Pearson Ns Mnkeni

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.

Tillage and crop rotation effects on carbon sequestration and aggregate stability in two contrasting soils at the Zanyokwe Irrigation Scheme, Eastern Cape province, South Africa

Intensive tillage and monocropping have adversely affected the quality of soils in South Africa through accelerated loss of soil organic matter. Two clay loam soils, a Bonheim at Burnshill and a Shortlands at Lenye, at the Zanyokwe Irrigation Scheme in the Eastern Cape province were used to evaluate the short-term effects of tillage and crop rotations on carbon sequestration and aggregate stability under sprinkler-irrigated crop production. A split-plot arrangement of treatments in a randomised complete block design was used with tillage as the main plots and crop rotations as subplots. Conventional tillage (CT) was compared to no-till (NT) under maize–fallow–maize (MFM), maize– wheat–maize (MWM) and maize–oat–maize (MOM) rotations. Carbon sequestration was monitored by measuring changes in soil organic carbon (SOC) and the stability index (SI) was used for monitoring aggregate stability. No-till had inconsistent effects on SOC relative to CT but resulted in improved soil SI on both soils, especially on the Shortlands soil. The MOM rotation enhanced SOC relative to the MWM and MFM rotations on both the Bonheim and Shortlands soils. Across tillage practices, the MOM rotation significantly increased the soil aggregate SI compared with the MWM and MFM rotations on the Shortlands and to a lesser extent on the Bonheim soils. Scanning electron microscopy revealed that soil aggregates under MOM had dense organic coatings and bridges compared with the MFM rotation, indicating the positive effect of carbon sequestration on aggregate stability. Generally, the results indicated that, in the short term, cover crops, especially oats, have greater influence on SOC accumulation and aggregate stability than tillage, irrespective of soil type.

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.

Sensitivity of selected chemical and biological soil quality parameters to tillage and rotational cover cropping at the Zanyokwe Irrigation Scheme, South Africa

Sustainable management of soils requires knowledge of the impact of agronomic practices such as tillage and crop rotation on soil quality. The objective of this study was to identify soil chemical and biological soil attributes with high sensitivity to tillage and rotational cover cropping practices on two sandy clay loam soils, a Bonheim at Burnshill and a Shortlands at Lenye, in the Zanyokwe Irrigation Scheme, Eastern Cape, South Africa. Treatments were no tillage, conventional tillage and three crop rotations involving maize–fallow–maize, maize–wheat–maize and maize–oat–maize. Principal component analysis was used to isolate the soil chemical and biological parameters that were most altered by tillage and crop rotations, while hierarchical cluster analysis was used to discriminate the crop rotation effects. Results showed that soil microbial biomass nitrogen, mineralisable nitrogen, and extractable phosphorus were the properties most altered by tillage and crop rotations. The soil properties that were most sensitive to tillage and crop rotations were those most influenced by organic matter inputs. The maize–wheat–maize and maize–oat– maize rotations were clustered together, indicating the similarity of their positive impact on soil quality.

Spatial variability of selected soil micronutrients under smallholder crop production in Zanyokwe, Eastern Cape, South Africa

Understanding spatial variability of soil nutrients, including that of micronutrients, is important for establishing best management practices in smallholder crop production. The objective of this study was to determine the status and spatial variability of potentially available zinc (Zn), copper (Cu), manganese (Mn) and iron (Fe) for selective management at Zanyokwe Irrigation Scheme. Soil samples were collected from the 0–20 cm depth on 50 m × 50 m grids and coordinates of the sampling points were recorded using a global positioning system (GPS). The samples were analysed for Zn, Cu, Mn and Fe after extraction with EDTA. The GPS coordinates and corresponding micronutrient values were interpolated using simple kriging to produce continuous raster surfaces, which were then reclassified, using prescribed limits, to produce soil micronutrient maps. Zinc was deficient and exhibited the highest spatial variability, within short distances. There was limited spatial variability of Cu, Mn and Fe. The study highlighted the need for the creation of management zones for Zn availability. Field studies are recommended to establish the extent to which Zn is limiting yields and nutritional quality of crops grown at the scheme.