Increase of planting density has been widely used to increase grain yield in maize. However, it may lead to higher risk of root lodging hence causing significant yield loss of the crop. The objective of this study was to investigate the effect of planting density on maize nodal root growth characteristics and to analyse their relationships to root lodging resistance. Field experiment was conducted in 2010 and 2011, using two maize varieties, Zhengdan 958 (ZD) and Xianyu 335 (XY), under three planting densities, viz., 4.50, 8.25 and 12.00 plants m^-2. The results showed the root failure moment, an indicator of root lodging resistance, was significantly affected by the planting density, the maize variety, as well as the crop developmental stages, and was decreased with increasing planting density. The number and the average diameter of the roots on the upper internodes (phytomer 5 to 8) were decreased with increasing planting density, whereas the maize variety had little effects on those variables. On the contrary, the root angle was less responsive to planting density but was significantly affected by the variety being that XY had larger root angle than did ZD. The root failure moment was linearly positively correlated with the total root number and the average root diameter on the upper internodes, indicating that a greater root number and a larger root diameter are important traits for enhancing root lodging resistance in maize plants.

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Root growth is related to its water and mineral uptake. The structure and architecture of the root system is influenced by soil properties. Better understanding of root architecture and growth dynamics of maize grown on black soil may lead to more efficient use of applied nutrients and water by maize. Maize (Zea mays L.), cultivar Yedan 13, was grown in a black soil field in large root boxes in 2007. Plants were regularly sampled and the following data were recorded: number of emerged roots per phytomer, mean length and maximal length of axile root per phytomer, maximum rooting depth of axile root per phytomer, and angle of axile root per phytomer by excavation methods. The distribution dynamics of root dry weight at different black soil depths, and vertical and horizontal distribution in large root boxes were measured. There were more axile roots on the upper phytomers than on lower phytomers. The number of roots on phytomers P8, P9 and P10 were 15.71%，24.82%, and 25.86% of total number of per plant, respectively. Angles of the axile roots on lower phytomers were larger than those on upper phytomers. The angle of the axile root on P2 was the largest (81.51°), followed by P4 (69.33°), P3 (56.9°), and P5 (56.06°). The angles on phytomers from P6 to P10 were smaller, ranging from 30.13-40.72°. Mean length, maximal length, and maximum rooting depth of axile root on each phytomer all increased with day after seeding (DAS). Mean length, maximal length, and maximum rooting depth of axile roots on lower phytomers were larger www.ccsenet.org/jas Journal of Agricultural Science Vol. 4, No. 2; 2012 ISSN 1916-9752 E-ISSN 1916 22 than those on upper phytomers. Mean length, maximal length and maximum rooting depth of axile roots on P3 were the largest (2.37 m, 2.92 m and 2.12 m at 90 DAS, respectively). Root dry weight in each soil layer increased with DAS; there was a rapid increase from 50 to 90 DAS. About 80 % of root dry weight was in the soil above 40 cm. The general trend of percentage of dry weight in total dry weight per plant decreased as the distance from the plant increased. Over 78 % of root dry weight in total dry weight per plant was within 20 cm in the horizontal direction from the plant, and less than 6% was in the 40 cm to 60 cm zone in the horizontal direction from the plant.

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According to the needs of water-saving carrier construction and assessment in the process of national water-saving society innovation pilot in Jinhua City, the index system, construction standard and assessment method of water-saving carrier construction are analysed and studied. Combined with the water-saving demand of urban and rural life, this paper puts forward the evaluation mode of four construction carriers of Jinhua water-saving community, school, organ and institution, hospital, which provides support for the construction of water-saving society in Jinhua City.