Effect of conservation tillage of wide/narrow row planting on maize root and transmittance distribution

A field experiment was conducted to explore maize yield variability in relation to canopy structure, root distribution and other factors under conventional tillage planting and wide/narrow row planting in 2007—2008. The results showed lower soil compaction under wide/narrow row planting than conventional tillage planting by 25.17%~52.04% after sub-soiling during the period from June 25 to September 20. In the upper 45 cm soil layer, soil compaction decreased by 14.08%~53.16%. The least soil compaction was in the 11~20 cm soil layer. Root dry matter under conventional tillage planting was 13.47% and 29.62% higher than that of wide/narrow row planting at milking and maturity stages, respectively. However, percent root matter in the deep layer under wide/narrow row planting was higher than that of conventional tillage planting. At the 15~30 cm soil layer, percent root matter under wide/narrow row planting was 6.59%, 8.21% and 9.00% at silking, milking, maturity stages, respectively. Similarly, percent root matter under conventional tillage planting was 5.21%, 7.48%, 5.42% for the 3 growth stages, respectively. While it was 2.30%, 2.61% and 3.24% at the 30~45 cm soil layer at the 3 stages under wide/narrow row planting, percent root dry matter under conventional tillage planting was 1.62%, 2.53% and 2.09%. Different varieties and rainfall distributions influenced root growth under wide/narrow row planting. Photosynthetical active radiation (PAR) at middle part of plants under conventional tillage planting was lower than that under wide/narrow row planting. However, PAR at bottom of plant on June 18, July 24 and August 29 under wide/narrow row planting was significantly higher than that of conventional tillage planting by 16.12%, 5.15% and 4.95%, respectively. Increasing plant density therefore increased PAR under wide/narrow row planting, which eventually enhanced photosynthetic efficiency.