Research report from OSU's North Willamette Agricultural Research and Extension Center
Delbert Hemphill
OSU Dept of Horticulture, NWREC
Introduction
Vegetable seedling emergence is often hindered by cold soils and by soil crusting which results from destruction of soil surface aggregates by rainfall or overhead irrigation. Past experiments with anticrustants, materials which prevent breakdown of the surface soil texture, have shown that phosphoric acid banded over the seed row often improves emergence of small-seeded vegetable crops. This material is very caustic, however, and requires special spray equipment. This trial compared several possible anticrustants with phosphoric acid and water-sprayed check.
Methods
The materials applied and rates included 1) phosphoric acid, diluted 1:3 with water, applied at 367 gallons of diluted solution/sprayed acre; 2) ureasulfuric acid, diluted 1:3 with water, applied at 367 gallons of diluted solution/sprayed acre; 3) Condor Ag (sulfonated oil), diluted 1:300, at 5,270 gallons/sprayed acre; 4) Condor Ag, diluted 1:300, at 263 gallons/sprayed acre; 5) Super Humic-15 (humic acid derivative) diluted 1:1000, at 500 gallons/sprayed acre; 6) Super Shot-40 (humic acid derivatives plus surfactants), diluted 1:1000, at 500 gallons/sprayed acre; 7) water at 367 gallons/sprayed acre. 'Waldmann's Green' lettuce and 'Pioneer' carrots were seeded at approximately 12 and 10 seeds/foot, respectively on July 7, 1986. The anticrustants were applied in a 3-inch band immediately after seeding. Plot length was 20 feet and treatments were replicated four times in randomized block design. Stand counts were made on July 14 and July 18, 1986. A total of three inches of irrigation water was applied between seeding and the first stand count date.
Results
No treatment significantly increased lettuce stands, although stands on phosphoric acid treated plots tended to be higher than on the check plots. Ureasulfuric acid and Condor Ag at the high application rate significantly reduced stands. In the case of ureasulfuric acid, this may have been from reduced soil pH. The high rate of Condor Ag may have caused soil crusting. Soil impedance was not measured, but the soil aggregate structure was visibly destroyed by the high rate of Condor Ag.
Early carrot emergence was stimulated by phosphoric acid, but was not significantly affected by the other treatments (Table 1). All other treatments tended to reduce stands slightly. At the second evaluation date, check plot stands had surpassed those on phosphoric acid treated plots and ureasulfuric acid and the high rate of Condor Ag both had lower than average stands.
None of the new materials evaluated showed promise as an anticrustant. However, rates and methods of application need to be studied in more detail.
Table 1. Lettuce and carrot stands as affected by several seed row sprays, 1986 Treatment Lettuce Stand Carrot stand July 14 July 18 July 14 July 18 ----------------seedlings/10 feet---------------- Phosphoric acid 21.4 23.1 14.0 69.8 Ureasulfuric acid 4.4 4.6 1.5 31.5 Condor Ag, high rate 6.7 7.3 3.0 49.0 Condor Ag, low rate 17.6 17.7 2.3 69.0 Super Humic-15 18.1 18.5 2.8 68.5 Super Shot-40 17.1 18.0 2.5 79.5 Check 17.8 17.9 4.2 82.0 LSD(0.05) 8.6 9.0 5.3 45.6