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BBC Story on Organic Food.


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It'd be interesting to compare current and projected yields per acre for conventional vs some fixed definition of organic cultivation and see what the data suggest.


Comparisons of organic and conventional chemical farming systems


A survey of recent studies comparing the productivity of organic practices to conventional agriculture provides an excellent example of the wide range of benefits we can expect from a conversion to sustainable agricultural methods. The results clearly show that organic farming accomplishes many of the FAO’s sustainability aims, as well as showing promise in increasing food production ability.


Sustainable Agriculture Farming Systems project (SFAS) at UC, Davis.

An ongoing long-term comparison study, SFAS is an interdisciplinary project that compares conventional farming systems with alternative production systems that promote sustainable agriculture.


The study examines four farming systems that differ in crop rotation design and material input use: a 2-year and a 4-year rotation conventional system, an organic and a low-input system.


Results from the first 8 years of the project show that the organic and low-input systems had yields comparable to the conventional systems in all crops which were tested - tomato, safflower, corn and bean, and in some instances yielding higher than conventional systems (Clark, 1999a). Tomato yields in the organic system were lower in the first three years, but reached the levels of the conventional tomatoes in the subsequent years and had a higher yield during the last year of the experiment (80 t/ha in the organic compared to 68 t/ha in the conventional in 1996). Corn production in the organic system had a higher variability than conventional systems, with lower yields in some years and higher in others.


Both organic and low-input systems resulted in increases in the organic carbon content of the soil and larger pools of stored nutrients, each of which are critical for long-term fertility maintenance (Clark, 1998). The most important limiting factor in the organic system appeared to be nitrogen availability (Clark 1999b). The organic system relied mainly on cover crops and composted poultry manure for fertilization. One possible explanation for a lower availability in the organic system, is that high carbon inputs associated with nitrogen to build soil organic matter, thus reducing nitrogen availability for the organic crops. During the latter 2 years of the experiment, soil organic matter levels appeared to be stabilized resulting in more nitrogen availability. This was in agreement with the higher yields of organic crops that were observed during those last two years. The organic systems were found to be more profitable in both corn and tomato among the 4-year rotations mainly due to the higher price premiums (Clark, 1999b).


Farming Systems Trial at the Rodale Institute — Soybean study.

Initiated in 1981, the Farming Systems Trial compares intensive soybean and maize production under a conventional and two organic management farming systems.


The first organic cropping system simulates a traditional integrated farming system. Leguminous cover crops are fed to cattle and the resulting manure is applied to the fields as the main source of nitrogen. In the second organic system, the leguminous cover crops were incorporated in to the soil as the source for nitrogen before corn or soybean planting.


Corn yields were comparable in all three cropping systems (less than 1% difference) (Drinkwater, 1998). However, a comparison of soil characteristics during a 15-year period found that soil fertility was enhanced in the organic systems, while it decreased considerably in the conventional system. Nitrogen content and organic matter levels in the soil increased markedly in the manure—fertilized organic system and declined in the conventional system. Moreover, the conventional system had the highest environmental impact, where 60% more nitrate was leached into the groundwater over a 5 year period than in the organic systems (Drinkwater, 1998).


Soybean production systems were also highly productive, achieving 40 bushels/acre. In 1999 however, during one of the worst droughts on record, yields of organic soybeans were 30 bushels /acre, compared to only 16 bushels/acre from conventionally- grown soybeans (Rodale Institute, 1999). "Our trials show that improving the quality of the soil through organic practices can mean the difference between a harvest or hardship in times of drought" writes Jeff Moyer, farm manager at The Rodale Institute in Kutztown, Pennsylvania (Rodale Institute, 1999). He continues, "over time, organic practices encourage the soil to hold on to moisture more efficiently than conventionally managed soil." The higher content of organic matter also makes organic soil less compact so that root systems can penetrate more deeply to find moisture. These results highlight the importance of organic farming methods and their potential to avert future crop failures both in the US and in the rest of the world.


Broadbalk experiment at the Rothamsted Experimental Station, UK

One of the longest running agricultural trials on record (more than 150 years) is the Broadbalk experiment at the Rothamsted Experimental Station in the United Kingdom. The trials compare a manure based fertilizer farming system (but not certified organic) to a synthetic chemical fertilizer farming system. Wheat yields are shown to be on average slightly higher in the organically fertilized plots (3.45 tones/hectare) than the plots receiving chemical fertilizers (3.40 tones/hectare). More importantly though, soil fertility, measured as soil organic matter and nitrogen levels, increased by 120% over 150 years in the organic plots, compared with only 20% increase in chemically fertilized plots (Jenkinson, 1994).


Organic grain and soybean production in the Midwestern United States

A comprehensive review of a large number of comparison studies of grain and soybean production conduct by six Midwestern universities since 1978 found that in all of these studies organic production was equivalent to, and in many cases better than, conventional (Welsh, 1999). Organic systems had higher yields than conventional systems which featured continuous crop production (no rotations) and equal or lower yields in conventional systems that included crop rotations. In the drier climates such as the Great Plains, organic systems had higher yields, as they tend to be better during droughts than conventional systems. In one such study in South Dakota for the period 1986-1992, the average yields of soybeans were 29.6 bushels/acre and 28.6 bushels/acre in the organic and conventional systems respectively. In the same study, average spring wheat yields were 41.5 bushels/acre and 39.5 bushels/acre in the organic and conventional systems respectively.


When comparing the profitability of farming systems, the study found that organic cropping systems were always more profitable than the most common conventional cropping systems if the higher premiums that organic crops enjoy were factored in. When the higher premiums were not factored in, the organic systems were still more productive and profitable in three of the six studies. This was attributed to lower production costs and the ability of organic systems to outperform conventional in drier areas, or during drier periods.


The author of the report remarked: "What is most surprising is how well the organic systems performed despite the minimal amount of research that traditional agricultural research institutions have devoted to them." (Welsh, 1999).


Comparison of conventional and organic farms in California.

Lastly, a study which compared ecological characteristics and productivity of 20 commercial farms in the Central Valley of California gives us a better understanding of how a conversion to organic would fare in a commercial farm setting.


The farms compared had a fresh market tomato production. Tomato yields were shown to be quite similar in organic and conventional farms (Drinkwater, 1995). Insect pest damage was also comparable in both cases of organic and conventional farms. However, significant differences were found in soil health indicators such as nitrogen mineralization potential and microbial abundance and diversity which were higher in the organic farms. Nitrogen mineralization potential was three times greater in organic compared to conventional fields. The organic fields also had 28% more organic carbon. The increased soil health in the organic farms resulted in considerably lower disease incidence. Severity of the most prevalent disease in the study, tomato corky root disease, was found to be significantly lower in the organic farms (Drinkwater, 1995).


Much more here: http://www.cnr.berkeley.edu/~christos/articles/cv_organic_farming.html



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