Liming effect on soil chemical and biological properties, pests and diseases, and crop yields in robusta coffee and black pepper in Vietnam

Abstract

Context: Vietnam is the global leading producer of robusta coffee and black pepper. However, expanding coffee and pepper cultivation and intensive farming practices have led to soil acidification and increased pest and pathogen pressures. Agricultural liming applications could sustainably alleviate acidification, modify soil physicochemical parameters, restore microbial ecosystems, and suppress soil pathogens. Aims: To address this issue, field trials were conducted in Gia Lai province in acidic soil within coffee and pepper plantations. Methods: Two treatments were applied: 2.5 t ha-1 of dolomite lime and a no-lime control. The trials assessed soil chemical and biological properties, soilborne pests and diseases, and crop yield. Key results: The results indicated no significant yield differences between the lime-treated and control crops. However, application of lime effectively raised soil pH by around 0.5 units for coffee and 0.4 units for pepper, compared to the free-lime treatment. In contrast, soil pH in the control plots decreased by 0.3 units (6.8%) for coffee and 0.2 units (3.8%) for pepper plantations compared to the pre-application values. In coffee plantations, lime application led to significant enhancements in organic matter and exchangeable K+, Ca2+, and Mg2+ by 17.4%, 26.1%, 103.6%, and 243.7%, respectively. It also decreased exchangeable Fe3+ and Al3+ by 9.7% and 30.3%, respectively, compared to the control. Additionally, lime application significantly improved root mycorrhization by arbuscular mycorrhizal fungi. In pepper farms, liming considerably improved available NH+4 and NO-3 and exchangeable Ca2+ and Mg2+ by 7.5%, 9.8%, 35.1%, and 132.8%, respectively. Exchangeable Fe3+ and Al3+ decreased by 29.8% and 29.0%, respectively. However, for both commodities, no positive effects of liming were observed for populations of pathogenic fungi, oomycetes, and nematodes. Conclusions: Lime had positive effects on soil chemical properties and colonisation by arbuscular mycorrhizal fungi but did not significantly affect soilborne pathogens and crop yield. Implications: Sustainable soil acidity mitigation and improvement of soil fertility could be undertaken by annual lime application. Alternative practices, including biological and ecological approaches, should be explored in conjunction with the use of lime.