# Response of Amaranthus Species to Co-Application of Cattle Manure Microdoses, Mineral Fertiliser, and Arbuscular Mycorrhizal Fungi Inoculation on Acidic Soils in South Africa

## TL;DR

This study shows that combining cattle manure, small amounts of fertilizer, and fungi improves Amaranthus growth and nutrient uptake in acidic soils.

## Contribution

The study introduces a novel combination of microdose mineral fertiliser, cattle manure, and AMF inoculation for improving crop performance in acidic soils.

## Key findings

- Cattle manure and AMF inoculation significantly improved Amaranthus growth and yield.
- Nutrient uptake (N, P, K, Ca, Mg, Zn) and residual soil nutrients increased with the treatments.
- Microdose combinations of manure and fertiliser proved effective in resource-limited settings.

## Abstract

Low soil nutrient availability and uptake negatively affect crop productivity in acidic soils. For example, phosphorus (P) availability is reduced by fixation of aluminium (Al) and iron (Fe) hydrous oxides and precipitation with soluble Al and Fe. In addition, soil acidity inhibits root growth, and application of agricultural lime ameliorates these challenges, thereby improving yields. However, resource-limited farmers in the Eastern Cape Province can rarely afford to procure lime and chemical fertilisers, which necessitates alternative approaches to addressing the challenge of low nutrient availability for crops. The present study explores interactions between cattle manure and mineral fertiliser applications coupled with arbuscular mycorrhizal fungi (AMF) inoculation on the agronomic performance of Amaranthus grown in acidic soil. The treatments were 100% cattle manure, 50% cattle manure + 50% NPK fertiliser and lime, 33% cattle manure + 33% NPK and lime + AMF, the recommended rate of mineral fertiliser and lime, AMF, and an absolute control. Cattle manure and mineral fertiliser application, including mixtures of their microdoses, coupled with AMF inoculation, significantly improved the growth and yield of Amaranthus species. Leaf tissue concentrations of N, P, K, Ca, Mg and Zn and their uptake, and selected residual soil properties and nutrients increased significantly following application of the treatments relative to the unfertilised control. The findings of this study imply that application of manure and mixtures of microdoses and mineral fertiliser, together with AMF, improve nutrient uptake and yield of Amaranthus and residual nutrients that benefit subsequent crops.