The average effective topsoil depth is only 15.1 cm in northeast China (against an average of 16.5 cm in China) [7], much smaller than that in North America, which reaches 35 cm on average [7]. The shallow and compacted topsoil not only restricts the root development of plants, but hinders their absorption of nutrients and water. The poor soil properties also reduce their tolerance to abiotic stress, especially resistance against natural disasters [5] and [8]. Subsoil tillage is one of the most effective ways to break up a plow

pan in farming management [9], [10] and [11]. It can break up compacted layers, loosening the soil and deepening the topsoil without inverting it, increasing soil permeability [12]. Alectinib nmr As reported by many authors, subsoil tillage can play important roles in efficiently breaking up the plow pan [9] and [13], promoting water storage in the soil [14] and [15], adjusting the proportion of solid, liquid, and gas of soil, improving the structure and characteristics of topsoil [15], [16], [17] and [18], and improving the Z-VAD-FMK mw ecological environment for root development and root activities that enhance the anti-stress capacity of plants [19], [20] and [21]. Varsa et al. [22] concluded that deeper tillage could result in higher corn grain yield, especially in dry seasons. Currently, the time and method for subsoil tillage vary in different regions based on local production operations and included inter tillage [23],

[24] and [25], autumn tillage [26] and [27], and spring tillage [26], [27] and [28]. In northeastern China, most farmers are accustomed to inter tillage, which is integrated with fertilizer topdressing at the V6 or V7 stage. Wang et al. [5] developed

a technique of subsoil inter tillage and water conservation in maize production with high yield and high efficiency. Based on this technique, a (-)-p-Bromotetramisole Oxalate local standard was established (DB22/T1237-2011). However, most studies have been performed over only one or two years, with subsoil tillage depths mainly around 30 cm, and the results could not accurately reflect the contribution of the technique to grain yield and nutrient accumulation. In the present study, a four-year (2009–2012) experiment in the middle region of northeastern China was conducted to evaluate the impacts of different subsoil tillage depths on soil properties, nutrient (N, P, K) uptake, root morphology, and grain yield of spring maize. The aim was to characterize the effects of subsoil tillage on spring maize and thereby provide useful guidance for soil management coupled with appropriate machinery operations for sustainable crop production in the northeastern region. The experiment was conducted on the research farm of Jilin Academy of Agricultural Sciences, Gongzhuling city, Jilin province (43°29′55″N, 124°48′43″E) during 2009–2012. The field had been under continuous conventional maize management for many years before the experiment.