Simeon A. Materechera

The effectiveness of lime, chicken manure and leaf litter ash in ameliorating acidity in a soil previously under black wattle (Acacia mearnsii) plantation.

There are about 130,000 hectares of land in South Africa that have been under black wattle plantation for a long time and whose soils have become more acidic than those from contiguous land without the tree. This incubation study investigated the effectiveness of lime, chicken manure and leaf litter ash to ameliorate the soil acidity. Lime and chicken manure were applied in pots at rates equivalent to 0, 5, 10 and 20 Mg ha(-1) while ash was applied at 0, 3 and 5 Mg ha(-1). In comparison to the control, the application of all the three amendments caused significant increases in soil pH(KCL) (4.1-5.6) and reduced the exchangeable acidity. The liming effectiveness of the amendments varied with rate and type of amendment and were in the order: lime > chicken manure > ash. A similar trend was evident in the concentration of exchangeable bases (Ca, Mg and K) in the soil. The effectiveness of ash and chicken manure as liming material was 0.12 and 0.26 respectively compared to lime. The difference in liming effect between ash and chicken manure was related to their alkalinity concentration. It was concluded that both amendments have the potential to be used as liming materials and merit further field evaluation.

Influence of land-use on properties of a ferralitic soil under low external input farming in southeastern Swaziland

An assessment of changes in soil properties associated with land-use and management practices is vital for the selection and establishment of appropriate sustainable practices under different agroecosystems. This study compared soil properties between land located on an abandoned kraal site (KS), under fallow (FL) and one that was continuously cropped to maize (CC) for over 12 years. Aggregation and aggregate stability as measured by both dry and wet sieving showed large differences between land-use systems. The soil under CC had a higher proportion (26.4%) of micro aggregates (<0.25 mm) compared with that of FL (10.1%) and KS (6.9%). The dry mean weight diameter (DMWD) was larger in KS (3.03 mm) than in FL (2.17 mm) and CC (1.38 mm). Soil aggregates in CC were the least stable with a wet mean weight diameter (WMWD) of (1.61 mm) compared with those of FL (2.18 mm) and KS (2.89 mm). Reduced stability of aggregates in CC is likely due to the lower organic carbon content of soil in this land-use (1.7%) compared with that of FL (2.5%) and KS (3.2%). The soil under KS had lower bulk density (BD), penetration resistance (PR) and aggregate tensile strength (ATS) than that of FL and CC. Soil moisture content (MC) and available water capacity (AWC) showed an opposite trend. The soil in KS had a higher concentration of total N (TN), available P and exchangeable K, Ca, Mg and Zn. Soil on CC, on the other hand, had a higher concentration of Mn than that from FS and KS possibly because of its acidic nature. There were significant strong correlations between soil organic carbon and BD (-0.86 *** ), PR (-0.61 * ), MC (0.82 ** ), ATS (-0.62 * ), WSA (0.79 *** ), AWC (0.91 *** ), pH (-0.61 ** ) and TN (0.76 *** ). Grain yields of maize were highest in KS followed by FL and least in CC. The high yields were attributed to improved soil properties in plots of KS compared with both FL and CC. In conclusion, the findings suggested that organic matter had a major influence on soil properties and fertility.

Use of partially-decomposed cattle and chicken manure amended with wood-ash in two South African arable soils with contrasting texture: effect on nutrient uptake, early growth, and dry matter yield of maize

The study was conducted to determine the effects of applying wood-ash to two soils amended with partially-decomposed cattle and chicken manure on the uptake of nutrients, early growth and dry matter yields of maize (Zea mays L.). A clay and silty loam soil was used. Manure was applied to each soil in pots at rates equivalent to 0, 5, and 15 t ha− 1, while ash was applied to each of the manure treatments at rates equivalent to 0 and 2 t ha− 1. In both soils, the addition of chicken manure produced higher plant height, stem diameter, leaves per plant, dry matter yield and tissue concentration of protein, nitrogen (N), and phosphorus (P) than cattle manure. The responses of maize due to manure application were higher in the loam than clay soil. Application of cattle manure produced responses which were less than control in many cases. This was presumed to be due to microbial immobilization of nutrients. Generally, wood-ash improved the responses of maize in the loam but not in the clay soil. The addition of wood-ash to manure in clay soil reduced plant height, dry matter yield, plant tissue protein and phosphorus of maize compared to the control. In both soils, however, the addition of wood-ash improved responses where cattle and not chicken manure was applied. In the latter, the increases in response due to manure rate were higher without ash than with ash. Within the cattle manure rates, wood-ash produced better responses when 5 t ha− 1 manure was applied compared to 15 t ha− 1. It is suggested that higher rates of wood-ash application may have been necessary.

Nutrient availability and maize growth in a soil amended with earthworm casts from a South African indigenous species

The study was undertaken to assess the availability to maize of nutrients from earthworm casts (wormcasts) collected from a grazing paddock in the Eastern Cape province of South Africa. Maize (cv PAN 473) was grown in pots filled with ground wormcasts, non-casted surrounding soil and a mixture of the two media. Fertiliser application increased growth and uptake of nutrients by maize grown on both wormcast and non-casted soil. Maize grown on wormcasts had significantly (p < 0.05) higher plant height, stem diameter, dry weight and showed higher nutrient uptake and lower fertiliser response than that grown on corresponding non-casted surface soil. The uptakes of plant nutrients, growth and dry matter yields were in the order fertiliser>wormcasts>non-casted soil. Mixing worm casts with non-casted soil improved maize growth and nutrient uptake over non-casted soil. It is concluded that wormcasts could be used as a soil amendment for crop production, especially in small-scale production systems.

Using Wood Ash to Ameliorate Acidity and Improve Phosphorus Availability in Soils Amended with Partially Decomposed Cattle or Chicken Manure

The application of partially decomposed animal manure can acidify the soil by nitrification and may cause problems with phosphorus (P) availability. This study investigated the influence of applying wood ash to two soils amended with partially decomposed cattle or chicken manure on pH and P. The treatments consisted of two soils, a clay loam and sandy loam, each amended with partially decomposed chicken or cattle manure applied at 0, 5, or 15 t ha−1, and wood ash was applied to each manure treatment at rates of 0 or 2 t ha−1. The addition of wood ash significantly increased pH, thereby making more P available in soil and maize (Zea mays L.) tissues for both soils after being amended by manure. Both chicken and cattle manure significantly increased all the measured variables compared to the unamended soils. These results suggest that wood ash is an important amendment that could be used to amend partially decomposed manure, thereby not jeopardizing P availability to crops.

Neubauer seedling technique to determine availability of nutrient elements for wheat from selected South African soils

Abstract The quantity of plant nutrient elements removed from soil by wheat (Triticum aestivum) seedlings were compared with the results of soil tests. Four soils were selected to represent the major parent material and climatic factors responsible for the formation of important agricultural soils in the central eastern Cape Province of South Africa. Acid‐washed sand was used as control. Seedlings were grown for 21 days and nutrient element content in both plant material and soil were determined. Soils derived from dolerite rocks had significantly (P<0.05) higher calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and phosphorus (P) than those derived from sedimentary rocks. However, iron (Fe), manganese (Mn), and copper (Cu) were higher in soils derived from sedimentary rocks compared to those from dolerite rocks. The differences are attributed to elemental composition of minerals in the two parent rock materials. Within each rock group, soils derived from sites with higher temperature and low rain...

Decomposition of subtropical fruit tree leaf litter at Nelspruit, South Africa

There is limited information about the decomposition of leaf litter from subtropical fruit trees despite their potential for managing soil fertility. The aim of this study was to quantify the effect of quality on decomposition and nutrient-release patterns from leaf litter of avocado, litchi, and mango trees in South Africa. The litterbag technique was used for investigation. The decomposition results over 2 years indicated significant differences in mass loss among the tree species with low rapid loss for litchi (57.3 percent). The annual decomposition rate constant (k) decreased in the order mango (0.82) > avocado (0.76) > litchi (0.69). The concentrations of phosphorus, potassium, manganese, and polyphenols in all species decreased while nitrogen, sulfur, and calcium concentrations increased with time. The nutrient-release pattern of the leaf litter from the three species varied considerably due to different quality characteristics. This had an influence on litter decomposition and thus its management.