Global warming is induced by several factors, notably by the emission of greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O) by some agricultural practices. Agronomists Vermue et al. measured the nitrous oxide emissions of various weed management options. They found the highest emissions, of 5226 g per hectare, in the no tillage system, versus 177 g for intensive tillage. Most N2O emissions occurred in spring.
Conservation tillage is any method of soil cultivation that leaves the previous year’s crop residue, such as corn stalks or wheat stubble, on fields before and after planting the next crop, to reduce soil erosion and runoff. Presently, little is known about the effect of conservation tillage on soil microbes. Wang et al. show that conservation tillage increases the amount of bacteria species that are beneficial to crop production.
Industrial agriculture has degraded soils worldwide, leading to loss of fertility and poisoning food and water. There is therefore a need for sustainable soil management, that is keeping both soil qualities and crop yield. Stavi et al. reviewed ecosystem services provided by soils and compared the various soil management options, e.g. conventional, conservation, and integrated management. They found that moderate-intensity systems are the best to keep both soil qualities and crop yield. Conservation agriculture gave the best ecosystem services, whereas integrated agriculture showed the best crop yield scores.
Most current agricultural practices are not sustainable. For instance the discharge of livestock manure is polluting waters. A solution to avoid manure disposal is to compost manure with maize and worms, so-called vermicomposting. Scientists Guo et al. studied the economical benefits of vermicomposting cattle manure with maize. They found that vermicomposting increases agricultural benefits by 304% compared to classical composting.
Soil contains a huge number of very diverse living organisms such as worms, fungi and bacteria. Many of these organisms work for the benefit of agriculture by recycling organic water, cleaning pollution and transforming atmospheric dinitrogen gas into free fertilisers. So far soil organisms are underutilised because many organisms are not even identified, and their beneficial expertise is often unknown. Microbiologists Degrune et. al set up a new method that allows to distiguish microbial communities in soils cultivated with different cropping practices.
Organic producers in the United States would like to no-till, but are concerned about managing weeds without tillage. Agronomist Randy Anderson shows that weeds can be controlled without tillage in experiments in the Great Plains of the USA. One favorable tactic is to include a 3-year interval of red clover in the rotation. Red cover suppresses both annual and perennial weeds, and it can be converted to cropland by fall mowing in the 3rd year (Photo). The complex rotation increases the impact of no-till on weed seed decay in soil and provide numerous opportunities for cover crops to replace tillage for controlling weeds. These benefits suppress weed growth and interference such that organic producers may be able to continuously no-till in their farming systems.
Industrial monoculture is often leading to the depletion of soil life and quality as a result of intensive tilling. New advanced techniques such as no-till and strip-till farming allow to restore soil fertility in the long run. No-till farming increases soil water, soil organic matter and decreases soil erosion. In strip till the farmer tills only the portion of the soil that will contain the seed row. Islam et al. studied no-till strip farming of maize-soybeans rotations. They observed a 75% increase of maize yield, amounting to 18.4 tons per hectare, after 5 year of cultivation.
The area of agricultural land on saline soils is increasing as a result of climate change and more frequent droughts. Since salt at high concentration is toxic to most plants, cultivation on such soils is becoming more and more difficult and induces yield losses. There is therefore a need for strategies to grow plants on saline soils. Farooq et al. review the mechanisms of maize resistance under salt stress. They propose solutions such as the use of arbuscular mycorrhizal fungi to improve plant nutrition.
Industrial agriculture is known to decrease biodiversity and degrade soil structure. Agronomists Sánchez-Moreno et al. studied the impact of herbicides and soil management on nematodes – soil worms – and other soil life in Mediterranean areas. They found that soil life diversity is decreased by herbicides.
Most plastic products contain phthalic acid esters that end up polluting water and soil after plastic degradation. Indeed, phthalic acid esters are endocrine disruptors. China is one of the largest consumers of phthalic acid esters. He et al. review the contamination of soils by phthalic acid esters. Findings show that the levels of phthalic acid esters in chinese soils are higher than recommended limits, thus contaminating vegetables. The main sources of phthalic acid esters in soils are plastic agricultural films, municipal biosolids, agricultural chemicals and wastewater irrigation.
