Effects of tillage practices on root characteristics and root lodging resistance of maize

Lodging is an important adversity affecting maize yield and quality in the world, especially under dense populations. A field experiment was conducted with two hybrids, Xianyu335 (XY) and Jingdan28 (JD) to study the influence of tillage practices on root system characteristics and their relationships with lodging resistance. The tillage practices included direct seeding of maize into stubble (ST), direct seeding with hilling (STH), rotary tillage before seeding (RT) and rotary tillage with hilling (RTH); the hilling was done at the jointing stage. The RT significantly increased the soil water content, number of nodal roots, root length density, average root diameter, axile root/shoot (RS) ratio and root width, decreased the penetration resistance (PR), centre of gravity height and ear position coefficient of plants, and enhanced vertical root-pulling resistance and tensile force of individual aerial roots. The grain yield was also highest and root lodging rate lowest under TR, followed by ST. Although hilling at the jointing stage tended to increase root number, root length density and average root diameter within the 40 cm depth, the RS ratio, root width and vertical root-pulling resistance decreased markedly, resulting to lower yields and poorer root-lodging resistance. The vertical root-pulling resistance was positively correlated with number of nodal roots and RS ratio, but negatively correlated with centre of gravity height of plants. The root lodging rate had weak positive correlation with PR which had significant negative correlation with number of nodal roots. This suggested that the poor root system of summer maize was the main reason of the weak root lodging-resistance and rotary tillage before seeding and direct seeding into stubble would be suitable practices for maize production while hilling could exacerbate root lodging and should be avoided. The knowledge obtained here will be useful for hybrid selection and improving cultural practices for enhancing the root lodging resistance of maize in rain and wind prone regions.