiency and market information); which means that an increase in either of these variables may be associated with an increase in household decision making in Shiloh. The other three predictor variables (farm experience, farm asset and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. In Zanyokwe, six variables (farm experience, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant impact on influencing household decision making, while six variables (gender, age, education, size of farm land, road distance and extension access) were not significant. Of the six significant variables, two had positive signs (water sufficiency and farm asset); which means that an increase in either of these variables may be associated with an increase in household decision making in Zanyokwe. The other four predictor variables (farm experience, land rights/PTO, market information and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. The study concludes that smallholder agriculture is essential for employment generation and food security of households. It is apparent that household food security will not be achieved without giving attention to the role played by smallholders‟ farmers in South Africa. It is pertinent to promulgate an efficient policy programme to address the diversity of smallholders‟ situations and identify the main constraints on investment. Therefore, all spheres of government, the private sector and NGOs should consider investment in smallholder agriculture through coordinated strategies and political support. This study also recommends that government should develop a strategic Smallholder Investment Plan which would improve investments in smallholder agriculture.
- Full Text:
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