Synergy of Cover Crops with Manure Application

Yield and quality of an oat cover crop was evaluated with and without an application of digestate. The study was conducted in two years on two separate fields. The oats were hand harvested and 3 samples were collected for each of the triplicated treatments. The results were evaluated based on harvested crop value (yield and quality) and how that would compare to potential feed value for milk production, as well as soil organic matter contribution if the crop had not been harvested.

The results show the synergy of feeding the cover crop and the soil microorganisms that enhance nutrient cycling and biomass production. A few highlights shown in Table 1 and Table 2 below.

  • Feed quality decreases (milk/ton) with digestate applied, but yield increases by about 40% to give a 33 to 50% increase in milk production per acre
  • Nutrient uptake is higher than nutrients applied from digestate, indicating increased microbial nutrient cycling
  • The amount of time required to increase soil organic matter by 1% is cut almost in half with the combination of cover crops and organic amendment.

Table 1: Cover Crop Oats with and without Digestate - Yield and Quality of Harvested Material (harvested Oct 13, 2016 and Nov 1, 2017)

Yield

Treatment (avg of 18 samples) 2016 Dry Weight (t/ac) 2017 Dry Weight (t/ac) % change
CC Oat
1.9
2.68
-
Digestate + CC Oat
3.2
4.43
~40

Yield and Quality*

Treatment (avg of 18 samples) 2016 Milk/ton (lbs) 2017 Milk/ton (lbs) 2016 Milk/ac (lbs) 2017 Milk/ac (lbs) 2016 $$/acre 2017 $$/acre
CC Oat
1,985
3,044
3,466
8,139
$1,190
$2,794
Digestate + CC Oat
1,916
2,691
7,298
11,547
$2,505
$4,090
-
3.5% decrease
14% decrease
-
-
52% increase
32% increase

*using Wisconsin MILK2013 and milk value = $0.78/L

Table 2: Cover crop Oats with and without Digestate - Biomass impact on Soil Quality

Above ground biomass only 2016 OM (lbs/ac) 2017 OM (lbs/ac) 2016 P205 (lbs/ac) uptake/ removal 2017 P205 (lbs/ac) uptake/ removal 2016 K20 (lbs/ac) uptake/
removal
2017 K20 (lbs/ac) uptake/ removal
CC Oat
3,514
4,908
21
35
89
129
Digestate + CC Oat
5,861
8,122
42
64
209
230

 

SOM Stable Carbon (lbs/ac) % change in SOM (above ground only) Years to incrase SOM by 1% (above ground only) With Root Biomass (estimate)**
Digestate only 101 0.005 200 yrs 200 yrs
CC Oat 422 0.022 - 0.023 44 - 47 yrs 26 yrs
Digestate + CC Oat 823 0.0038 - 0.041 24 - 26 yrs 15 yrs

** 1,685 lbs/acre (6" depth) of carbon from 8 wk oat growth (J. Environ Qual 30:1911-1918 (2001))

Digestate@ 3,600 gal/ac (4.2% DM; 2.6% OM, 0.35% N, 1866 ppm NH4-N; 0.07% P; 0.2% K 4:1 C:N) = 56-46-78 lbs/ac avail N-P-K


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca