Not AvailableHighly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high
rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to
prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances
for its cultivation. Providing proper nutrient management is important for balancing the nutrient
removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of
inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of
organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment
consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM+biofertiliser consortia; FYM, rock phosphate
and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ
composting using recyclable cashew biomass and weeds+green manuring; vermicomposting of recyclable
cashew biomass; FYM+organic cakes+recyclable cashew biomass+biofertiliser consortia; recommended
dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser+FYM; and
control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples
were fractionated into three aggregate sizes, i.e.,>2mm (large macroaggregates), 0.25–2mm (small macroaggregates),
0.053 to 0.25mm (microaggregates) and<0.053mm (silt+clay size fraction) using wet sieving.
The results indicated that the organic sources of nutrient application increased the proportion of large and small
macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly
higher silt+clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates
(47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the
application of organic sources of nutrients. Aggregates in the silt+clay size faction and microaggregates recorded
significantly higher carbon compared to small and large macroaggregates. Compared to control, the
application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt+clay
size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large
macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered
tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial
carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.Not Availabl