Growth analysis of soybean under no-tillage and conventional tillage systems

Soybean [Glycine max (L,) Merrill] plants grown with no-tillage (NT) often appear smaller than those grown with conventional tillage (CT), yet the, pr oduce similar grain yield. Our objective was to test the hypothesis that th e early-season growth depression is offset by compensatory growth and chang es in plant development, A Zr field study was conducted at Urbana, IL, on a long-term tillage experiment. Grain yield, moisture, protein. and oil cont ent were similar for CL and NT treatments. Total plant, stem, leaf, and pod dry biomass were all initially about 15 to 20% greater under CT, but the d ifference declined until about R5 or R6; thus, compensatory growth did occu r. ht the initiation of sampling (V2) crop growth rate was about 20% greate r under CT, but the difference declined until about R2. The advantage shift ed to NT until about R6. Leaf area index (LAI) was greater for Cf until abo ut R4, Net assimilation rate was greater for NT unfit about R5. Increases i n early season crop growth rate for CT was due to increased LAI. Greater cr op growth rate for NT late in the season was due to increased net assimilat ion rate. Leaf weight ratio was larger for the CT crop until about R6, Spec ific leaf area was less in CT than NT. This work supports our hypothesis th at compensatory growth and alterations in plant development occur when soyb ean is grown in NT systems and helps to explain why grain yield does not de crease with NT even though early-season growth is affected.