Soil tilth is a dynamic and multifaceted concept that refers to the suitability of a soil for planting and growing crops. A soil with good tilth is “usually loose, friable and well granulated”; a condition that can also be described as the soil’s having a good “self-mulching” ability. On the other hand soils with poor tilth are usually dense (compacted), with hard, blocky, or massive structural characteristics. Poor soil tilth is generally associated with compaction, induced by wheel traffic, animal trampling, and/or to natural soil consolidation (i.e., so-called hard-setting behavior). The soil-tilth concept dates back to the early days of arable farming and has been addressed in soil-science literature since the 1920s. Soil tilth is generally associated with soil’s physical properties and processes rather than the more holistic concepts of soil quality and soil health. Improved soil tilth has been associated with deep and intensive tillage, as those practices were traditionally considered the primary method for creating a suitable soil condition for plant growth. Therefore, for millennia there has been a strong focus both in practice and in research on developing tillage tools that create suitable growing conditions for different crops, soil types, and climatic conditions. Deep and intensive tillage may be appropriate for producing a good, short-term tilth, but may also lead to severe long-term degradation of the soil structure. The failure of methods relying on physical manipulation as means of sustaining good tilth has increased the recognition given to the important role that soil biota have in soil-structure formation and stabilization. Soil biology has only received substantial attention in soil science during the last few decades. One result of this is that this knowledge is now being used to optimize soil management through strategies such as more diverse rotations, cover crops, and crop-residue management, with these being applied either as single management components or more preferably as part of an integrated system (i.e., either conservation agriculture or organic farming).Traditionally, farmers have evaluated soil tilth qualitatively in the field. However, a number of quantitative or semi-quantitative procedures for assessing soil tilth has been developed over the last 80 years. These procedures vary from simply determining soil cloddiness to more detailed evaluations whereby soil’s physical properties (e.g., porosity, strength, and aggregate characteristics) are combined with its consistency and organic-matter measurements in soil-tilth indices. Semi-quantitative visual soil-evaluation methods have also been developed for field evaluation of soil tilth, and are now used in many countries worldwide.
Lars J. Munkholm, Mansonia Pulido-Moncada, and Peter Bilson Obour
Agriculture is practiced on 38% of the landmass on Earth, and having replaced natural ecosystems, it is the largest terrestrial biome on Earth. Agricultural biomes are typically focused on annual crops that are produced as a succession of genetically uniform monocultures. Compared to the ecosystems they replaced, agroecosystems provide fewer ecosystem functions and contain much less biodiversity. The large-scale conversion from natural lands to agriculture occurred centuries ago in the Old World (Africa, China, Europe, and India), but in many areas during the latter 20th and early 21st centuries, especially tropical areas with rich biodiversity, agriculture is an emerging industry. Here, displacement of natural ecosystems is also a late 20th-century occurrence, and much of it is ongoing. Regardless of where or when agriculture was established, biodiversity declined and ecosystem services were eroded. Agricultural practices are the second largest contributor to biodiversity loss, due to the loss of habitat, competition for resources, and pesticide use. Most (~96%) of the land used to produce crops is farmed using conventional methods, while smaller percentages are under organic production (~2%) or are producing biotech crops (~4%). Regardless of how agriculture is practiced, it exacts a toll on biodiversity and ecosystem services. While organic agriculture embraces many ecological principals in producing food, it fails to recognize the value of biotechnology as a tool to reduce the environmental impact of agriculture. Herbicide- and/or insect-resistant crops are the most widely planted biotech crops worldwide. Biotech crops in general, but especially insect-resistant crops, reduce pesticide use and increase biodiversity. The widespread adoption of glyphosate-resistant crops increased the use of this herbicide, and resistance evolved in weeds. On the other hand, glyphosate has less environmental impacts than other herbicides. Because of the limited scale of biotech production, it will not have large impacts on mitigating the effects of agriculture on biodiversity and ecosystem services. To have any hope of reducing the environmental impact of agriculture, agro-ecology principals and biotechnology will need to be incorporated. Monetizing biodiversity and ecosystem services through incorporation into commodity prices will incentivize producers to be part of the biodiversity solution. A multi-level biodiversity certification is proposed that is a composite score of the biodiversity and ecosystem services of an individual farm and the growing region were the food is produced. Such a system would add value to the products from farms and ranches proportionate to the level by which their farm and region provides biodiversity and ecosystem services as the natural ecosystem it replaced.
Soils, the earth’s skin, are at the intersection of the lithosphere, hydrosphere, atmosphere, and biosphere. The persistence of life on our planet depends on the maintenance of soils as they constitute the biological engines of earth. Human population has increased exponentially in recent decades, along with the demand for food, materials, and energy, which have caused a shift from low-yield and subsistence agriculture to a more productive, high-cost, and intensive agriculture. However, soils are very fragile ecosystems and require centuries for their development, thus within the human timescale they are not renewable resources. Modern and intensive agriculture implies serious concern about the conservation of soil as living organism, i.e., of its capacity to perform the vast number of biochemical processes needed to complete the biogeochemical cycles of plant nutrients, such as nitrogen and phosphorus, crucial for crop primary production. Most practices related to intensive agriculture determine a deterioration even in the short-middle term of their physical, chemical, and biological properties, which all together contribute to soil quality, along with an overexploitation of soils as living organisms. Recent trends are turning toward styles of agriculture management that are more sustainable or conservative for soil quality. Usually, use of soils for agricultural purposes deflect them at various degrees from the “natural” soil development processes (pedogenesis), and this shift may be assumed as a divergence from soil sustainability principles. For decades, the misuse of land due to intensive crop management has deteriorated soil health and quality. A huge plethora of microorganisms inhabits soils, thus acting as “the biological engine of the earth”; indeed, this microbiota serves the soil ecosystem, performing several fundamental functions. Therefore, management practices might be planned looking at the safeguard of soil microbial diversity and resilience. In addition, each unexpected alteration in numberless soil biochemical processes, being regulated by microbial communities, may represent an early and sensible signal of soil homeostasis weakening and, consequently, warn about soil conservation. Within the vast number of soil biochemical processes and connected features (bioindicators) virtually effective to measure the sustainable soil exploitation, those related to the mineralization or immobilization of the main nutrients (C and N), including enzyme activity (functioning) and composition (diversity) of microbial communities, exert a fundamental role because of their involvement in soil metabolism. Comparing the influence of many cropping factors (tillage, mulching and cover crops, rotations, mineral and organic fertilization) under both intensive and sustainable managements on soil microbial diversity and functioning, through both chemical and biological soil quality indicators, makes it possible to identify the most hazardous diversions from soil sustainability principles.