Beyond erosion control, the benefits of no-till in agro-ecosystems.
Modern agriculture is under pressure to modify its traditional techniques from ecologists, activists, and consumers. Many have turned to organic farming to reduce seasonal costs, build soil and sell a high profit product. Just a few changes are required while retaining the mechanical systems in place. The question is if you can change conventional production practices to organic practices, and spray, hybridized, and ship it 1500 miles or thousands, is it still organic? With hoop house production, is it organic when its surrounded by plastic, fed by plastic tubes and heated by propane? Even the title of our class, Organic Vegetable Production focuses all the attention on the vegetable. The result is the organic vegetable. If perhaps it were called Organic Production of Vegetables, the focus would be on the practices as being organic. But we focus on the vegetable product in the end and like many thing externalize the costs to produce the desired effect. Currently the popular methods seem to be in segregated systems that reduce field soil to an inert growing medium wholly dependent of chemical additives and fabricated materials. If we could manage the connected ecological soil resource with inclusive systems, rather than excluding the natural organisms, we might gain long-term benefits and highly productive fields. Organic production means the production methods and materials are ecologically founded, resourced and cycled. To that end the introduction and support of macro fauna and beneficial organisms on all levels enhances the fertility and organic material in soil. The exclusion of natural micro-"livestock" from our production beds causes additional energy and stress on the plants and grower. In this paper I will address the benefits of using mega fauna and fungi in growing systems as a truly organic solution to increased soil health and thus fertility. At the Moses conference, Jeff Lowenfels, Using Mycorrhizae for Crop Production, spoke of fungi and mycorrhizae. He connected the soil web beneath the ground to the plants needs and pretty much stopped at that as if the mycorrhizae needed no other services. Fungi along with most all under ground life are threatened by cultivation in fields. I thought it would be good to visit that topic and the underground economy we take for granted. Mycorrhizae cytoplasm break down the carbon chains for bacteria, bacteria create soil tilth and occupy the gut of many mega fauna organisms metabolizing pathogens. The food web is complex and redundant in a healthy soil. Mechanical and chemical disruption of the food web reduces the soil health.
Agriculture researchers and growers alike have ignored or forgotten the underground ecology (Jackson 1995). It is an area misunderstood and moreover unstudied (Andre 1994). With the exception of Earth worms and nitrogen fixing bacteria whose life histories have been documented. Organisms in mutualistic, predatory and successive relationships do many important ecological functions in the soil.
The cultivation of soils and frequent disturbance to established soil organism communities disrupts the cycle that would naturally create fertility in the soil. The soil structure is damaged regularly in garden as rototillers seasonally “prepare” the soil for winter or spring planting. Doing so destroys the Glomalyn connections from fungi and disrupts established nutrient transfer systems needed by plant roots (Lowenfells, 2011). It also segregates the organisms in extreme variations in soil until once again it is broken into even smaller section before planting and although organic matter will decompose faster it can take sixty days for the fungi to reconnect through the fractured horizon.
o Bacteria, produce polysaccharide adhesives connecting soil clumps, biocontrol agents (Ryder et al, 1990).
o Fungi, extend their hyphe long distances through soil particles creating stability. 30-70% of carbon in soil is cycled through Fungi. Break down Phosphorus (Lowenfells, 2011).
o Algae, polymer production and cohesion of soil particles (Hu C., Liu Y., Paulsen B.S., Petersen D., Klaveness D, (2003).
§ Promote carbon in shoot growth and disease suppression through predation of pathogenic nematodes, bacteria, and fungi (Zwart 1977).
o Mites, numerous in sandy soils, prairie and grass, less in clay and root crops systems. (Benckiser,1997).
It should be noted that worm species in the fungal habitat could become invasive and modify the soil ecology indefinitely (Woodrill Nature Center, 2009).
The roles of each group of organisms are varied by size and phrenology. The soil food web system contains producers, consumers and ditrivores. Many of the species are omnivores taking advantage of resources available and in that sense are redundant sources for similar plant nutrients (Neher 1999). At the same time each is vulnerable to cultivation of the soil causing some to flourish from perturbation and others to diminish, throwing off equilibrium of ecological services that may have been provided otherwise.
Promoting Plant Growth
Blue Gramma Grass has been shown to have high productivity with the addition of microbial grazers, to existing primary decomposers (Ingham et al, 1985; Neher, 1999). Blue Gramma also extracted more nitrogen with the assistance of amoebae in the soil (Zwart et al, 1994).
Plants growth increased with protozoa and nematodes in the soil (Heher, 1999; Verhoef and Brussaard, 1990; Griffiths, 1994; Alphei et al., 1996).
A more complex food web increases nutrient availability through redundant access of the plants. According to Hunt et al, 1995, woodland seedlings, birch (Betula pendula) and Scots pine (pinus sylvesttris) increased shoot production 1.5 and 1.7 times respectively. In this research the two compared soil communities contained bacterial and fungal feeding nematodes, but the second also had omnivores, springtails, and orbitad mites. The extended food chain increased nutrient availability to the plants.
The soil food web is the habitat for the organisms. It is a complete cycle from plants adding organic matter and sugars to the soil to organisms consuming the materials, each others and releasing the organic nutrients as mineralized and available to the plant root uptake. Plant roots are the externalized gut of the plant (Janzen 1995, Neher 1999) and contributes sugars and nutrients to the soil. The exudates of the roots increase microbial activity. The microbes are consumed by mega and meso fauna, their inner gut collecting, metabolizing and mineralizing nutrients, which are cycled back to the soil.
Increased soil temperature raises the activity of the microbes and the access of plants to nutrients (Lavelle, et al, 1995). This evidence of increased mutualistic responses shows the connection between the organisms in the soil and the plant appearing above. The cascading effect of increased organic life and material in the soil would support decreased disturbances to the soil and increased resources for the soil food web. This would also increase the diversity of organisms and reduce pathogenic disease.
Soil acts as a growing medium, buffer to environmental changes, and storehouse of nutrients for plants. The plants and organic material of the higher soil horizons provide the spaces for organism habitat. The organisms in the soil depend on the producers to supply consumable organic material. Micro fauna occupy the soil pores while larger ones travel in the spaces and fractures around the more dense areas. As each travels and eats through the soil spaces, their by products enrich the soil and create the soil tilth that holds it from erosion while increasing the water holding capacity and reducing nutrient loss. Allowing the soil to build structure and porosity increases the ability for it to absorb and hold precipitation, slow the loss of water and reduce the leaching of nutrients to subsoil horizons. The organisms regulate the decomposition at a pace conducive to need and condition the soil food web (Beare, 1997). Increased diversity inhibits pathogenic transmission allowing the soil food web to deter invasive organisms.
There are three access routes to nutrients in and out of the soil. By roots, bacteria, and fungi. (Moore, et al, 1988). Roots transfer to the herbivorous consumers such as fungi, bacteria and nematodes. These are also consumed concentrating and disbursing materials to broader areas. Bacterial ecology of soil dominates in agricultural land and prairie. Fungal ecology is dominant in forests ad woodlands. Buy limiting cultivation and using no-till techniques, the organism ecology in each area is allowed to establish the natural processes and develop natural storehouse of resources in the soil. Adding mineral fertilizers to the soil can eliminate omnivorous and predacious nematodes and mycorrhizae disrupting the soil food web. Cultivating stresses the larger fauna and dries the porous areas where microbes and bacteria reside.
Microfauna and mesofauna are too small to restructure soil and are greatly limited by isolating disturbances like plowing. Worms naturally shape the soil cavities and structure moving bacteria, organic material and moisture, working in concert with the smaller creatures.
Trophic diversity, at all levels is the expansion of producers and consumers of varied species. When a field is cultivated, habitat is disturbed and fitness pressure reduces the diversity to those organisms that can withstand the extreme changes, non-ecological factor. (Hendrix et al, 1986). Pockets of habitat are disbursed. Undisturbed habitat allows for natural ecosystem processes to continue and reduced stress allows organisms to increase diversity, numbers, and sequestered resources. Improved ecosystem function extends the food chain to diverse herd of soil organisms creating increased functions for fertility. Developing this broader and deeper cache of soil organisms in the growing areas enhances the five ecological functions identified by Larson and Pierce, (1995).
To adapt current practices to more ecological founded benefits, growers might incorporate new techniques.
Tillage is a constant compromise in organic and conventional fields. Soil is highly sensitive to tillage and decomposition can be enhanced or inhibited. Beare, (1977) found conventional tillage to accelerate decomposition by 1.4 to 1.9 times. As noted previously, Fungi are more active in no-till with accumulating surface residue, while bacteria regulate decomposition in cultivated soil.
An abundance of fungi is undisturbed soils mimics closely to the natural fungal balance in nature. Bacteria are secondary decomposers after the fungi start the process.
According to Neher, 1999, If the goal is to better soil food web and mimic natures diversity and sustainability, certain practices might help the succession to no-till fertility:
- Reduction or elimination of cultivation, heavy machinery, and general biocides.
- Incorporating perennial crops and organic material.
- Synchronizing nutrient release and water availability with plant demand and
- Monitoring biological activity.
The entire field does not need to be transformed by huge investments of inoculants or compost. Transplants can be grown in media containing a colony of bacteria, fungi and associates consumers. These soil plugs gradually amend the soil and reduces the need for broad scale treatments (Ingham, 1998). This practice may reduce disease pressure and replaced pesticides with stronger plants in a soil facilitated eco-system.
Perennial planting systems closely resemble the natural ecosystem communities. Incorporating perennial crops into annual crops systems, allows for the growth of organic matter and a proliferation of omnivore and predacious species, each suppressing disease pathogens. However with diversity being the goal, using multiple organisms needs some investigation, fungal-feeding nematodes will consume beneficial mycorrhizae too. Thus the diversity and spatial dispersion of the elements is considerable.
Mobile creatures in the soil play an important role in soil health. In concert with microflora, microfauna need to be considered and included in the agro-ecosystem underground. Soil tilth is improved with massive migrations and expansions of organisms in the soil. Soil water availability and containment is improved and allowing for nutrient ingestion, processing, and dispersal to plant uptake. Disease pressure is reduced as natural deterrents, consumers, and predators regulate populations of vector organisms and metabolize pathogens. Nitrogen and other nutrients are made available up in natural processes reducing leaching to sub soils. Microfauna knit complex webs of stable soil structure. Finally, the organic matter in soil is increased each growing season building deeper and richer topsoils resistant to erosion as water is absorbed and wind blown silt is collected. The growing field becomes a stable and rich resource for crop production reducing passes by soil compacting machinery and caustic chemical treatments. With the use of natural soil organisms and beneficial plants above and below the soil surface, soil depth and health improves and plant yields are increased in a resilient and sustained agro- ecosystem.
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