Corn and soybean genotypes with contrasting root system: response to fertilizer placement and tillage

Abstract

The effect of tillage on crop yield, early growth, and soil nutrient stratification can be influenced by fertilizer placement. In addition, deeper root systems can enhance the crop ability to uptake water and nutrients. A thorough understanding of how these factors interact can result in increased grain yields and profitability for the producer. Three studies were completed to describe and evaluate different aspects of crop root system and response to fertilizer placement and tillage. The objective of the first study was to characterize the root system of two genotypes of corn (Zea mays) and soybean (Glycine max (L.) Merr.) using image analysis in the greenhouse and in the field, as well as evaluate dry weight accumulation and nutrient uptake patterns by shoot and root plant parts for both crops. Two different genotypes of each crop were sampled during the growing season to access root characteristics such as biomass, length, surface area, average diameter and volume. Significant differences were found in corn where the P1151 AM hybrid had greater root length, surface area and volume than the P1105 AM hybrid. In soybean, the differences were found in nutrient uptake with overall greater nutrient uptake values for the poor drainage variety (PD) compared to the good drainage variety (GD). The objective of the second study was to evaluate the effect of fertilizer placement and tillage system on corn with different genotypes. Three fertilizer treatments were combined with two different corn genotypes selected based on contrasting root systems and two different tillage systems. The three fertilizer placements were sub-surface band, broadcast, and control. The two hybrids of corn used were a P1151 AM hybrid and P1105 AM hybrid. The two tillage systems were no-till (NT) and strip-till (ST). Corn hybrids showed different response in root biomass but did not show a consistent response in other characteristics evaluated. Broadcast and sub-surface band increased nutrient uptake and grain yields over the control but were not significantly different from each other. Tillage showed no difference in corn response. The objective of the third study was to evaluate the effect of fertilizer placement and tillage system on contrasting soybean genotypes. Three fertilizer treatments were combined with two different genotypes selected based on contrasting root systems and two different tillage operations. The three fertilizer placements were sub-surface band, broadcast, and control. The two varieties of soybean used were one recommended for poor drainage (PD) and one recommended for good drainage (GD). The two tillage operations were NT and ST. Soybean root biomass differences were observed by varieties. Sub-surface band treatment favored early soybean growth, biomass and P uptake at the V3 growth stage, but it did not turn into yield increase. Soybean grain yields did not respond to fertilization in this study. Yield was affected significantly by variety selection and response varies by site-year.