Agricultural and Biological Sciences · Soil Science
A 20-year comparison in California’s Central Valley found that reduced tillage with cover crops produced more stable soil aggregates, greater water retention and different forms of carbon protection than standard tillage without cover crops. The conservation system also retained room for additional carbon storage, although the study measured potential rather than future gains.
A field experiment in India found that maize supplied with 75% mineral NPK, vermicompost and Azotobacter–Bacillus inoculation produced 40.8 quintals of grain per hectare. The treatment also improved measures of soil microbial activity compared with sole 100% NPK, but the results need testing across more seasons and locations.
A field study found that urea delivered in clay-and-biopolymer composites with phosphorus- and zinc-releasing bacteria improved nutrient levels in wheat and maize. The treatments also reduced cumulative nitrous oxide emissions by up to 29% compared with a full conventional urea application.
Nitrogen fertilizer increased nitrous oxide emissions from Chinese croplands by an estimated 237.8% compared with unfertilized controls in a meta-analysis of 462 field observations. The size of the increase varied among regions and was also linked to fertilizer rates, fertilizer type, cropping systems, weather and soil texture.
Agricultural lime is generally counted as a source of carbon dioxide, but a study of the Mississippi River Basin finds that it acted as a net carbon sink over the past century. River records indicate that about 90% of the lime’s ideal carbon-removal potential was realized, equivalent to approximately 0.44 gigatonnes of carbon dioxide.
Maize varieties responded differently to beneficial soil fungi, but mixtures of varieties produced more biomass and captured more phosphorus than single-variety plantings. The results suggest that combining locally adapted maize mixtures with these fungi could support more sustainable production in sub-Saharan agroecological systems.
On a steep hillside in northwestern Benin, circular and rectangular honeycomb-shaped stone arrangements reduced runoff and soil loss compared with ordinary contour stone rows. When paired with reduced fertilizer doses, the circular layout was associated with 87.42% more sorghum grain yield than the standard stone-row treatment.
A meta-analysis of 79 articles found that winter oilseed rape, also called winter canola, grown between main crops was associated with higher summer-crop yields, improved soil indicators and greater soil-carbon storage. Methane emissions fell, but nitrous oxide emissions rose; overall emissions were similar to fallow systems and lower than wheat-based rotations.
Long-term trials in Bihar, India, found that manure and crop residues improved soil properties and raised rice and wheat yields. Reduced tillage mainly benefited physical soil conditions, but zero-tillage results varied by site and could lower yields when residues were not added.
Mediterranean dryland crops face cycles of drought and then sudden rain. In a year-long field experiment, researchers found that the biggest bursts of nitrogen pollution in the form of nitrous oxide and nitric oxide followed rewetting, especially when plants had been stressed by drought. Soil texture changed how much inorganic nitrogen built up, but it did not lead to proportionally larger gas spikes.
