By Sjoerd Willem Duiker
This summer, some interesting differences show up between tillage and no-tillage treatments in our long-term tillage studies in Centre and Lancaster Counties. Tillage practices have been in place for 38 years in Centre County and for 12 years in Lancaster County.
This year, we planted soybeans in the tillage studies which are both in a corn-soybean-wheat/vetch rotation. The tillage types are chisel/disk (in both locations) or moldboard plow/disk/cultipack (in the Centre County study only). In the no-tillage treatments, we do not use any soil disturbance besides a coulter on the planter or drill. The soybeans in Centre County were planted with a planter on 30 inch rows and in Lancaster County with a John Deere drill.
The first observation was a distinct reduction in plant populations and early growth in the chisel/disked soil compared with the no-till fields in Lancaster County (Figure 1). This was due to heavy rain shortly after planting, which led to severe sealing and crusting in the tillage treatment. This soil is especially sensitive to sealing. It appears the surface silt loam soil has mostly disappeared due to heavy tillage over the past twelve years. This has resulted in a heavier surface texture (clay loam). With the low organic matter content, the soil easily seals up after heavy rain. This phenomenon shows the importance of residue cover and improving surface organic matter content so soil tilth and aggregate stability can improve to avoid soil sealing and crusting.
The second observation was potassium deficiency in the no-till plots in Centre County (Figure 2). Potassium deficiency showed up in spots in the field – usually parts of a row. The potassium soil test level was low in this field (75 ppm). Some potassium was applied in the spring but more is needed. Leaf test results were showing severe deficiency (0.32%) in the plants showing K-deficiency symptoms, and also some deficiency (0.77 %) in plants that were not showing K-deficiency symptoms (normal levels are 1.71-2.51 %). The soil was rather wet when the crop was planted, which led to sidewall compaction in the no-till plots.
After this wet period it became dry. This led to root restrictions at the early stages of growth in no-till plots. Sidewall compaction could be avoided in no-till by using fingered closing wheels or posi-close wheels. In this case, the fingered closing wheels were mounted on both sides of the rows but they were not crumbling up the soil but merely poking holes in the soil. It is expected that potassium deficiency symptoms will even out once the root system breaks through the sidewall. Whether this will result in a yield effect is still to be seen because moisture savings in no-till may prove to be an important yield determining factor this year as well.
Source:psu.edu