1. PHOSPHORUS UPTAKE BY SILAGE CORN IN SOUTHERN IDAHO Amber Moore, Steve Hines, Brad Brown, Mario de Haro Marti, Christi Falen, Mireille Chahine, Tianna Fife, Rick Norell, and Jim Ippolito

2. Introduction 545,000 dairy cows in Idaho – Produce an estimated 12,000 tons of phosphorus every year – Applied to crops Corn silage – primary crop for P removal – Greater P removal potential than wheat, beans, potatoes, sugar beets, and other Idaho crops – Feed for cows

3. Idaho OnePlan (NRCS) recommendations Plans written from June 2007 to present – Estimate P tissue 0.185 % P, based on NRCS plant database – For 32 ton/acre yield, estimate P removal at 41.4 lb P /acre, or 94.8 lb P2O5/acre Plans written prior to June 2007 – Estimate P tissue 0.260 % P, based on national averages – For 32 ton/acre yield, estimate P removal at 58.2 lb/acre, or 133.3 lb P2O5

4. Soil test P and nutrient uptake Increased soil test P may – Increase potential for P removal, as has been seen in triticale – Induce Zn and Mn deficiencies, as has been seen in high applications of P fertilizer – Reduce Ca, Mg, and/or K uptake due to cation competition Need to determine if these effects are occurring – To account for them in the Idaho OnePlan software – To help growers avoid potential toxicities and deficiencies

5. Objective 1 Estimate phosphorus removal by irrigated corn silage crops cultivated throughout Southern Idaho with variable soil test P concentrations

6. Objective 2 Identify effects of increasing soil test P on potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), and manganese (Mn)

7. Site selection and description 42 corn silage fields sampled in 2008 and 2009 – Varying P fertilizer and manure application histories – 21 fields per year – Sub-sampled 3 plots in each field – Plot size - 2 rows X 10 ft.

8. Soil and tissue analysis Determine Olsen P of the soil at harvest Determine P, K, Ca, Mg, Zn, and Mn content of the corn tissue at harvest Determine harvested yield of each plot

9. Why test soil P at harvest only? Our goal is to determine if P uptake in the plant is influenced by the P content of the soil It was not our intent to look at a P budget Limited funds for study, could not afford to sample fields more than once per season

10. Locations of corn silage fields in Southern Idaho selected for sampling, by county. County # of fields sampled 20082009 Jerome34 Twin Falls44 Lincoln32 Canyon32 Cassia32 Franklin22 Gooding25 Payette10 Total21

13. Yield and dry matter for corn silage harvested from 42 in 2008 and 2009 throughout Southern Idaho with varying fertilizer and manure application histories. Soil test P varied from 3 to 300 ppm Olsen P. VariableMeanStd. DevMinimumMaximum Yield (wet ton/acre) 31.77.015.747.2 Yield (dry ton/acre) 11.22.65.217.4 % dry matter 33.86.423.854.5

14. Whole plant tissue analysis for corn silage harvested from 21 fields in 2008 and 21 fields in 2009 throughout Southern Idaho with varying fertilizer and manure application histories. Soil test P varied from 3 to 300 ppm Olsen P. Tissue (ppm)MeanStd. DevMinimumMaximum P207836111633067 K88852862438516839 Mg9652905961660 Ca13806705312791 Zn12.74.16.227.3 Mn24.712.08.557.2 B4.61.82.512.4

15. Nutrient uptake for corn silage harvested from 21 fields in 2008 and 21 fields in 2009 throughout Southern Idaho with varying fertilizer and manure application histories. Soil test P varied from 3 to 300 ppm Olsen P. Variable Nutrient uptake (lb/acre) MeanStd. DevMinimumMaximum P43.711.717.076.3 K18773.269.4339 Mg20.68.3 36.7 Ca30.018.06.873.2

16. Whole plant tissue P analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

17. P uptake recommendations Average P uptake – 44 lb/acre (for 32 ton/acre yield) Average tissue P conc. – 0.21% – 39 of 42 fields between 0.15 and 0.25% – Over 20 ppm, increasing soil test P up to 200 ppm with manure applications had not significant effect on P removal Recommend Idaho OnePlan use 0.21% P for P uptake estimates for newer and older plans – 0.185 % - may be underapplying based on P uptake – 0.260 % - likely overapplying based on P uptake

18. Whole plant tissue K analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

19. Whole plant tissue Mg analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

20. Whole plant tissue Ca analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

21. Whole plant tissue Zn analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

22. Whole plant tissue Mn analysis related to Olsen P for corn silage harvested from 21 locations in 2008 and 21 locations in 2009 throughout Southern Idaho.

23. Summary Recommend tissue P % for corn silage be changed to 0.21 % in the Idaho OnePlan Identified potential trends of decreasing Mn, Ca, and Mg with increasing Olsen P Identified possible soil texture affect on Mn and Ca relationship to Olsen P Need controlled studies to further evaluate relationships between soil test P, manure application, soil texture, and nutrient deficiencies/toxicities

24. Acknowledgements Dick Johnson – Idaho NRCS Anna Carey – Soils technician Josh and Jonathan Wisniewski – Dairy science support UI Analytical Labs USDA ARS – Kimberly, Idaho

25. Thank you!