长期玉米连作下不同产量水平0—100 cm土层黑土与淡黑钙土理化性状差异

  【目的】  比较长期玉米连作条件下，0—100 cm土层黑土和淡黑钙土土壤物理和化学性状的差异，分析影响产量的主导因素，为黑土地保护与利用提供理论指导。  【方法】  在吉林省中部黑土区和西部淡黑钙土区，各选取玉米连作种植年限超过15年的代表性地块18个，在每个地块采集深度为0—10、10—20、20—30、30—50、50—70和70—100 cm的土壤样品，并进行土壤理化性状分析。按照高、中、低3个产量水平将土壤样品划分为3组，综合比较黑土和淡黑钙土不同产量水平0—100 cm土层土壤理化性状的差异。  【结果】  中部黑土0—100 cm土壤肥力指标均高于西部淡黑钙土，其0—100 cm土层土壤氮、磷、钾素储量分别为12.3、4.8、175.1 t/hm2，分别比西部淡黑钙土高2.4%、13.3%、43.5%。黑土和淡黑钙土20—100 cm土层有机质和全氮含量均以高产田最高；高产田与中产田耕层 (0—20 cm) 土壤全量和速效氮、磷、钾含量均明显高于下层 (20—100 cm)。中部黑土20—30 cm存在一个较明显的保水保肥层，30 cm以下土层的土壤理化性状与产量多呈显著相关，0—100 cm土层土壤pH为5.15～7.07，高产田土壤固、液、气三相比例更理想，0—100 cm各土层广义土壤结构指数 (GSSI) 的高低表现为高产田 > 中产田 > 低产田，高产田土壤含水量高于其他两个产量水平，高产田与中产田0—100 cm各土层土壤全磷含量较为接近，二者耕层速效钾含量明显高于低产田。西部淡黑钙土无明显的保水保肥层，20—30 cm土层的理化指标与产量密切相关，0—100 cm土层土壤pH为6.61～8.31，高产田70—100 cm土层硝态氮累积量仅占0—100 cm土体总量的5.2%，而中、低产田该比例分别为22.3%和22.7%，硝态氮下移趋势明显。黑土与淡黑钙土区0—20 cm土壤均呈现酸化趋势，尤其是黑土区低产田表层土壤酸化现象明显。  【结论】  中部黑土区30—50 cm土层土壤理化指标对产量影响较大，高产田20 cm以下土层养分持续供应能力是其实现稳定高产的重要保证。西部淡黑钙土区20—30 cm土层理化指标对产量影响较大，土壤结构是影响产量的核心指标，持续土壤培肥是实现高产的重要措施。

Differences of physicochemical properties of black and light chernozem soils in 0–100 cm soil layer with different yield levels under long-term maize cropping system

  【Objectives】  Soil physical and chemical properties of black and light chernozem soils under long-term maize cropping system were studied.  【Methods】  Eighteen representative sampling plots were randomly selected in long-term (>15 years) maize fields in central (black soil) and western (chernozem soil) regions of Jilin Province. In each plot, soils in 0–10, 10–20, 20–30, 30–50, 50–70 and 70–100 cm layers were sampled to analyze physicochemical properties. Soil samples were classified into three groups i.e., high level (HYL), middle level (MYL), and low level (LYL)] according to maize yield in each region. The differences in soil physicochemical properties across the soil layers and among different grain yield levels in black and light chernozem soil were analyzed.  【Results】  The overall soil fertility within 0–100 cm depth in black soil was higher than that of light chernozem. Soil N, P, and K contents within 0–100 cm depth of black soil were higher than those of light chernozem by 2.4%, 13.3% and 43.5%, respectively. Highest contents of soil organic matter and total N within 20–100 cm soil depth were observed in the plots of HYL in the two regions. In HYL and MYL plots, soil total and available nutrients in the topsoil (0–20 cm) were significantly higher than those in the deeper layers (20–100 cm). In black soil, an apparent soil nutrient and moisture storage section was found at 20–30 cm layer, and soil pH at 0–100 cm layer ranged from 5.15 to 7.07. The distribution of solid, liquid and gas in soil were close to the ideal situation. The value of the generalized soil structure index (GSSI) within 0–100 soil layer decreased with yield level (i.e., HYL>MYL>LYL). Soil water content in HYL plots was higher than those of MHL and LML plots. Total P content within 0–100 cm soil layer in HYL was close to that in MYL plots. Available K content within 0–20 cm soil layer in HYL and MYL were greater than that in LYL. No special section, which could play role in water and nutrient retention, was found in light chernozem; however, significant correlation was found between soil physico-chemical parameters of 20–30 cm layer and yield. Soil pH within 0–100 cm layer in light chernozem ranged from 6.61 to 8.31. The accumulation of nitrate in 70–100 cm layer in HYL plots accounted for 5.2% of the total soil storage in 0–100 cm layer. Obvious decrease in soil pH was found in the two soils, especially in LYL plots.  【Conclusions】  In the black soil region, the physico-chemical properties of soil within 30–50 cm layer were strongly correlated with maize yield. The capacity of soil nutrients supply below 20 cm soil layer in HYL plots was important for sustaining higher yield. In light chernozem soil region, maize yield significantly was correlated with the physico-chemical properties of soil within 20–30 cm layer. Of all the soil properties, soil structure and pH were the main factors that determined the yield. Sustainable soil feertility improvement was an important measure to achieve high yield.