Impact of agricultural inputs on soil organisms—a review

TLDR

Agricultural inputs such as mineral fertilisers, organic amendments, microbial inoculants, and pesticides are applied to maximise productivity, yet their side effects on soil organisms are often overlooked and require quality control to prevent toxic accumulation. Organic amendments supply both direct carbon to soil organisms and indirect carbon via enhanced plant growth and residue return. Mineral fertilisers mainly boost soil biological activity indirectly, while N fertilisation can acidify soils and harm organisms; microbial inoculants have minor transient effects, herbicides rarely affect soil biota, but insecticides and fungicides—especially copper—often exert negative impacts, underscoring the need for careful regulation.

Abstract

External agricultural inputs such as mineral fertilisers, organic amendments, microbial inoculants, and pesticides are applied with the ultimate goal of maximising productivity and economic returns, while side effects on soil organisms are often neglected. We have summarised the current understanding of how agricultural inputs affect the amounts, activity, and diversity of soil organisms. Mineral fertilisers have limited direct effects, but their application can enhance soil biological activity via increases in system productivity, crop residue return, and soil organic matter. Another important indirect effect especially of N fertilisation is soil acidification, with considerable negative effects on soil organisms. Organic amendments such as manure, compost, biosolids, and humic substances provide a direct source of C for soil organisms as well as an indirect C source via increased plant growth and plant residue returns. Non-target effects of microbial inoculants appear to be small and transient. Among the pesticides, few significant effects of herbicides on soil organisms have been documented, whereas negative effects of insecticides and fungicides are more common. Copper fungicides are among the most toxic and most persistent fungicides, and their application warrants strict regulation. Quality control of organic waste products such as municipal composts and biosolids is likewise mandatory to avoid accumulation of elements that are toxic to soil organisms.