Ingrid Martínez ^1* Claudia Di Bene ² Patricio Sandaña ^3*

• ¹ Instituto de Investigaciones Agropecuarias, INIA Remehue, Osorno, Chile
• ² Council for Agricultural Research and Agricultural Economy Analysis | CREA, Rome, Lazio, Italy
• ³ Universidad Austral de Chile. Instituto de Producción y Sanidad Vegetal., Valdivia, Chile

Although the increased use of synthetic fertilizers has improved soil nutrient availability and crop productivity, it has also resulted in an increase in soil acidification which can be harmful to the long-term sustainability of agroecosystems. This is particularly the case for the 40% of arable lands worldwide that are naturally acid (Kamprath and Smyth, 2005). Soil pH regulates the capacity of soils to store and supply nutrients and thus contributes substantially to controlling productivity. Indeed, small changes in water balance cause a steep transition from alkaline to acid soils across a natural climate gradient, showing that climate controls many aspects of soil chemistry and thus affecting soil acidity (Owusu et al., 2023;Slessarev et al., 2016). This Research Topic, Strategies to reduce fertilizers: How to maintain crop productivity and profitability in agricultural acidic soils aimed to provide a discussion update on new strategies needed to reduce fertilizer use that will help us achieve a more sustainable agriculture by promoting crops and varieties that are more resource-efficient (i.e. nutrients) and more able to adapt to specific soil conditions such as low fertility, low pH and associated aluminum and manganese toxicity. This will ensure the continued cultivation of agricultural lands, minimize fertilizer inputs, and reduce transport costs -especially in remote areaspromoting organic local amendments and strengthening resource-poor low-income family farming. Presents two review papers, including a worldwide meta-analysis of fifty-decades, as well as, the study of farmer's perception on the environmental impact of chemical fertilizers, and has research papers that span studies from Chile to China. Here, were summarized some of the highlights derived from the six articles published in this research topic.The study of Moggia et al. demonstrated that the methodology used to predict early nutritional imbalances in apple commercial orchards planted in acid soils, is essential to understand the factors that determine the Bitter pit (BP), a post-harvest apple disorder linked to calcium deficiency and mineral imbalances like potassium. It is challenging to predict BP, due to variability in mineral levels within and across fruits. X-ray fluorescence (XRF) spectrometry enables non-destructive analysis of mineral composition in individual apples, aiding prediction. This study tested multivariate modeling with XRF data to enhance BP prediction. Using a balanced dataset of BP-affected and healthy apples, four additional elements (Cl, Si, P, S) were identified as predictors alongside K and Ca. Multivariate models outperformed univariate methods, achieving sensitivity and specificity of 0.76-0.92, highlighting XRF's potential for precise BP prediction. This BP prediction could be examined periodically during the season, which is of great importance to allow better effectiveness of foliar calcium applications. Dai et al. explored the best fertilization management strategy to obtain high grain yields and N use efficiency in a 41-year long-term experiment in China under a subhumid climate. They demonstrated that the NPK application plus manure addition in a soybean-maize-maize rotation increasing crop yield and decreasing fertilizer N losses and thus environmental risks.Liming acidic soils is generally promoted as an effective management practice to increase soil pH, base cation concentrations and ameliorate toxicity caused by aluminum and manganese. Enesi et al. reviewed how liming can increase pH and crop yields under different agricultural practices. The meta-analysis showed that the liming effect on crop yield was greater in no tillage systems than in conventional tillage. Application of organic fertilizer and liming increase yields more than liming and inorganic fertilizers. Xu et al. investigated yield and nutrient composition of five forage crops and their effects on soil characteristics in South of China. They could design an alternative nutrient management strategy for rice growers. While Vicia villosa improved soil characteristics, Lolium multiflorum pursue higher forage yields. These results provide useful information on how to integrate forage into farming systems. Additionally, they found that crop species had a significant effect on microbial community of soils, which may also affect the nutritional value of crops.It has been a challenge to reduce the excessive amounts of fertilizer for the production of high-yield crop yield. Although many studies have shown that fertilizer inputs in northern China are excessive, Zou et al. investigated an optimal rate of fertilizer application. They found that a reduced fertilizer application by 10-20% is safe and feasible to maintain the production of maize crops in the region. Sande et al. discussed strategies to mitigate the environmental impact of chemical fertilizers. Their systematic review explored synergies of vermicompost, fertilizers and bio-enriched rock phosphate in nutrient management. They also discussed the importance of farmer education in fostering the adoption of sustainable practices.Nowadays, as the fertilizer prices increase, is a challenging to maintain crop productivity and its profitability. This Research Topic will offer valuable insights of strategies which provide recommendations to reduce fertilizer inputs and sustainable improvement of soil health.