Cover crop biomass production and effects on weeds and soil fertility in a maize-based conservation agriculture system
- Authors: Muzangwa, Lindah
- Date: 2011
- Subjects: Cover crops -- South Africa -- Eastern Cape , Biomass energy -- South Africa -- Eastern Cape , Weeds -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape , Corn -- Yields -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Crop Science)
- Identifier: vital:11862 , http://hdl.handle.net/10353/484 , Cover crops -- South Africa -- Eastern Cape , Biomass energy -- South Africa -- Eastern Cape , Weeds -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape , Corn -- Yields -- South Africa -- Eastern Cape
- Description: Low cover crop biomass production is a major obstacle to the success of conservation agriculture currently promoted as panacea to the inherent problem of soil erosion and loss of soil productivity in the Eastern Cape (EC). Therefore, this study evaluated cover crop management strategies for optimizing biomass production for better soil cover, soil nitrogen (N) and phosphorus (P) fertility, weed control and maize yields. The strategies tested are cover crop bicultures, selection of an adapted lupin cultivar and seeding rate, and the feasibility of rain fed winter cover cropping. The cover crop experiments were carried in rotation with summer maize between the winter of 2009 and summer of 2010/2011. Biculture trial was carried out by seeding oat (Avena sativa) and vetch (Vicia dasycarpa) at three mixture ratios and as sole crops under irrigation. On a separate irrigated trial, two lupin cultivars (Lupinus angustifolius var Mandelup & Qualinock) were seeded to a range of seeding rate, 40 to 220 kg ha-1. To study the feasibility of rain fed winter cover cropping, oat, vetch, rye (Lolium multiflorum), barley (Hordeum vulgare), radish (Raphanus sativa) and triticale (Triticale secale) were relayed into a maize crop in February, March and April of 2010. The irrigated trials were followed with SC701 maize cultivar, whilst the rain fed trial was followed with DKC61-25 maize cultivar. Bicultures gave higher cover crop biomass than sole vetch, increasing with an increase in the oat component of the mixture. Increased N and P uptake was observed with bicultures compared to sole oat, however, the levels were comparable to sole vetch. Sole vetch increased soil inorganic N and P at maize planting, whilst the slow decomposition by sole oat residue resulted in mineral lock up. Bicultured cover crop residues had intermediate decomposition rates and resulted in optimum levels of inorganic N and P for prolonged periods compared to sole crops. Weed suppression by the bicultures was comparable to sole cover crops. Biculturing technology significantly (P<0.05) increased maize grain yield compared to sole oat and the yields were comparable to those from sole vetch. For lupins, 206 kg ha-1 seeding rate gave the optimum biomass yield. Weed dry weights in both cover crop and maize crop decreased with an increase in lupin biomass. Comparable soil total N and inorganic P values at maize planting, were observed from plots planted to 120, 180 and 220 kg ha-1. Maize grain yield increased with an increase in lupin seeding rate. The study on rain fed winter cover cropping had most cover crop species’ biomass decreasing with each delay in planting except for radish, which increased. Vetch produced the highest amounts of biomass from February and March planting whilst radish had the highest biomass in April planting. The two species resulted in the greatest N improvement compared to the other species. Regardless of the grazing, the grass specie residues managed to persist to the next cropping season and the residue remaining were comparable to that of radish and vetch. Late-planted cover crops had the greatest residue remaining than early-planted, as a result, April planted cover crops provided better weed suppression than March and April planted. Vetch provided the highest maize grain yield (4005 kg ha-1) whilst all other species tested had comparable grain yields. The results suggested that bicultures could be grown to give sufficient biomass for both weed suppression and soil fertility improvement. Furthermore, increasing lupin plant densities improve its function as a cover crop with respect to weed suppression, soil fertility improvement and maize yields. The study also showed that for dry land systems, February and March planted vetch and April planted radish can provide the greatest biomass and maize yield improvement.
- Full Text:
- Date Issued: 2011
- Authors: Muzangwa, Lindah
- Date: 2011
- Subjects: Cover crops -- South Africa -- Eastern Cape , Biomass energy -- South Africa -- Eastern Cape , Weeds -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape , Corn -- Yields -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Crop Science)
- Identifier: vital:11862 , http://hdl.handle.net/10353/484 , Cover crops -- South Africa -- Eastern Cape , Biomass energy -- South Africa -- Eastern Cape , Weeds -- South Africa -- Eastern Cape , Soil fertility -- South Africa -- Eastern Cape , Corn -- Yields -- South Africa -- Eastern Cape
- Description: Low cover crop biomass production is a major obstacle to the success of conservation agriculture currently promoted as panacea to the inherent problem of soil erosion and loss of soil productivity in the Eastern Cape (EC). Therefore, this study evaluated cover crop management strategies for optimizing biomass production for better soil cover, soil nitrogen (N) and phosphorus (P) fertility, weed control and maize yields. The strategies tested are cover crop bicultures, selection of an adapted lupin cultivar and seeding rate, and the feasibility of rain fed winter cover cropping. The cover crop experiments were carried in rotation with summer maize between the winter of 2009 and summer of 2010/2011. Biculture trial was carried out by seeding oat (Avena sativa) and vetch (Vicia dasycarpa) at three mixture ratios and as sole crops under irrigation. On a separate irrigated trial, two lupin cultivars (Lupinus angustifolius var Mandelup & Qualinock) were seeded to a range of seeding rate, 40 to 220 kg ha-1. To study the feasibility of rain fed winter cover cropping, oat, vetch, rye (Lolium multiflorum), barley (Hordeum vulgare), radish (Raphanus sativa) and triticale (Triticale secale) were relayed into a maize crop in February, March and April of 2010. The irrigated trials were followed with SC701 maize cultivar, whilst the rain fed trial was followed with DKC61-25 maize cultivar. Bicultures gave higher cover crop biomass than sole vetch, increasing with an increase in the oat component of the mixture. Increased N and P uptake was observed with bicultures compared to sole oat, however, the levels were comparable to sole vetch. Sole vetch increased soil inorganic N and P at maize planting, whilst the slow decomposition by sole oat residue resulted in mineral lock up. Bicultured cover crop residues had intermediate decomposition rates and resulted in optimum levels of inorganic N and P for prolonged periods compared to sole crops. Weed suppression by the bicultures was comparable to sole cover crops. Biculturing technology significantly (P<0.05) increased maize grain yield compared to sole oat and the yields were comparable to those from sole vetch. For lupins, 206 kg ha-1 seeding rate gave the optimum biomass yield. Weed dry weights in both cover crop and maize crop decreased with an increase in lupin biomass. Comparable soil total N and inorganic P values at maize planting, were observed from plots planted to 120, 180 and 220 kg ha-1. Maize grain yield increased with an increase in lupin seeding rate. The study on rain fed winter cover cropping had most cover crop species’ biomass decreasing with each delay in planting except for radish, which increased. Vetch produced the highest amounts of biomass from February and March planting whilst radish had the highest biomass in April planting. The two species resulted in the greatest N improvement compared to the other species. Regardless of the grazing, the grass specie residues managed to persist to the next cropping season and the residue remaining were comparable to that of radish and vetch. Late-planted cover crops had the greatest residue remaining than early-planted, as a result, April planted cover crops provided better weed suppression than March and April planted. Vetch provided the highest maize grain yield (4005 kg ha-1) whilst all other species tested had comparable grain yields. The results suggested that bicultures could be grown to give sufficient biomass for both weed suppression and soil fertility improvement. Furthermore, increasing lupin plant densities improve its function as a cover crop with respect to weed suppression, soil fertility improvement and maize yields. The study also showed that for dry land systems, February and March planted vetch and April planted radish can provide the greatest biomass and maize yield improvement.
- Full Text:
- Date Issued: 2011
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
Evaluation and mapping of the spatial variability of soil fertility at Zanyokwe Irrigation Scheme in the Eastern Cape, South Africa
- Authors: Manyevere, Alen
- Date: 2010
- Subjects: Soil surveys -- South Africa -- Eastern Cape , Irrigation farming -- South Africa , Soil fertility -- South Africa -- Eastern Cape , Soils -- Analysis , Soils -- Testing , Crop yields , Soils Classification
- Language: English
- Type: Thesis , Masters , MSc Agric (Soil Science)
- Identifier: vital:11176 , http://hdl.handle.net/10353/d1001019 , Soil surveys -- South Africa -- Eastern Cape , Irrigation farming -- South Africa , Soil fertility -- South Africa -- Eastern Cape , Soils -- Analysis , Soils -- Testing , Crop yields , Soils Classification
- Full Text: false
- Date Issued: 2010
- Authors: Manyevere, Alen
- Date: 2010
- Subjects: Soil surveys -- South Africa -- Eastern Cape , Irrigation farming -- South Africa , Soil fertility -- South Africa -- Eastern Cape , Soils -- Analysis , Soils -- Testing , Crop yields , Soils Classification
- Language: English
- Type: Thesis , Masters , MSc Agric (Soil Science)
- Identifier: vital:11176 , http://hdl.handle.net/10353/d1001019 , Soil surveys -- South Africa -- Eastern Cape , Irrigation farming -- South Africa , Soil fertility -- South Africa -- Eastern Cape , Soils -- Analysis , Soils -- Testing , Crop yields , Soils Classification
- Full Text: false
- Date Issued: 2010
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