By Jim Halford, P.Ag.

January 28, 2003

Our farm is located 10 miles Southeast of Indian Head. The farm has a valley running through it which provides side hill fields which had been subject to water erosion. As well, we have varying qualities of soil from near beach sand to reasonable quality loam soils. Some fence lines were completely buried due to wind erosion in the 1930’s. We also have varying versions of salinity in different areas of the farm. These soil challenges created our early interest in soil conservation.

The predominant soil type on our farm is Oxbow Loam. This soil has about 50% sand and 16% clay. The recent land assessment places our best quarter section at just over $40,000. In crop insurance ratings we vary from G to L with H being the most common. This is the soil type I am going to provide data on today, but first some economics.

A quick summary since 1980 shows how the economics have moved to favor one pass minimum disturbance seeding on our farm.

1980 Zero Till cost a Net Extra $15.00 per acre.

• We utilized a disk seeding system
• Required two passes – i.e. separate fertilizer broadcasting or banding
• Quantity and price of herbicides used was high
• No yield increase was obtained.

• One pass fertilizing/seeding/packing
• Average 10% higher yields
• Average $10.00 per acre lower costs due to reduced fuel and herbicide costs
• Much of the gain was due to increased fertilizer efficiency and hence greater crop competition and reduced weed control costs.

2000 Net Benefit of $35.00 per acre.

• Further gains to one pass fertilizing/seeding/packing
• Average 12-15% higher yields
• Average $15.00 per acre lower costs; i.e. can use NH₃ at seeding, can use Preharvest Glyphosate in the system, etc.
• Additional gains over 1990 are due to new knowledge and ability to fine tune fertilizer and herbicide inputs.
• We also now have over 20 years of soil improvement which is providing improved crop results – especially in stress conditions such as drought or excess rainfall.

A specific aspect of the soil information from our farm which I am going to present is that it was all developed by independent researchers as follows:

In 1991, Charles Maulé conducted a water infiltration simulation study on our Zero Tillage fields as well as on the neighbour’s wheat/fallow field which was in summerfallow. Note in Table 1 how organic matter increased at the rate of about 1% for every five years of Zero Tillage.

(Fall, 1991)

Note: A total of 3.2 inches of water was applied in 1 hour.

With the simulated rainfall of 3.2 inches per hour, the summerfallow field had only 1.5" infiltrate and 1.7" runoff, while the 13 year Zero Till field had 2.7" infiltrate and only .5" runoff. Charles Maulé concluded:

In 1998 McConkey et al evaluated water movement in the samples they collected on our farm and an adjacent conventional-till wheat/fallow field. The soils were initially saturated and then additional water movement was measured. Table 2 shows the results. They noted with interest how the long-term no-till field actually has higher saturated hydraulic conductivity than the native grass samples and is three times as high as the conventional-till field.

McConkey et al further reported on Crusting and Infiltration

The soil surface under long-term no-till is more stable upon wetting than that under conventional till. This means the surface remains a packed arrangement of small clods or soil crumbs. This imparts good tilth and environment for seedlings. The improved structure under no-till can be clearly related to greater organic matter at the soil surface under no-till. Table 3 gives the percent of the soil surface that was stable under sudden wetting for our loam soil.

Because of greater stability under no-till, soils are much less likely to crust in heavy rains even without considering the added benefit of the surface residue mulch on reducing raindrop impact on the soil. This greatly improves infiltration under no-till when conditions cause surface crusting under conventional-till.

We see in Table 1 how organic matter increased substantially in the 13 years up to 1991. If we look at the results from samples taken in 1998, we can see in Table 4 how the soil in the Zero Till fields were 87.7 – 90.6% of the level of organic matter in Native soils. The Conventional-till soils were only 67.7 – 71.7% of Native.

In 1990, we noted that we had been able to grow high protein wheat which yielded about 45 bushels/acre with only 40 lbs of actual nitrogen/acre. This led Schoneau et al to investigate three of our fields, as well as a neighbour’s field which had been farmed with a 50/50 wheat/fallow rotation for approximately 100 years. The Nitrogen and Sulfur available in each field is shown in Table 5.

(Fall, 1990)

Note that the total level of nutrients available was not substantially different between wheat/fallow and Zero Till fields. The real discovery made was in the level of nutrients mineralized (i.e. converted into a plant-available form.) To determine these levels, the scientists washed the available nutrients from soil samples at the start of a laboratory incubation period and measured the nutrients released every three weeks, for a total of 12 weeks.

Table 6 shows that the Zero Till field had twice as much nitrogen mineralized as did the fallow/wheat field in the top 2 inches.

(Converted to plant-available form)

The following conclusion is taken from Schoneau and Greer’s study:

In 1998 McConkey et al determined the following levels of Total Nitrogen in the three soils sampled, as shown in Table 7.

Comparing the measured Nitrogen on knolls we see the 20 year Zero Till soil had over 1600 pounds more nitrogen than the conventional soil. At 25 cents per pound of nitrogen, this would be worth $400.00 per acre.

Analysis was made by McConkey et al of the amount of nitrogen which could be potentially released from the top three inches of the soil samples in a plant-available form.

The researchers used a "Hot - KCl" system to provide a quick analysis of the soil samples. The mg NH₄-N/kg of soil are presented in Table 8. This shows the 20 year Zero Till sample to be 94.0 – 94.9 percent of the native sample, while the Conventional Till sample is only 33.7 – 37.6 percent of the native.

McConkey et al further extended the Hot – KCl to a "Predicted Nmin" which is the N expected to be mineralized from soil using a more conventional incubation and is calculated from the existing relationship with Hot – KCl NH_{4 .} The approximate mineralizable N in pounds per acre is determined from the above after adjustment for soil bulk density. The results are presented in Table 9. This provides an approximation of the plant-available Nitrogen from the organic matter in pounds per acre.

Table 9 indicates an extra 50 and 63 pounds of Nitrogen could be available on the knolls and level areas of the 20 year zero till field than similar locations in the conventional-till field. This could be very significant if a pound of actual nitrogen fertilizer starts to cost 40 cents!

Brian McConkey noted, "if both fields started at the same place then the gain is remarkable."

As noted in Table 8, the native soil showed only a slightly higher level of predicted Nitrogen than the average for the 20 year zero till soil. Due to significantly lower bulk density of the native samples, the pounds of nitrogen potentially mineralized are lower. The comparison is not entirely fair so the specific results for the native soil sample are not presented in Table 9.

We are fortunate to have had an evaluation of our soils in 1990 and again in 1998. This yields an interesting evolution in the amount of carbon and hence CO₂ – which has been tied up in our soils. Table 10 presents this information for our knolls and Table 11 for our level soil area. Note the native and conventional-till field site are assumed to be unchanged for the last 20 years.

We can note clearly in Tables 10 and 11 that our biggest gain in Carbon, and hence tie-up of CO₂, has taken place in the latter 7 years on our soils.

Limited information to date suggests carbon (and hence CO₂) increases in a soil will be rapid in the first few years, then level out to a steady increase and then reach a maximum. Our results have been different. My best explanation is as follows:

In the first 13 years of Zero Tillage we had the following situation:

1. Used a disk drill with separate fertilizer application (broadcast or banding). No yield or volume of crop material increases occurred;
2. A few years of low volume of production due to dry conditions;
3. The system may have been slow to start a full cycling and most of our Carbon gain was probably over the last few years of the first 13 year period.

In the seven years 1991 – 97 inclusive, we had a series of years of high volume production even during dry seasons. Hence the additions to the Carbon levels were significant.

The soil changes I have presented are all factual. Let us now make a few assumptions as to what this Carbon sequestration could be worth. We will assume one tonne of CO₂ stored in the ground can be sold, as a credit, for $5.00 to some energy polluting company who needs an offset to cover their emissions of CO₂ until they can develop a "cleaner" energy production system.

If we use our numbers from Table 11 – the Level Areas of our fields – we can extrapolate the following as shown in Table 12.

Alternatively we could take 1000 acres of land which has stored 16.8T of Carbon per Hectare in the last 20 years. This Carbon Dioxide storage could be valued at:

To achieve optimum crop growth, organic matter increases, better water infiltration, and carbon accumulation, it is essential to optimize nitrogen fertilizer use. This is going to be an even bigger challenge given that one pound of actual nitrogen may increase from 20 cents to as high as 40 cents.

If your normal cropping system has routinely used 60 pounds of actual nitrogen per acre, this could increase nitrogen fertilizer cost from $12.00 to $24.00 per acre. However, you, your spouse or your banker may decide that all you can spend is $16.00 per acre. Your new challenge will be to optimize crop outputs with only 40 pounds nitrogen per acre.

This will require that you more closely examine your fertilizer placement choices. Fortunately we have moved a long way past the idea of broadcasting our nitrogen fertilizer in a zero till operation. Banding fertilizer replaced broadcasting as a much superior and reliable technology.

What farm managers need to consider now is some simple but important factors to optimize their nitrogen fertilizer use such as:

• Placing the fertilizer in the right place at the right time
• Fertilize the crop not the weeds
• Concentrate the fertilizer to reduce soil tie up
• Accurate distribution across the seeder.

A general recommendation is to seek out facts rather than follow advertising!

Utilization of forages in a crop rotation and being able to go directly back to annual crops will hasten soil improvement. Based on our experience, we would predict that 3 – 4 years of a forage crop would improve soils equivalent to 7 – 8 years of continuous annual crops grown under a low disturbance system. If you go directly from a forage to an annual crop with low disturbance one-pass seeding, you will retain a greater amount of the soil improvements and minimize weed problems.

Jeff Schoneau also noted that "Brome grass improved the mineralizable fraction of organic N and S to a level equal to the native prairie. Such results suggest that a grass period can quickly rebuild the mineralizable fraction of degraded wheat/fallow rotations."