Pardon Muchaonyerwa

Evaluation of human urine as a source of nutrients for selected vegetables and maize under tunnel house conditions in the Eastern Cape, South Africa:

The introduction of ecological sanitation (ECOSAN) toilets in South Africa has created opportunities for safer sanitation and recycling of human excreta, as fertilizers, in rural and peri-urban areas. A study was carried out to evaluate the fertilizer value of human urine (0 to 400 kg N ha—1) for maize and tomato, compared to urea, in a tunnel house. Dry matter yield of both maize and tomato, harvested at 9 and 10 weeks after planting, respectively, increased with increasing N rate (both as urine or urea) up to 200 kg N ha —1. Urea reduced soil electrical conductivity (EC) whereas urine increased it. Leaf tissue Na, in both crops, also increased with urine application. A follow-up study was carried out with two crops with contrasting sensitivity to salinity and using a wider range of N application (0 to 800 kg N ha—1). The results indicated increased root and leaf dry-matter yield of beetroot (tolerant to salinity) with increased urine rates up to the highest rate of 800 kg N ha—1 , whereas the leaf and root dry-matter yield of carrot, which is sensitive to salinity, peaked at the low urine application rate of 50 kg N ha— 1. Soil EC increased with urine application up to 4.64 and 13.35 mS cm—1, under beetroot and carrot, respectively. Generally the results showed that human urine compared well with urea as a source of N for crops but optimum rates depend on the sensitivity of the crops to soil salinity, which should be monitored where human urine is regularly used for fertilizing crops.

Effects of a precomposting step on the vermicomposting of dairy manure-waste paper mixtures

Thermophilic composting is being promoted as a means of sanitizing waste materials prior to vermicomposting. The precomposting duration is, however, critical to the success of the vermicomposting phase as it affects worm biomass. This study evaluated the effectiveness of different precomposting periods (0, 1, 2, 3 and 4 weeks) on the sanitization and vermicomposting of dairy manure—waste paper mixtures. The parameters measured were coliform bacteria and protozoa oocyst numbers, earthworm growth, as well as stabilization and nutrient content of vermicomposts. Over 95% of fecal coliforms, Escherichia coli and of E. coli 0157 were eliminated from the waste materials within 1 week of precomposting and total elimination of these and protozoan oocysts was achieved after 3 weeks of precomposting. Microbial biomass carbon and water soluble carbon of waste mixtures decreased with increase in precomposting time and impacted negatively on earthworm growth and subsequent stabilization of the dairy manure—paper waste mixtures. Vermicomposts from waste mixtures precomposted for over 2 weeks were less stabilized, less humified and had lower nutrient contents than vermicomposts from waste mixtures precomposted for 1 week or less. A precomposting period of 1 week was found to be ideal for the effective vermicomposting of dairy manure—waste paper mixtures.

Complementary nutrient effects of separately collected human faeces and urine on the yield and nutrient uptake of spinach (Spinacia oleracea)

A glasshouse experiment was conducted to evaluate the combined use of separately collected human faeces and urine as fertilizer for spinach (Spinacia oleracea) production. Seven human faeces N : urine N combinations (1 : 7 to 7 : 1) each supplying 200 kg N ha—1 were evaluated along with sole human faeces, sole urine, inorganic fertilizer and an unamended control. Complementary application of the two resources, human faeces and urine, increased fresh and dry matter yields only in treatments having high proportions of urine. Nitrogen uptake followed the same trend but the opposite trend occurred for P uptake indicating that urine was a better source of N whereas human faeces were the better source of P. Potassium uptake was not influenced by the two resources. The minimal improvement observed in the fertilizer value of human faeces when co-applied with urine suggested that co-application of the two resources may not give an added yield advantage when compared with sole human faeces.

Effects of cyanobacteria strains selected for their bioconditioning and biofertilization potential on maize dry matter and soil nitrogen status in a South African soil.

Abstract Some cyanobacteria strains have biofertilization and/or bioconditioning effects in soils as a result of their ability to fix dinitrogen or produce exocellular polysaccharides. The objective of the present study was to screen indigenous cyanobacteria strains with the potential to improve the N fertility and structural stability of degraded soils, and evaluate their ameliorative effectiveness in semiarid soils of the Eastern Cape, South Africa. Soils from Guquka, Hertzog and Qunu villages, and Fort Cox College were used in the screening study. The results showed that only three cyanobacteria strains (3g, 3v and 7e) out of 97 isolated strains were heterocystous, with appreciable nitrogenase activity and the ability to produce exocellular polysaccharides. Nostoc strains 3g and 3v had a greater ability to produce exocellular polysaccharides, but low potential to fix dinitrogen (4.7 and 1.3 nmol C2H4 μg−1 chl h−1, respectively). Strain 7e had the greatest ability to fix dinitrogen (16.1 nmol C2H4 μg−1 chl h−1), but produced fewer exocellular polysaccharides. The ability of strains 3g and 7e to influence maize dry matter (DM) and soil C and N contents was tested in a nitrogen-poor soil with Nostoc strain 9v as a reference strain. Potted soils with and without growing maize plants were inoculated with the different cyanobacteria strains in a glasshouse at a rate of 6 g m−2 soon after maize emergence. Harvesting and soil sampling were done 6 weeks after inoculation. Inoculation with strains 3g and 7e increased maize DM and N uptake significantly, on par with the reference strain. These increases were consistent with increases in nitrate-N observed at harvest time in inoculated cropped and non-cropped soils. Strain 7e resulted in greater increases in soil nitrate-N, tissue N and uptake than strain 3g, perhaps because of its greater ability to fix dinitrogen. Cropping with maize reduced soil total C and N, possibly owing to its negative effects on cyanobacteria establishment. These results suggest that indigenous cyanobacteria strains screened for greater N2-fixing ability have the potential to improve the productivity of N-poor soils in semiarid regions in South Africa.

Decomposition, Nitrogen, and Phosphorus Mineralization from Residues of Summer-Grown Cover Crops and Suitability for a Smallholder Farming System in South Africa

Cover crops, usually grown under conservation agriculture, may offer numerous benefits depending on the farming system. In this study the authors investigated residue decomposition, nitrogen (N) and phosphorus (P) release from mucuna (Mucuna pruriens) and sunhemp (Crotalaria juncea) as well as their uptake by maize in a farming system common in smallholder farms in South Africa. This was done through litterbag, laboratory incubation, and field studies. Sunhemp stems had 65% dry weight remaining after 132 days while just over 10% of mucuna and sunhemp leaves remained. There was no mineral contribution to maize growth by cover crops. However, in incubation studies, mucuna mineralized 60 mg N kg−1 and 3.2 mg P kg−1 and sunhemp mineralized 45 mg N kg−1 and 3.5 mg P kg−1. This suggested that weeds and/or leaching may have impacted negatively to nutrient flow from decaying cover crops species to maize during the long winter fallow period.

Effects of ensiling of Bacillus thuringiensis (Bt) maize (MON810) on degradation of the crystal 1Ab (Cry1Ab) protein and compositional quality of silage

The study investigated the degradation of the Bt protein (Cry1Ab) in Bt maize during ensiling and chemical composition of the silage. Two laboratory studies were conducted at the University of Fort Hare. One Bacillus thuringiensis (Bt) maize cultivar (DKC80-12B) and its isoline (DKC80-10) in the 2008/2009 study and two Bt maize cultivar (DKC61-25B and PAN6Q-321B) and their isolines (DKC61-24 and PAN6777) in the 2009/2010 study, were ensiled for 42 days and analyzed for ash-free dry matter, Cry1Ab protein, neutral detergent fiber, acid detergent fiber, acid detergent lignin and crude protein. Silage from two of the Bt maize varieties had lower ash-free dry matter than their near-isolines, while variety DKC61-25B was similar to its near-isoline. At least, 60% of the initial Cry1Ab protein concentration remained in the silage. Bt maize had higher neutral and acid detergent fiber than its isolines before ensiling and remained constant after ensiling in 2008/2009, but was neither influenced by ensiling nor variety in 2009/2010. Crude protein and acid detergent lignin in Bt maize silages were similar to those in silages derived from their near-isolines. The findings suggested that Bt maize will result in silage with similar chemical composition to that of non-Bt maize but a large proportion of the Cry1Ab protein persists.

Effect of pine bark goat manure medium on seedling growth and N, P, K concentration of various vegetables

Pine bark compost is the medium of choice for seedling growers in South Africa due to its availability, low cost and good physical properties. However, it is acidic, has low electrical conductivity (EC) and nutrient content such that fortification and liming is necessary. In a bid to improve the properties of pine bark compost, at a low cost, pine bark was co-composted with goat manure (PBG), and compared with commercial pine bark compost (PBCO) as a growing medium for vegetable amaranth, cabbage, tomato, and lettuce seedlings with and without Horticote (a slow release fertiliser). The water holding capacities of both PBCO and PBG media were higher than the minimum required but their air filled porosities were below optimum. Neither medium nor fertiliser levels had an effect on emergence of all the test crops. The different vegetable seedlings grew better in PBG than the PBCO medium. Addition of the slow-release fertiliser had similar positive effects on growth of seedlings grown on both media. Significant interactions between fertiliser and growing medium were observed in fresh weights of shoots for all the seedling crops evaluated. Results of this study revealed that PBG medium supported good seedling growth and could thus be a good substitute for PBCO as a growing medium. Use of a slow release fertiliser is highly encouraged as this can lower both nutrient losses through leaching and production costs.

Effects of relay inter-cropping summer cover crops with maize on cover crop biomass and maize yields in a warm-temperate region of South Africa : short communications

Little research attention has been given to growing summer cover crops as part of conservation agriculture systems. Three cover crops (sorghum [Sorghum bicolor], mucuna [Mucuna pruriens] and sunhemp [Crotalaria juncea]) were relay-intercropped into maize [Zea mays] 42 days after planting maize. Biomass yields, N uptake and maize yield were measured. In sole cropping, sorghum had the highest dry weight (11 t ha−1) followed by sunhemp (7.2 t ha−1) and mucuna (6.1 t ha−1). However, cover crop biomass yields dropped significantly (85% for sorghum, 70% for sunhemp and mucuna) when relay-intercropped into maize. Nitrogen uptake followed a similar pattern with mucuna having the highest N-uptake of 70 kg N ha−1 in relay-intercropping as compared to the > 250 kg N ha−1 in the sole cropping system. Maize biomass and grain yields were not affected by relay-intercropping cover crops. The low cover crop biomass yields in relay-intercropping may not be viable for sustainable conservation agriculture.

Effects of transgenic maize expressing the Cry1Ab protein (event MON810) on locally adapted earthworms in a sandy loam soil in the Central Eastern Cape, South Africa

This field study investigated effects of growing Bacillus thuringiensis (Bt) maize (MON810) on local earthworms in the Central Eastern Cape, South Africa. Two Bt maize cultivars (DKC61-25B and PAN6Q-321B) and their near-isolines (DKC61-24 and PAN6777) were grown in the 2009/2010 and 2010/2011 summer seasons. Earthworms were sampled after six, nine and eighteen weeks in 2009/2010 and after six, twelve and twenty-one weeks in the 2010/2011 season. The four maize treatments had similar earthworm counts, irrespective of sampling time, in both seasons. Sampling time had no effect in the 2009/2010 season, whereas the earthworm counts at 21 weeks after planting (WAP) were lower than the other two sampling times during the 2010/2011 season. The findings suggested that, at least in the short-term, growing Bt maize does not have negative effects on the numbers of the earthworms in the Central Eastern Cape, South Africa. Key words: Bacillus thuringiensis (Bt) maize, Cry1Ab protein, earthworm counts.