Knowing the levels of nitrogen in your soil provides a base in which one can confidently decide on the amount of fertilizer that must be applied to achieve a desired yield. Similarly, being conscious of carbon levels in soil provides an indication of amendments required, such as manure or green manure (cover crops). To know how much N is available to the plant, a standard soil chemical test exposes soil samples from the field to a salt solution. The cations from the salt solution compete with cations on clay mineral surface exchange sites, thereby releasing N ions in solution. Extraction of nitrogen and/or carbon can also be achieved by combustion, where the soil samples are burned, and the emanating smoke is tested for C and N content. Soil chemical analyses will provide results for C as percentage of organic matter (%OM) and N as either ammonium (NH4+) and/or nitrate (NO3-) ions. The Haney soil analysis test, developed by Rick Haney at United States Department of Agriculture research station in Temple, Texas, is an alternative test to the standard soil chemical analyses for carbon and nitrogen. The Haney soil test replaces a salt solution with water as the extraction medium.
This project investigates methods to lower input costs and maximize profit, not necessarily yield. The rate of fertilizer applied to a crop should influence its growth and the amount of C and N readily available for the season. Cash crops such as canola, pea, and wheat were selected and sown under three different fertility levels (no fertilizer, 30%, and a 100% of the nitrogen rates recommended by the Haney soil test). This experiment was treated as a randomized complete block design and replicated four times. This trial will be conducted again in 2021.
There was no significant difference in canola yield when subject to either 0%, 30%, or 100% of the Haney soil test recommended fertilization levels (P=0.13). Applying 0% of the recommended nitrogen led to the lowest yield of 6.8 bu/ac; applying 100% led to the highest, 8.3 bu/ac. The C.V. is 54.8, too high for results to be accepted as reliable. As with other experiments, this is likely due to weather-induced stress.
Treatment yields all fell within the range of 6-9 bu/acre. There was no significant difference in pea yields when subject to either 0%, 30%, or 100% of the Haney soil test nitrogen recommendations (P=0.4). As with canola, the coefficient of variation coinciding with the pea yield analysis was high at 28.4. Consequently, the results are unlikely to be indicative of true treatment effects.
The mean weight yields from each of the three treatments spanned two bushels/acre (50 bu/ac to 52 bu/acre). Similarly, test weight values for each treatment were nearly the same, 63-64 lb/bu. There was no significant difference in wheat yield regardless of the level of nitrogen applied (P=0.98). Likewise, test weight values were not significantly different (P=0.47), nor were protein contents (P=0.85).