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 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 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 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 Objective 1 • Estimate phosphorus removal by irrigated corn silage crops cultivated throughout Southern Idaho with variable soil test P concentrations Objective 2 • Identify effects of increasing soil test P on potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), and manganese (Mn) 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. 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 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 Locations of corn silage fields in Southern Idaho selected for sampling, by county. # of fields sampled County 2008 2009 Jerome 3 4 Twin Falls 4 4 Lincoln 3 2 Canyon 3 2 Cassia 3 2 Franklin 2 2 Gooding 2 5 Payette 1 0 Total 21 21 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. Variable Mean Std. Dev Minimum Maximum Yield (wet ton/acre) 31.7 7.0 15.7 47.2 Yield (dry ton/acre) 11.2 2.6 5.2 17.4 % dry matter 33.8 6.4 23.8 54.5 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) Mean Std. Dev Minimum Maximum P 2078 361 1163 3067 K 8885 2862 4385 16839 Mg 965 290 596 1660 Ca 1380 670 531 2791 Zn 12.7 4.1 6.2 27.3 Mn 24.7 12.0 8.5 57.2 B 4.6 1.8 2.5 12.4 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) Mean Std. Dev Minimum Maximum P 43.7 11.7 17.0 76.3 K 187 73.2 69.4 339 Mg 20.6 8.3 8.3 36.7 Ca 30.0 18.0 6.8 73.2 3500 y = 0.2276x + 2060.4 R² = 0.0009 Whole plant tissue P (ppm) 3000 2500 2000 1500 1000 500 0 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. 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 18000 Whole plant tissue K (ppm) 16000 14000 12000 y = -2.9768x + 8900.4 R² = 0.0031 10000 8000 6000 4000 2000 0 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. 1800 Whole plant tissue Mg (ppm) 1600 1400 y = 0.0078x2 - 3.4621x + 1152.5 R² = 0.1241 1200 1000 800 600 400 200 0 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. 3000 Whole plant tissue Ca (ppm) silt, loam & silt loam sandy loam & loamy sand 2500 2000 1500 y = -6.4411x + 1991.3 R² = 0.1529 1000 y = -2.4818x + 1233.5 R² = 0.09 500 0 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. Whole plant tissue Zn (ppm) 30 25 20 y = -0.012x + 13.395 R² = 0.0185 15 10 5 0 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. 70 Whole plant tissue Mn (ppm) silt, loam, and silt loam 60 loamy sand and sandy loam 50 40 y = -0.1275x + 38.259 R² = 0.219 30 20 10 0 y = -0.012x + 16.2 R² = 0.0108 0 20 40 60 80 100 120 140 160 180 200 220 Olsen P 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. 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 Acknowledgements • Dick Johnson – Idaho NRCS • Anna Carey – Soils technician • Josh and Jonathan Wisniewski – Dairy science support • UI Analytical Labs • USDA ARS – Kimberly, Idaho Thank you!