Amir Sadeghpour1, Sarah Hetrick1, Karl Czymmek1,2, Gregory Godwin1, Quirine Ketterings1
1Cornell University Nutrient Management Spear Program, 2PRODAIRY
Introduction
Surface application of manure (i.e. without incorporation) to meet corn nitrogen (N) needs adds more phosphorus (P) than what corn and subsequent sod crops together can remove. This leads to buildup of P over time. To reduce the risk of long term soil test P (STP) buildup to excessive levels, at some point, manure rates need to be curtailed. Spring injection or immediate incorporation of a lower rate of manure increases the N-value of the manure and can avoid N limitation by a lower manure rate. The question addressed here is how effectively can switching from high rate of manure (N-based) to low rate with immediate incorporation (P-removal based) reduce STP buildup during five corn silage years?
Field trial
An experiment was conducted from 2001 to 2006 in a field with no prior manure history in Aurora, NY. The study had six treatments each replicated five times totaling 30 plots. Treatments were: (1) low rate of composted dairy solids (P-based; 20 tons/acre), (2) high rate of composted dairy solids (N-based; 32 tons/acre), (3) low rate of liquid dairy manure with immediate (within one hour) tillage incorporation (P-based; 7,000 gals/acre), (4) high rate of liquid dairy manure application (N-based; 21,000 gals/acre), (5) a zero N control (0 lbs N/acre) and (6) side-dress inorganic N (urea ammonium nitrate) at the recommended rate of 100 lbs N/acre. Field preparation consisted of chisel-plowing, disking, and cultimulching prior to planting silage corn. The low rate of manure received an extra pass of chisel-plow (two passes in total) to conserve ammonia-N.
Results
Phosphorus balance: Application of P with low rates of manure and compost (P-based) was designed to meet 90 lbs P2O5/acre removal a year. The actual yearly P removal was 63 lbs P2O5/acre with the low rate of compost and 35 lbs P2O5/acre for low rate of manure, reflecting lower than anticipated yields and a lower P2O5 content of the corn (Table 1). The high rate of manure had the highest 5-yr average annual P balance (151 lbs P2O5/acre per year) and shifting to a low rate of manure decreased the P2O5 balance by 77% (Table 1). Changing the high rate of compost to a low rate of compost reduced the P2O5 balance by 45%. Both low rates of manure and compost were showing balances above zero (lower corn silage yield than anticipated) so we would expect an increase in STP in all four treatments.
Soil test phosphorus: Compared to the initial levels (10 lbs P/acre), the high rate of manure led to a four-fold increase in STP as compared to a two-fold increase with a low rate of manure (Fig. 1). The highest STP increase occurred with the high rate of compost (6x), while the low rate of compost resulted in a three-fold increase in STP consistent with differences in P balances. Lower application rates resulted in slower buildup but because annual balances were positive for both application rates, an increase in STP took place for both the high and the low rates. Soil test P buildup with compost was faster (11 lbs P2O5/acre increased STP by 1 lbs/acre) than manure (25 lbs P2O5/acre increased STP by 1 lbs/acre) suggesting differences in nutrient sources in increasing STP over time (Fig. 2). Soil test P remained unchanged for inorganic N management. These data suggest that STP levels increase faster with compost application than with liquid manure application.
Conclusions
With water quality concerns, managing STP levels to reach, but not exceed, the agronomic optimum range will be increasingly important. This experiment shows that increases in STP levels can be better managed with appropriate conservation of manure N, allowing for lower overall rates. In addition, this research shows the importance of maintaining accurate yield records so actual P removal rates can be established and the importance of accurate manure records so management decisions can be made that focus on achieving P balance over crop rotations for soils in the agronomic optimum STP range.
Relevant References
- Sadeghpour, A., Q.M. Ketterings, G.S. Godwin, K.J. Czymmek. 2016a. Nitrogen vs. phosphorus-based manure and compost management of corn. Agronomy Journal 108: 185-195.
- Sadeghpour, A., Q.M. Ketterings, F. Vermeylen, G.S. Godwin, K.J. Czymmek. 2016b. Soil properties under nitrogen- vs phosphorus-based manure and compost management of corn. Soil Science Society of America Journal doi: 10.2136/sssaj2016.03.0086.
Acknowledgments
This material is based upon work that is supported in part by Federal Formula Funds and the National Institute of Food and Agriculture, USDA, under Award no. 2013-68002-20525. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the USDA. We thank Aurora Ridge Dairy Farm for providing the liquid manure. Composted dairy solids were supplied by Willet Dairy (years 1 and 2) and Fessenden Dairy (years 3 through 5). For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.
