Crop and Soil Management Issues Related to Forage Cation Levels J.B. Peters, K.A. Kelling, Soil Science Department University of Wisconsin - Madison

Influence of pH on Alfalfa, Marshfield 2000

Treatments Four K 2 0 levels – 0, 100, 200, 400 lbs K 2 O/a/year * Target pH levels –Marshfield: six levels – –Spooner: five levels – –Hancock: eight levels – * Applied after first cutting

Average Tissue P Levels

Average Tissue K Levels 3 rd cut, 1999

Average Tissue Ca Levels

Average Tissue Mg Levels

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K levels. Arlington, WI. 1 Ca (ppm) Exchangeable K (ppm) Treatment Control t/acre WB t/acre WB lb S/acre gypsum LSD NS48 gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton 1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue cation levels. Arlington, WI, st Cut TreatmentKCaMg % Control t/acre WB t/acre WB lb S/acre gypsum Pr > F gypsum = 65 lbs Ca/acreWB = 320 lbs Ca / ton

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K levels. Lancaster, WI. 1 Ca (ppm) Exchangeable K (ppm) Treatment Control t/acre WB t/acre WB lb S/acre gypsum LSD NS gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton 1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue cation levels. Lancaster, WI, st Cut TreatmentKCaMg % Control t/acre WB t/acre WB lb S/acre gypsum Pr > F gypsum = 65 lbs Ca/acreWB = 320 lbs Ca / ton

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K levels. Spooner, WI. 1 Ca (ppm) Exchangeable K (ppm) Treatment Control t/acre WB t/acre WB lb S/acre gypsum LSD NS gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton 1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue cation levels. Spooner, WI, st Cut TreatmentKCaMg % Control t/acre WB t/acre WB lb S/acre gypsum Pr > F gypsum = 65 lbs Ca/acreWB = 320 lbs Ca / ton

Wavelength (nanometers) Reflectance Light absorption NIRS Concepts

Wet chemistry mineral analysis compared to NIR estimation. 3 rd cut, Hancock, Regression EquationR2R2 P NIR = (0.255)(P WET )0.19 K NIR = (0.579)(K WET )0.58 Ca NIR = (0.891)(Ca WET )0.79 Mg NIR = (0.349)(Mg WET )0.41

Wet chemistry mineral analysis compared to NIR estimation. 3 rd cut, Marshfield, Regression EquationR2R2 P NIR = (0.056)(P WET )0.01 K NIR = (0.335)(K WET )0.60 Ca NIR = (0.884)(Ca WET )0.67 Mg NIR = (0.325)(Mg WET )0.68

Wet chemistry mineral analysis compared to NIR estimation. 3 rd cut, Spooner, Regression EquationR2R2 P NIR = (0.068)(P WET )0.01 K NIR = (0.581)(K WET )0.36 Ca NIR = (0.506)(Ca WET )0.59 Mg NIR = (0.457)(Mg WET )0.53

Using NIRS in Forage Testing General Recommendations General Nutrients DMyesLigninlimited CPyesAshlimited ADFyesCalimited NDFyesPno StarchyesKno FatyesMgno Bypass CP yesMiroMinno Soluble CPlimited ADF-CPlimited NDF-CPlimited

Summary Liming these acid soils was essential to optimize DM production, irregardless of K As soil K increased, tissue K increased and tissue Ca and Mg tended to decrease Annual applications of K resulted in a buildup of soil K and a decrease in soil test Ca and Mg

Summary, cont. As soil Ca increased, tissue K levels tended to decrease and tissue Ca tended to increase, especially on the lighter textured soil at Spooner Large applications of Ca resulted in a buildup of soil Ca and a decrease in soil test K

Summary, cont. Keeping soil test K levels in the optimum range appears to be the best strategy for keeping tissue K levels in acceptable ranges for use as dairy feed