Improvement in dryland crop performance and soil properties with multiple annual applications of lignite-derived humic amendment

Abstract

Humic amendment (HA) is increasingly being evaluated and utilized to improve soil health and crop productivity in intensely farmed arid and semi-arid regions. However, the scientific comparison of field-scale use of single vs. repeated application of HA has not been reported. A field study was conducted to quantify the effect of different numbers of annual HA applications on (i) oat crop performance indicators, and (ii) the changes in soil health metrics in a dryland farming ecosystem. We found that multiple years of annual HA application improved crop growth, and increased grain protein yield (up to 60%), grain yield (21%), water use efficiency (22%), partial factor productivity of nitrogen (21%) and economic benefit (34%) over that for the control (no HA) during both a wetter and a drier growing season. The greater input of crop residue associated with higher yields led to an increase of soil organic carbon and water storage at both 0–20 and 20–60 cm soil layers, and a reduction in soil electrical conductivity, pH and bulk density with increasing years of HA application. There was an overall improvement in soil micro-environmental conditions. These in turn promoted an increased activity of the soil enzymes urease (up to 89%), invertase and catalase and soil nutrient turnover and availability (e.g. up to 58% higher plant available nitrogen). Our results show for the first time that repeated annual HA application of at least 2 years would be a cost-effective strategy to combat land degradation and nurture sustainable crop production in dryland agriculture under widely varying weather scenarios expected with climate change.