The value of the first year nutrient and lime content and fertilizer application cost savings from the
applied biosolids was estimated at almost $71 per acre (Table 6). Most of this value was from credit for
the 1.87 tons per acre of lime in the biosolids. No first year value was assigned to the nitrogen content of
the biosolids because nitrogen is not normally applied to soybeans. Soybeans, a leguminous crop, fix
nitrogen from the soil air and thus do not normally need any nitrogen fertilizer. However, soybeans will
take up nitrogen when it is available in the soil rather than expend the extra energy required to fix it from
the soil air. Thus, biosolids applied N is not wasted on soybeans.
|
Table 6. J. B. Cocke, Hanover County: Partial Budgeting Results____________________________________ | ||||
|
Units |
Units credited |
Unit price $ |
Total Acre $ | |
|
Added costs None Added returns None Reduced costs | ||||
|
182 lbs N/acre |
lbs |
0.00 |
0.23 |
0.00 |
|
216 lbs P/acre |
lbs |
35.00 |
0.30 |
10.50 |
|
30 lbs K/acre Fertilizer application cost |
lbs |
30.00 |
0.14 |
4.20 |
|
savings 1.87 tons/acre of calcitic lime |
acre |
1.00 |
5.50 |
5.50 |
|
applied expected to last at |
tons |
1.87 |
27.00 |
50.53 |
|
Sub-Total |
70.73 | |||
|
Reduced returns | ||||
|
None | ||||
|
_______Total savings (loss)_____ |
70.73 | |||
In 1997, the soybean crop averaged 39 bushels per acre (48 bushels per acre in 1996) in this field, in spite
of an overall shortfall of rain during the growing season—estimated at 5 to 6 inches per acre below
normal.
L. C. Davis Farm, New Kent County
The L. C. Davis farm is a small grains farm in New Kent County with conventional till corn followed by
small grains double cropped with no-till soybeans. Davis usually applies commercial fertilizer for corn at
the rate of 130 to 140 pounds N, 50 to 60 pounds P, and 30 pounds K. In spring 1997, before corn was
planted, an estimated 6.65 tons dry biosolids were applied to a 27.3 acre field, which had not previously
had biosolids applied to it. The field contains Bojac and the highly productive Pamunkey silt loam soils
and had a pH of 6.4.
The nutrient value and fertilizer application cost savings (for 70 percent of crop needs based on lowered
nutrient uptake from drought conditions) and seedbed preparation value resulting from the biosolids
application were estimated at almost $57 per acre (Table 7). The net value per acre was about $56 after
subtracting costs incurred to till 1.5 acres that were compacted as a result of unloading and spreading the
biosolids. Most of the $56 per acre value was from credits for nitrogen and phosphorous content in the
biosolids. However, a cost savings of $13.50 per acre was also credited because the biosolids provider
incorporated the material into the soil, which reduced seedbed preparation cost.