There is a paucity of information on nitrogen (N) and phosphorus (P) mineralization in humic soils, which are highly weathered and have high carbon (C) (>1.8%). This study was to determine effects of liming on N and P mineralization in humic soils. Lime was applied to reduce acid saturation to 20% of the 0–10 and 10–20 cm depths of soils from Eston and Eshowe. Soils were incubated at field capacity moisture and 25 °C temperature, with destructive sampling after 0, 7, 14, 21, 28, 56, 84 and 112 days. Samples were analysed for pH, ammonium- and nitrate-N and extractable P. Phosphorus pools and soil microbial biomass C and N (SMBC and N) were analysed after 112 days only. Soil pH increased up to day 7 and decreased thereafter in Eston soil but decreased throughout the incubation in Eshowe soil. Ammonium- and nitrate-N increased with lime rate, with ammonium-N peaking after 7 and 14 days for Eston and Eshowe soils, respectively. The 0–10 cm depth had higher ammonium-N than 10–20 cm for both soils. Nitrate-N increased with corresponding decrease in ammonium-N. Extractable P decreased till day 21 and increased thereafter in Eston soil, with slight changes in Eshowe. Higher lime rate decreased Al-P, Fe-P and CBD-P and increased soluble-P, Ca-P, and SMB-C and N for both soils. The findings imply that liming humic soils increase nitrate-N and, to a lesser extent, extractable P, possibly improving productivity and exposing N to leaching.

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Understanding farmer perceptions of soil fertility is necessary for the development of appropriate assessment methods for sustainable agro‐ecosystems. This study investigated farmer perceptions of soil fertility and management in four villages of eastern South Africa. A questionnaire was administered to 50 farmers from each village to obtain a general overview of local soil knowledge as well as soil fertility perceptions and assessment. Ten farmers were then chosen from each village for in‐field walks and to gather in‐depth knowledge of local soil fertility concepts, soil‐crop associations and soil management. During in‐field walks, farmers were asked to identify fertile, moderately fertile and low soil fertility plots in their fields from which topsoil samples were taken for laboratory fertility analysis. Local soil fertility descriptors included crop performance and yield, soil texture, stoniness and consistence. Using these descriptors, farmers have developed specific soil use and management practices. There was generally poor agreement between farmer qualitative assessment and measured chemical fertility parameters. However, the study revealed that the generally ignored local qualitative soil knowledge of farmers could be linked to crop performance and potentially supports laboratory soil analysis in terms of its implication for smallholder agriculture in remote areas. The descriptors identified and overall assessment used by farmers in this study reflected considerable soil knowledge employed in daily decision‐making. Action learning and research that links local soil fertility descriptors to soil acidity and specific soil nutrient levels is thus recommended for effective identification of yield‐limiting factors for sustainable crop production in low‐input agriculture.

Long-term N addition and liming did not affect bulk SOC content and stocks but lead to redistribution of C into water stable aggregates. Long-term N fertilization caused soil acidification and reduced mean weight diameter. Long-term N fertilization increased micro-aggregates and SOC stored in them. Long-term liming did not affect WSA, and C stored in them. Liming improved aggregation and increased C associated with large macro aggregates when co-applied with N fertilizers.

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Ethnopedological studies focus on agricultural soils resulting in undervaluation of non-agricultural soil materials during land classifi cation. In this study, ethnographic and ethnopedologic methods were used to obtain local knowledge and gain in-depth understanding of non-agricultural soils, their mineralogical and elemental composition relating to application in geophagy, healing and cosmetic purposes in two villages in KwaZulu-Natal, South Africa. In each village a questionnaire was administered to fi fty randomly selected individuals from which ten knowledgeable volunteers (including eight geophagists from two villages) provided details on the selection criteria, the desired properties and why the soils performed the claimed role. Users based their selection on macromorphological features (e.g. colour, texture and location within the soil) and indigenous knowledge. Geophagic materials were mainly sourced from C horizons. They were mostly fi ne-grained with mica, kaolinite and quartz, and elements such as copper (Cu), zinc (Zn), cobalt (Co) and lead (Pb). Natural pigments, such as iron oxides in highly weathered soils, were recognised as sunscreen materials. Although the mechanisms were not understood by users, laboratory analyses showed that the mineralogical and chemical properties of the soil materials played a crucial role. The sunscreen and healing capabilities of these soils were related to high contents of titanium (TiO 2 ) and iron (Fe 2 O 3 ) and the presence of kaolinite. Further appraisal of these soil materials is necessary for their conservation and inclusion in land classifi cation.

Large amount of wastes are burnt or left to decompose on site or at landfills where they cause air pollution and nutrient leaching to groundwater. Waste management strategies that return these food wastes to agricultural soils recover the carbon and nutrients that would otherwise have been lost, enrich soils and improve crop productivity. This study characterised biochar produced by pyrolysis of potato peels (PP), cull potato (CP) and pine bark (PB) at 350 and 650°C. The biochar types were analysed for pH, phosphorus (P) and other elemental composition. Proximate analysis was done following ASTM standard 1762–84, while surface functional groups and external morphology characteristics were determined using FTIR and SEM; respectively. Pine bark biochar had higher yield and fixed carbon (FC), and lower ash content and volatile matter than biochar types from potato wastes. The liming potential of CP 650°C is greater than that of PB biochars. Biochar types from potato waste had more functional groups even at high pyrolysis temperature relative to pine bark. Potato waste biochars showed an increase in pH, calcium carbonate equivalent (CCE), K and P content with increasing pyrolysis temperature. These findings imply that biochar from potato waste may be valuable for soil C storage, remediating acidity and increasing availability of nutrients especially K and P in acidic soils.