Tillage practice and phosphorus fertilization effects on the distribution and morphology of corn roots

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anglais. No-tillage (NT) is agricultural practice recommended in context of conservation agriculture. Consequently, the NT management systems often cause the stratification of phosphorus (P) with depth with high concentrations of P at the upper soil profile depending on the rate of P fertilization, as well as the alteration of soil properties. As a result, corn roots distribution and morphology could be modified. However, little is known about how the root system in soil profile responds to different combinations of tillage and P supply. A study was conducted at L’Acadie (Québec, Canada), on a clay loam soil in 2014 to quantify the effects of different tillages and P fertilization rates on corn (Zea mays, L.) root distribution and morphology. This long term field experiment, initiated in 1992, is a split-plot device with principal factor of tillage (mouldboard plow (CT) and no-till (NT)) and sub-plot factor of P fertilization (0, 17.5 and 35 kg P ha-1 biennially applied) under a corn-soybean rotation (Ziadi et al. 2014). Root samples were collected at R1 (silking) stage by 8 cm diameter soil cores. Cores were taken up to a depth of 40 cm at 5 cm, 15 cm and 25 cm perpendicularly to the corn row and were cut out at 5 depths: 0-5cm, 5-10 cm, 10-20 cm, 20-30 cm and 30-40 cm. After washing and sieving, root length and surface area of 1st order (diameter >0.08 cm), 2nd order (diameter range from 0.02 to 0.08 cm) and 3rd order (diameter < 0.02 cm) roots were measured on scanned image with the software WinRHIZO (Regent Instruments Inc., Quebec, Canada). The root distribution and morphology pattern in the soil profile showed no significant differences between NT and CT. The 35 kg P ha-1, biennially applied, tends to increase RLD by 27% and 43% to the fertilization of 0 and 17.5 kg P ha-1 as well as the root surface area (27% and 49%, respectively).