A Comparison of Conventional, Low-Input and Organic Farming Systems: The Transition Phase and Long-Term Viability

A Comparison of Conventional, Low-Input and Organic Farming Systems: The Transition Phase and Long-Term Viability

Summary

Objectives
1. Compare four farming systems, with differing levels of dependence on external resources over a twelve year period, with respect to:
Abundance and diversity of weed, pathogen, arthropod and nematode populations.
Changes in soil biology, physics, chemistry, and water relations.
Crop growth, yield and quality as influenced by different pest management, agronomic and rotational schemes.
Economic viability
2. Evaluate existing and/or novel sustainable and organic farming tactics
3.Distribute and facilitate adoption of information generated by this project to all interested parties as it becomes available.

Abstract of Results
At the halfway point of a twelve-year multidisciplinary farming systems experiment comparing organic, low-input and conventional farming systems, yields for safflower, beans and wheat have stabilized across all systems and are equivalent, while corn and tomato yields continue to fluctuate.

Low-input corn yields have consistently outperformed conventional and organic yields for the last three years and the low-input corn appears to have the most efficient nitrogen uptake and use, while organic corn yields vary based on seasonal nitrogen availability.

Tomato yields have fluctuated considerably between years and systems, and the conventional tomatoes continue to outyield the low-input and organic ones, despite the use of transplants in the latter two systems.
Nitrogen availability appears to be less of a driving factor in the yield determination of low-input and organic tomatoes than it is in corn, although type and content of organic inputs can substantially affect other factors such as nitrogen leaching potential, and crop use and efficiency.

The transition period was clearly important for the soil microbial community. It took at least three years for microbial populations in the organic and low-input systems to reach consistently higher levels of biomass, and activity, presumably making them better able to turn over organic material and generate nutrients for the crops, than populations in the conventional systems. It was evident that rapid turnover of organic forms of nutrients by microbial populations in organic and low-input tomato plots in 1993 led to high tomato yields even under nitrogen immobilization conditions.

Beneficial nematodes have been consistently greater in the organic and low-input plots in the last few years, most likely as a result of cumulative additions of organic matter. Insect and pathogen pests have fluctuated primarily by season, crop and system, and are much more weather dependent than system driven.

Weed pressure has also fluctuated considerably over the six years, showing more significant seasonal than system differences. The determining factor for variation in weed pressure is type of chemical and mechanical control. Shifts in weed species have occurred in the systems, most likely as a result of differences in herbicides used and longer fallow periods in the conventional systems, leading to greater invasion of perennial species in the conventional plots, and an increase in grass species in the organic and low-input plots.

The conventional systems continue to return a higher profit than the organic or low-input systems (unless organic returns are calculated based on premium prices), although the year to year variability of costs and returns is very high in all four systems.

Economic Analysis
The design of a farm production system must take into account the costs of the inputs into the system and the resulting value of the output. Conventional agriculture has traditionally placed the greatest importance on yield maximization while alternative agriculture has emphasized minimizing inputs, and in particular, nonrenewable resources.

Averaged over the first five years of the project, the total production costs for all four systems are remarkably similar. These averages are misleading, however, because year to year comparisons demonstrate that the costs of low-input and organic systems can be either higher or lower than an analogous conventional system depending on the cover crop species selected, the number of operations used for ground preparation, method of cover crop incorporation, and the degree of substitution of hand labor for pesticides and fossil fuels. The reduced inputs in 1989 and 1991 succeeded in reducing relative costs but resulted in poor yields and lower profits for the low-input and organic systems compared to the conventional systems. Switching to transplanted tomatoes from direct seeded in 1992 onward substantially increased the cost of the low-input and organic systems with mixed success in yields.

Averaging over all crops within each system shows the conventional two-year system with the highest average gross income, the second lowest average cost and the highest profit of all of the systems. The conventional four-year system had the lowest costs as well as the second highest net returns and third highest gross returns when no price premiums were included for the organic crops. The low-input system has higher average costs than the conventional systems because of the difference in hand hoeing costs and the use of transplanted tomatoes. The organic systems had the lowest gross returns and the highest costs of all the systems resulting in a net loss of $2/acre over the first five years. However, when premium prices were included for the organic crops, the gross returns were only slightly behind the conventional two-year system and significantly higher than the other two systems.

Potential Contributions
Since tomatoes are the principle cash crop in all of the systems, it is imperative that profitability be maximized for this crop, especially in the low-input and organic systems. One practice that originally showed promise for increasing yields and profits in the low-input and organic tomatoes is transplanting. Extraneous circumstances in 1993 and 1994, however, confounded tomato yield data making conclusions about the transplants premature.

It has been difficult to find a winter cash crop in the low-input and organic system that will meet the agronomic and economic needs of the systems. Previous crops tested have all been economic losses, but in 1993 and 1994 the oats/vetch in this niche provided profits for the whole farm. The oats/vetch mixture may also help to reduce nitrate leaching following corn, as yield data has shown that the oats respond well to residual soil nitrate and may act as a "catch crop".

Soil and tissue fertility data from the corn and tomatoes suggest that low-input farming has good potential to reduce synthetic fertilizer inputs and costs.

Farmer Adoption
Changes observed and reported include greater interest in cover crops, legumes and crop rotations; increased organic acreage in field crops; increased monitoring by growers of water use/efficiency, pest thresholds and soil and crop nitrogen requirements; and heightened interest in a more holistic view of soil health. Agricultural equipment dealers have also begun demonstrating more of an interest in specialized equipment, specifically for tillage and non-chemical weed management. Some growers have specifically reported using transplanted tomatoes in organic production as a direct result of this work.

Operational Recommendations
Results from the first six years have provided information on transition strategies that might benefit growers as they decide to shift to reduced chemical input farming. Foremost is that a grower should plan a transition to low-input or organic farming based on a workable crop rotation, equipment realities and management skills. There may very well be a delay of several years before the soil microbial populations are able to optimally provide plant nutrients from organic inputs and fertilization strategies may want to reflect this delay. Good soil and cover crop management is critical at all times; a multifaceted approach to nitrogen fertility including cover crops, manures, composts, starters and foliars is probably the best strategy for reducing risk of nitrogen deficiencies. Results indicate that direct seeded tomatoes may not be the best crop to use in the early stages of a transition to low-input or organic farming systems; organic safflower, beans and corn all had higher yields than tomatoes in the early years of the transition. A successful transition strategy could include a slow reduction of inputs rather than an immediate shift to entirely organic inputs.
Some general recommendations are to begin incorporating residues, as opposed to burning, and growing green manure crops to start building high microbial biomass and active soil organic matter. Use of no-till or minimum till, whenever possible, would also build soil organic matter. The use of transplanted tomatoes in cover crop systems has high potential, as it allows for increased biomass and nitrogen fixation of the preceding cover crop. The use of herbicides is not warranted in many instances, as cultivation is frequently a cost effective alternative. Field weed history should be monitored regularly and herbicides used only as needed.
Reported in 1995