Soil Health Testing and Management 2015 PNW Direct Seed and Oilseed Conferrence Kennewick, WA January 21, 2015 WSU Columbia County Extension Paul G. Carter 1
Topics: Soil health Soil sampling for decision making Agronomic effects of poor soil health How do I get the health back?
Factors to good soil health. 1. Good Soil Structure 2. Neutral Soil ph (most plants prefer 6.2-7.3 ph) 3. Active, living microbial activity 4. Balance of 6 soil macronutrients (N, P, K, Ca, Mg, and S) 5. Balance of the 8 essential micronutrients (Cl, Fe, B, Mn, Zn, Cu, Mo, and Ni) 3
Soil ph and Acidity ph influences most inorganic chemical reactions Low ph - Affects nutrient availability in soil Deficiencies of certain nutrients (N, P, K, Ca, S, Mg) Toxicity of other nutrients (Aluminum, Iron, Manganese) 4
Low Soil ph - Crops at risk Lentils 5.6 Peas 5.5 Canola 5.5 Barley 5.2 Spring wheat Winter wheat 5.1 Triticale More Sensitive Less Sensitive 5
Soil ph and Nutrient Availability Soil ph % Fertilizer Efficiency N P K % Fertilizer Unavailable 5.0 53 34 52 54 5.5 77 48 77 33 6.0 89 52 100 20 7.0 100 100 100 0 Credit: Dr. Cliff Snyder 6
Soil ph Affects Availability of Plant Macronutrients 7
Aluminum Toxicity in wheat Poor root development Uneven crop growth and health Discoloration yellowing Increased drought stress Increased winter kill?
8.5 2014 8.0 7.5 7.0 ph 0-3 depth ph 3-6 depth Native Soil Sites 6.5 6.0 5.5 5.0 4.5 4.0 9
The 1980 survey found that only 9% of fields had ph values above 6.0. Where as 21% of the fields had ph values less than 5.2. The 2014 survey found that only 3% of fields had ph values above 6.0. Where as 23% of the fields had ph values less than 5.2. 2014 Columbia County survey soil ph values surface 12 inches Soil ph Percent of fields surveyed > 6.0 3 5.6 5.9 8 5.2 5.4 66 < 5.2 23 10
Stratified sampling identifies the location and extent of problem Sample Depth Sample Points 14 74 24 26 30 37 43 49 0-3" 6.80 6.30 5.60 5.50 5.10 5.20 5.70 5.30 3-6" 6.70 6.10 4.90 4.90 4.90 4.70 4.60 4.90 6-12" 6.60 6.20 5.7 5.8 5.6 5.3 5.4 5.9 0-12" 6.67 6.19 5.32 5.33 5.19 5.04 5.06 5.30 11
In field soil ph meters Use a soil ph meter to make instant field checks. Collect soil core Check soil column inch by inch Record soil ph results 12
No-Vegetation Area Vegetation Area 1 4.1 1 5.7 2 5.1 2 4.9 3 5.4 3 5.0 4 5.4 4 5.1 5 5.2 5 5.3 4.1 ph 5.7 ph 13
Problem Weeds Rattail Fescue Prickly Lettuce Horseweed Downy Brome Could soil acidity be a contributor to the increased problem of these weeds? Do weeds: Prefer the lower soil ph conditions? Tolerate the acid soil better than field crops? Have a competitive advantage with the crops due to acid conditions?
Adverse Herbicide Efficacy/Stability as Influenced by Soil ph Acidic Soil (ph<6.0) Imidazolinones Triazines Metribuzin Acetochlor Metalochlor Alachlor Alkaline Soil ph (ph >6.8) Triazines Metribuzin Sulfonylureas DNA s
Plant Diseases Cephalosporium Strip Wheat below ph 5.5 Fusarium Wilt Peas below ph 5.7 Pythium and Phytophthora Root Rot below soil ph 5.7 Disease incidence tends to be higher in reduced tillage systems, particularly in higher fertility acidic soils. Damping off and root rots caused by Pythium and Phytophthora are most problematic in acidic, poorly drained soils with a high organic matter content.
Reasons to Increase Soil ph Neutralize toxic elements: Al, Fe, Mn, H Improve overall nutrient availability Increase microbial activity Improve soil structure with Ca Improve Ca and Mg availability Overall, improve plant health Reduce weed competition Reduce disease imapct Maximize herbicide effectiveness Reduce herbicide carryover 17
How Lime Reduces Soil Acidity Ca 2+ ions from ag lime replace H + on soil exchange sites. The carbonate ions (CO 3 2- ) left over from ag lime reaction degrades in the soil solution, creating excess OH - (hydroxyl) ions which combine with H + ions forming water. This leaves H 2 0 and CO 2 The ph increases because the acidity source (H + ) has been reduced
Conclusions for a Healthy Soil Maximizing crop production by minimizing crop stresses. ph is perhaps the most overlooked and neglected aspect of crop production stresses. Collect soil samples or use ph meters to identify potential acid soil layers in the top one foot More than 95% of soils need some lime applications Some of weed/disease problems are due to poor soil conditions Herbicides are formulated for a neutral soil ph (6.2-7.3) condition Lime with CaCO 3 to raise soil ph
Questions Paul G. Carter Washington State University Extension 509-520-2719 cart@wsu.edu 20