Helen Atthowe, Biodesign Farm
Alex Stone, Oregon State University
This article is part of the Biodesign Farm Organic System Description
Strategies and tools
|I. Soil organic matter building1||See also Living Mulch and Organic Residues.|
|Optimize quantity of soil organic matter (SOM)||Increased from an average of 3.5 to 5.7% in Old field and from 3.3 to 5.2% in New Field.|
|Optimize quality of soil organic matter||Diverse organic residues were added regularly throughout the growing season. Organic residues varied in carbon content and ease of decomposition.|
|Maintain soil cover1||An annual or perennial legume/weed/grass living mulch was grown between vegetable crop rows.|
|Use winter cover crops||Winter cover was maintained by the year-round annual or perennial living mulch between crop rows. Total acreage in winter cover ranged from 50 to 75%.|
|Use summer cover crops||Summer cover was maintained by the year-round annual or perennial living mulch between crop rows. Total acreage in summer living mulch ranged from 30 to 50%.|
|Apply organic soil amendments and residues||Residues included mowed clover/weed living mulch, on-farm-made compost (stopped in later years), and alfalfa meal (later years only). Some materials were surface applied annually (mowed living mulch), and some were incorporated into crop rows in the spring (living mulch, compost, and alfalfa meal).|
|Apply manure-based compost||On-farm-made sheep or cattle manure compost was applied in Old field from 1993 through 2002 (Disease Table 2) and in 2006 and 2007 in New field (Disease Table 3). No compost was applied from 2008 through 2010. Manure was obtained at no charge from neighboring ranches.|
|Apply plant-based compost||No plant-based compost was available to purchase, and Biodesign did not have the materials to make a plant-based compost economically. On-farm clover and off-farm straw were added to the on-farm-made manure-based compost.|
|Apply organic amendments with varying carbon:nitrogen ratios||Organic residues with different C:N ratios (mowed living mulch residue and on-farm-made compost) were added spring, summer, and fall.|
|Reduce tillage||Minimum tillage was practiced in the spring (Old field) and only in crop rows (New field).|
|Diversify soil biota with crop and non-crop diversity1||The living mulch contained diverse annual and perennial species with different rooting types and depths, and different plant families (Table 4).|
|Grow a living root in the soil year-round1||The annual and perennial living mulches maintained year-round presence of legume, weed, and grass roots.|
|Mow weeds to enhance nutrient cycling||Weeds were a major component of the perennial and annual living mulch, which was mowed two to six times per year.|
|Till weeds to enhance nutrient cycling||Weeds were incorporated along with the living mulch each spring in Old field and in crop rows only in New field.|
|Apply organic nonliving mulches, such as straw||None applied. Mowed residue from living mulch row middles was sometimes blown into crop rows with the mower.|
|Maintain animals/livestock as part of the cropping system||Sheep from a neighboring farm grazed on crop fields during the winter in some years until 2004.|
|II. Soil fertility building||
Table 2 shows Biodesign's soil health trends, targets, and amendments.
Nitrate-nitrogen, potassium, and phosphorus trends are shown in Fig. 3 (Old field) and Fig. 4 (New field).
See also Living Mulch and Organic Residues, Table 3, and Table 5.
|Match nitrogen supply to crop need||Organic residues were applied gradually throughout the season to cycle/recycle nitrogen; some had higher C:N ratios. In some years, soil N levels were very high in the spring (May) when frozen soils thawed and organic residues were tilled into the soil; by the end of the growing season (September), they dropped. N may have been stored in perennial living mulch plant root/foliage biomass during the growing season and over the winter. N levels in clover living mulch foliage were tested and found to be relatively high in September.|
|Optimize soil potassium levels||K levels increased and were too high in the Old field until 2006 when they came down to a level within the target range. Old field levels were low, but came up to the target range. % K levels in clover living mulch foliage were tested and found to be relatively high in September.|
|Optimize soil phosphorus levels||P1 levels increased steadily to very high (excessive) levels in Old field and to target levels in New field. % P levels in clover living mulch foliage were tested and found to be relatively high in September.|
|Optimize soil calcium levels||Ca increased from an average of 1,588 to 2,024 ppm and decreased from 77.9 to 68.7% in the Old field. New field: Increased from an average of 1,485 to 1,790 ppm and decreased from 78.8 to 77.1%.
|Optimize soil magnesium levels||
Mg increased in the Old field from an average of 225 (1993) to 254 ppm (2006) . Percent of cation balance increased from 18.4 to 18.7%. New field: Increased from an average of 202 to 248 ppm. Percent of cation balance decreased from 18 to 17.8%.
|Optimize soil micronutrient levels||Soil micronutrient levels were tested in 1994. All were in the moderate to high range, except boron (0.6 ppm) and copper (0.8 ppm), both of which were low. In 1996, micronutrients were tested in the white clover living mulch foliage; all levels were in the sufficient range.|
|Optimize soil cation exchange capacity (CEC)||Increased from 10.2 to 16.8 meq/100g in Old field and from 9.8 to 11.7 meq/100g in New field.|
|Optimize soil cation balance||Biodesign's target was 65–70% Ca, 15–20% Mg, and 3–5% K. In Old field, ending ratios were on target: 70% Ca, 18.7% Mg, and 5.7% K. In New field, they were 77.1% Ca, 17.8% Mg, and 5.1% K.
|Optimize soil pH||In Old field, soil pH increased from 6.9 in 1993 to high levels of 7.7 in 1999 then decreased slightly to 7.6 in 2004-2006. In New field, pH remained relatively stable at about 6.8.|
|Apply off-farm soil amendments and fertilizers before planting||Gypsum (22% Ca, 16% S) was applied in New field once in 2007, at a rate of 100 lb/4-ft x 600-ft row. When compost addition was stopped, alfalfa meal was added to crop rows in New field from 2008 through 2010, at 50 lb/4-ft x 600-ft row.|
|Apply off-farm soil amendments and fertilizers as a crop side-dress||None applied.|
|Apply foliar minerals and fertilizers||None applied.|
|Apply foliar compost teas||Helen experimented with compost teas in the early 1990s, but stopped using them in the late 1990s.|
|Rotate crops||Crops were rotated by crop family (Solanaceae, Brassicaceae, Fabaceae) in a 3-year rotation.|
|Use soil tests to measure soil trends||Helen sampled soil for analysis every 1 or 2 years and did monthly soil tests during the growing season in 1995, 1996, 2006, and 2007 during on-farm experiments to test the effect of the living mulch and organic residue amendment system on nutrient cycling.|
|Optimize irrigation to minimize evapotranspiration (ET) loss2||Biodesign used drip irrigation and sprinklers. Vegetables received 1 to 1.5 inches/week.|
¹Strategy listed in the NRCS Soil Quality Initiative
²ET can be determined with the use of CIMIS data, in-field soil moisture measurement, or both.
|Soil health indicator||Trend||Biodesign target||Status/Trends (1993–2010)||
|Soil organic matter (SOM)||UP||3.5% minimum for Biodesign's sandy loam soils||Increased from an average of 3.5 to 5.7% in Old field and from 3.3 to 5.2% in New field.||On-farm-made compost was applied annually at 2 to 12 tons/acre (Disease Table 2 and Table 3). Compost application decreased and was stopped in later years (2003 in Old field, 2008 in New field).|
|Cation exchange capacity (CEC)||UP||10–15 meq/100g||Increased from 10.2 to 16.8 meq/100g in Old field and from 9.8 to 11.7 meq/100g in New field.||Residues derived from the mowed living mulch were incorporated and surface applied applied annually (Table 3).|
|Nitrate-nitrogen (NO3)||UP & DOWN||30–40 ppm during early years; 20–30 ppm in later years||Old field: Increased from an average of 15 ppm (1993) to 102 ppm (1996), falling again to 33 ppm (2006). Nitrate-N levels were related to manure compost application rates. New Field: Increased from lows of 13 ppm (1993) to highs of 47 ppm (2010) in minimum-till crop rows.
||Alfalfa meal was added to crop rows in New field only (2008–2010) at 50 lb/4-ft x 600-ft row.
|Potassium (K)||UP & DOWN||200–300 ppm; 3-5% of cation balance||Old field: Increased sporadically from an average 145 ppm (1993) to 713 ppm (2003), falling again to 323 ppm (2006). Potassium levels were related to manure compost application rates. Cation balance ended at 5.7%. New field: increased from 123 ppm (1993) to 229 ppm (2010). Cation balance ended at 5.1%.
|UP||40–90 ppm||Old field: P1 levels increased steadily from 9 ppm (1993) to very high levels of 192 ppm (2006), even after manure compost applications were decreased in 1999 and stopped after 2002. New field: Increased from 8 ppm (1993) to 55 ppm (2010).
Supporting data is from regular soil tests taken from an average of multiple samples per year at the 0- to 12-inch depth. All samples were taken in May with a 3/4-inch-diameter, 10-inch-long soil probe and were analyzed by A & L Western Agricultural Lab, Modesto, CA.
|Month||C:N ratio||N (%)||S (%)||P (%)||K (%)||Mg (%)||Ca (%)||Fe (ppm)||B (ppm)||Zn (ppm)|
¹Average of three samples each month in July, August, and September
²Bennett, W. F. 1993. Nutrient deficiencies and toxicities in crop plants. APS Press, St. Paul, MN.
|Weed species||Weed life cycle1||Untilled pasture||Minimum-till||No-till||Containers|
¹ A = annual
B = biennial
P = perennial
|Year||N (%)||P2O5 (%)||K2O (%)||S (%)||Mg (%)||Ca (%)||Na (%)||Fe (ppm)||Al (ppm)||Mn (ppm)||Cu (ppm)||Zn (ppm)||Moisture content (%)|
|1995||Cattle Manure Compost¹||0.65||0.43||0.57||0.12||0.25||1.16||0.03||1,073||747||99||6||22||60.2|
|2006||Sheep Manure Compost²||0.67||0.49||0.82||0.14||0.26||1.31||0.07||1,233||538||114||7||23||61.8|
¹1995 Compost was made with cattle manure, straw, and clover
²2006 Compost was made with sheep manure, straw and clover
|Treatment2||Organic matter||Nitrogen||Phosphorus||N:P Ratio||Potassium||Magnesium||Calcium||pH||CEC|
¹New field was 60-year-old grass/weed/clover pasture before tillage.
²Three samples per treatment were analyzed 2 weeks after tillage. Samples were taken 15 April 2005 from 0-10 inches with a 3/4-inch-diameter, 10-inch-long soil probe. Ten samples were taken, mixed in a bucket, and a two cup sample was sent for analysis. This was repeated for a total of 3 soil tests per each of the two treatments. Samples were analyzed by A & L Western Agricultural Lab, Modesto, CA.
|Test/Method code||Results (mg/L)||Date analyzed||Critical value|
|Nitrate EPA 300.0||< 0.60||17 Jul 20001||10 mg/L|
|Nitrate EPA 300.0||< 0.50||4 Sep 20102||10 mg/L|
¹Test performed as part of USGS Water-Resources Investigations Report 99-4219, Hydrogeology and Aquifer Sensitivity of the Bitterroot Valley, Ravalli County, Montana.
²Test performed for home inspection during farm sale.
This article is part of the Biodesign Farm Organic Systems Description.
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