Crop residue burning increased during the COVID-19 lockdown: A case study of rural India

The customary practice of crop residue burning (CRB) is a major policy concern across several developing economies because of the associated increase in air pollution and reduction in soil quality. CRB poses a hazard to public health and sustainable farmland management. We collected original survey data from a panel of 400 wheat farmers on CRB choices during April-May of 2019 and 2020 - with the latter coinciding with India's COVID-19 nationwide lockdown. This timeline of events facilitated a unique identification of changes in CRB that are attributable to the lockdown. Several studies find that lockdowns during 2020 had beneficial effects on the environment owing to reduced economic activity. However, our findings indicate that CRB may have unintentionally increased during the lockdown. A binary variable regression framework analyzes the determinants of CRB choices of farmers over two years. We control for farmers' opinions on various socioeconomic aspects of the pandemic lockdown to examine its effects on their CRB decisions. The lockdown significantly increased the likelihood of CRB by up to 12%. Furthermore, farmers who lost agricultural income and those compelled to sell assets during the lockdown were 22% and 19% more inclined, respectively, to choose CRB. Labor mobility ceased during the lockdown and increased the cost of environmentally friendly farmland management; this increased the likelihood of CRB by 6%. This study contributes to a growing literature on the unintentional consequences of pandemic lockdowns.

Cadmium accumulation in paddy soils affected by geological weathering and mining: Spatial distribution patterns, bioaccumulation prediction, and safe land usage

The abnormal enrichment of cadmium (Cd) in soil caused by rock weathering and mining activities is an issue in southern China. Although the soil Cd content in these regions is extremely high, the bioavailability of Cd in the soils differs significantly. The carbonate area (CBA) and tin-mining area (TIA) in Hezhou City were investigated to determine the primary features of soil Cd mobility in these regions and improve environmental management. Lateral and vertical spatial distributions revealed different accumulation and migration mechanisms of soil Cd in the CBA and TIA. Further analyses revealed that mining activities and geological weathering resulted in different soil geochemical parameters, thus yielding significantly lower levels of Cd in rice grains in the CBA than in the TIA. The random forest (RF) model predicted the bioaccumulation factor (BAF) (R2 = 0.69) better than the support vector machine (SVM) model (R2 = 0.68). Subsequently, a novel land management scheme was proposed based on soil Cd and the prediction of Cd in rice to optimize the spatial resources of agricultural land and ensure the safety of rice for consumption. This study provides a novel approach for land management in Cd-contaminated areas.

Does straw returning affect the root rot disease of crops in soil? A systematic review and meta-analysis

Straw returning is a sustainable way that does not destroy soil ecology in agronomic management. Some studies have found that straw returning may aggravate or reduce soilborne diseases in the past few decades. Despite the increasing number of independent studies investigated the effect of straw returning on root rot of crops, the quantitative analysis regarding the relationship between straw returning and crop root rot is still undefined. In this study, keywords co-occurrence matrix was extracted from 2489 published studies (published from 2000 to 2022, the same below) on controlling soilborne diseases of crops. The methods used for soilborne diseases prevention have shifted from chemical to biological and agricultural control since 2010. As root rot is the soilborne disease with the largest weight in keyword co-occurrence according to statistics, we further collected 531 articles focusing on crop root rot. Notably, the 531 studies are mainly distributed in the United States, Canada, China and other countries in Europe and the south and southeast of Asia, and focus on the root rot of soybean, tomato, wheat and other important grain crops or economic crops. Based on the meta-analysis of 534 measurements in 47 previous studies, we explored how 10 management factors (soil pH/texture, type/size of straw, depth/rate/cumulative amount of application, days after application, beneficial/pathogenic microorganism inoculated before application and annual N-fertilizer input) during straw returning affect root rot onset worldwide. The results showed that straw size and microorganisms inoculated before straw returning are the key factors affecting the incidence of root rot. In combination with actual agricultural production, detailed advice applicable to traditional farming system on the optimization management of straw returning was given. This study emphasized the significance of straw pretreatment and farmland management to reduce soilborne diseases during straw returning.

Effects of soil tillage regime and frequency of cultivation on grassland bird assemblages in Mediterranean drylands

Conservation agriculture (CA) gained recently some visibility in the Mediterranean region. By affecting soil and plant ecology, CA is expected to influence other biological groups, notably farmland birds. This study aims to assess (1) the importance of tillage regime (conventional vs. no-tillage) and frequency of cultivation under these two regimes in determining the richness and abundance of birds in extensive grasslands originated within rotational cropping systems, and (2) how tillage systems contribute to changes in bird richness and abundance, comparatively to other drivers of bird ecology in Mediterranean farmland. We conducted bird censuses (point counts) from 2012 to 2016 in 34-52 fields per year of 15 farms in Évora region (Southern Portugal). Generalized Linear Mixed Models were used to link bird abundance/richness with agricultural descriptors. Both tillage regime and cultivation frequency showed weak effects on Species richness and Total bird abundance. However, a strong variability in the response to tillage descriptors was found between species. For the little bustard and the Iberian grey shrike, a strong interaction with the annual weather regime and opposite trends for the effect of tillage regime were detected. Despite its moderate influence on bird assemblages comparatively to other major drivers of bird richness and abundance (i.e. grazing and annual weather regime), CA could constitute a potential complementary "greening measure" to manage extensive grasslands within rotational cropping systems, particularly in areas where soil erosion is a problem, although some species may not benefit from its implementation.