Relative effectiveness of various amendments in improving yield and nutrient uptake under organic crop production

In organic farming, artificial/synthetic inorganic fertilizers/chemicals are not applied to increase crop yields, but adequate amounts of nutrients are essential for sustainable high production from agricultural crops. Two 3-year (2008 - wheat, 2009 – pea, and 2010 - barley) field experiments were conducted on certified organic farms near Spalding (Dark Brown Chernozem – Typic Haploboroll) and Star City (Gray Luvisol – Typic Haplocryalf) in northeastern Saskatche-wan to determine the relative effectiveness of various organic amendments (compost, alfalfa pellets, wood ash, rock phosphate, Penicillium bilaiae, MykePro, or gypsum), and intercropping of non-legume (wheat, barley) and legume (pea) annual crops on seed yield, total biomass yield (TBY) and nutrient uptake in seed + straw of wheat, pea and barley. In 2008, seed yield, TBY and nutrient uptake of wheat increased (but small) with compost and alfalfa pellets. In 2010, seed yield, TBY and nutrient uptake of barley increased substantially with compost and alfalfa pellets and moderately with wood ash. Other amendments had little or no effect on crop yield and nutrient uptake. In 2009, there was no beneficial effect of any amendment on yield and nutrient uptake of pea, most likely due to fixation of N which is the most limiting nutrient in these soils. Intercropping of wheat or barley with pea produced greater seed yield and nutrient uptake per unit land area basis compared to wheat or barley grown as sole crops in most cases. In conclusion, our results suggest potential benefits in improving yield and nutrient uptake of wheat and barley from compost, alfalfa pellets and possibly wood ash, most likely by preventing deficiencies of some nutrients, especially N, lacking in these soils under organic farming. Our findings also suggest the need for future research to determine the feasibility of rock phosphate, Penicillium bilaiae, MykePro, gypsum or other amendments in preventing P and/or S deficiency in organic crops using soils extremely deficient in these nutrients.


Introduction
• In organic farming, inorganic fertilizers/chemicals are not applied to prevent nutrient deficiencies in crops to increase production, but adequate amounts of nutrients are essential for sustainable production.
• In the Canadian Prairies, most organically farmed soils are deficient in available N, many soils low in available P, and some soils contain insufficient available S and K for optimum crop yield.
• The N deficiency in soil on organic farms can be minimized by growing/green manuring N-fixing legume crops, but if soils are deficient in available P, K, S or other essential nutrients, the only alternative is to use external amendments to prevent these nutrient deficiencies.
• Manure/compost can provide these nutrients, but often there is not enough manure or it is uneconomical to apply manure in remote areas.On such soils, rock phosphate fertilizer, elemental S fertilizer, gypsum, wood ash or other amendments may be used to correct deficiencies of these nutrients.
• The information on the efficacy of organic nutrient sources in improving yield by preventing nutrient deficiencies in organic crops is lacking under prairie soil-climatic conditions.

Objective
To determine the feasibility of compost, alfalfa pellets, wood ash, Penicillium bilaiae, rock phosphate, gypsum, and MykePro in increasing yield, seed quality and nutrient uptake by preventing N, P, K or S deficiencies in crops grown on certified organic farms.• Amendments were broadcast on surface and all plots were rotovated to about 10 cm soil depth few days prior to seeding.Plots were seeded with a double-disc press drill at 17.8 cm row spacing.

Summary Experiment 1:
• In 2008, seed yield and total biomass yield (TBMY) of wheat increased with compost and tended to increase with alfalfa pellets, but in other treatments similar to the control.
• In 2009, there was no significant increase in seed yield of pea from any amendment, suggesting that organic amendments were not effective in improving yield of pea.
The TBMY showed increases in some treatments, but the differences were not significant.
• In 2010, seed yield of barley increased considerably with alfalfa pellets and compost, and moderately with wood ash, but no effect in other treatments.
• In 2008, total N uptake in seed and seed + straw of wheat increased with alfalfa pellets and compost, but in straw it increased only with alfalfa pellets, suggesting that N in some treatments became available to the crop in the first year of application.Total P, K, or S uptake in seed and seed + straw increased with alfalfa pellets and compost, but the increases were small.
• In 2009, there was no effect of any amendment treatment on total N uptake in seed.
Total N uptake in straw or seed + straw was highest with compost, suggesting that N in compost became available to the crop, but it apparently did not benefit seed yield.Total P, K, or S uptake in seed, straw, or seed + straw was highest with compost, suggesting that these nutrients became available to the crop from compost.
Experiment 2: • In 2008, seed yield and TBMY of wheat increased with compost and alfalfa pellets compared to the zero-amendment control, but no beneficial effect from other treatments.
• In 2009, seed yields of pea increased only with compost, and there was a good response of TBMY to compost and alfalfa pellets.
• In 2010, seed yield of barley increased considerably with alfalfa pellets, followed closely by compost, with moderate increase by wood ash, but no effect in other treatments.
• In 2008 and 2009, total N, P, K, or S uptake in seed, straw and seed + straw increased with compost and alfalfa amendment treatments, suggesting that nutrients in compost or alfalfa pellets became available to the crop in the growing seasons.

Conclusions
• Compost and alfalfa pellets increased crop yield and/or nutrient uptake, but rock phosphate, Penicillium bilaiae, wood ash and MykePro had little effect on crop yield and/or nutrient uptake.
• In summary, the results suggest the potential of some organic amendments in improving yield and nutrient uptake, most likely by preventing some nutrient deficiencies in organic crops.
• However, on the potentially P-deficient soil in Experiment 1, we expected seed yield increase from finely-ground rock phosphate, Penicillium bilaiae, or MykePro, but it did not happen.
• This was probably that the soil contained enough available P for organic crop production with low yield potential.Similarly, on the potentially S-deficient soil in Experiment 2, we also expected seed yield increase with gypsum, but it did not occur.
• Again, this was probably that the soil contained enough available S for organic crop production with low yield potential.
Two 3-year (2008 -wheat, 2009 -pea, and 2010 -barley) field experiments were established on certified organic farms in spring 2008.During the summer of 2007, the land was managed as tilled fallow in Experiment 1 at Naicam, and as green manure fallow in Experiment 2 at Star City.• Precipitation in the growing season (May, June, July and August) was below average, with little precipitation in May at both sites in 2008.The precipitation in the 2009 growing season was slightly above average, with little precipitation in May at Naicam, and near average, with low precipitation in May at Star City.

1 )Figure 2
Figure 2 Total biomass yield of wheat with various amendments applied in spring 2008, at Naicam, Saskatchewan (P-deficient soil -Experiment 1 established in spring 2008).