鄂伦春旗耕地土壤有机质含量的时空变化趋势及其与大豆产量的关系

为全面分析鄂伦春旗土壤有机质含量随着时间推移发生的变化及在空间上的分布情况,比较该区域不同土壤类型有机质含量的差异,探讨土壤有机质和全氮含量之间的关系,对2008—2014年在鄂伦春旗域内均匀采集的7722个耕地土壤样品进行土壤类型判别及有机质、全氮含量测定,并与1986年全国第二次土壤普查数据进行对比,同时通过盆栽试验研究土壤有机质含量及施肥水平对大豆农艺性状和产量的影响。分别采用油浴加热重铬酸钾容量法和半微量凯氏定氮法测定土壤有机质含量和全氮含量。通过相同区域近30年间有机质、全氮含量的比较分析鄂伦春旗土壤肥力变化动态。盆栽试验供试品种为‘北豆26’,设置23.24、41.45、60.21、81.37、98.71 g/kg等5个土壤有机质含量水平,在大豆开花期、成熟期分别记载发育进度和农艺性状,收获后考种获得产量性状数据。近30年来,鄂伦春旗耕层土壤有机质含量平均由127.24 g/kg下降到64.82 g/kg,降幅达49.06%。对不同土壤类型有机质含量变化进行分析,发现沼泽土有机质含量由165.9 g/kg下降到67.89 g/kg,降幅为59.08%;暗棕壤由120.9 g/kg下降到63.83 g/kg,降幅为47.20%;棕色针叶林土由149.2 g/kg下降到103.79 g/kg,降幅为30.44%;草甸土由111.5 g/kg下降到66.61 g/kg,降幅为40.26%;黑土由88.7 g/kg下降到65.63 g/kg,降幅为26.01%。土壤有机质与全氮含量显著正相关。施用化肥对大豆的增产效果因土壤有机质含量而异,当土壤有机质含量高于81.37 g/kg时,化肥对大豆的增产作用效果不明显。鄂伦春旗耕层土壤有机质含量下降49.06%,表明缺少有效土壤培肥措施的耕种对土壤有机质消耗极大。不同土类有机质平均含量随耕作年限的延长而下降的幅度存在明显差异,其中沼泽土降幅最大,黑土降幅较小,暗棕壤居中。土壤有机质含量丰富的土壤,即使不施用化肥,也能获得较高产量。因此,提高有机质含量是提高土壤生产能力和农业生产效益的根本性措施。作者认为,轮作倒茬和秸秆还田是最重要的土壤培肥措施。

Temporal-Spatial Distribution of Arable Soil Organic Matter in Oroqen Banner and Its Relationship with Soybean Yield

To study the spatial and temporal dynamic of soil organic matter content of different soil types in Oroqen and the relationships between organic matter content and total N content, the soil organic matter and total nitrogen content of 7722 soil samples collected in Oroqen Banner in 2008-2014 were analyzed and compared with the results of local soil samples taken during The Second National Soil Census in 1986. Furthermore, a pot experiment with different soil organic matter contents was conducted to determine the effects of soil organic content on botanical characteristics, agronomic traits and yield of soybean. The content of soil organic matter and total N were determined by oil bath heating potassium dichromate volumetric method and semi-micro Kjeldahl method, respectively. There were five levels for soil organic matter content (23.24, 41.45, 60.21, 81.37, 98.71 g/kg), and two fertilizing levels (fertilizer application and no fertilizer) in the pot experiment and soybean cultivar ‘Beidou 26’ was used as material. Developmental rate and agronomic traits were investigated at flowering and maturity stage, and yield measurements were taken after harvest. The soil organic matter content of arable layer in Oroqen Banner was significantly decreased by 49.06% from 127.24 to 64.82 g/kg in recent 30 years. The changes of organic matter content in different soil types were analyzed: organic matter content of swamp soil significantly decreased by 59.08% from 165.9 to 67.89 g/kg; organic matter content of dark brown soil significantly decreased by 47.20% from 120.9 to 63.83 g/kg; organic matter content of brown forest soil significantly decreased by 30.44% from 149.2 to 103.79 g/kg; organic matter content of meadow soil significantly decreased by 40.26% from 111.5 to 66.61 g/kg; organic matter content of black soil significantly decreased by 26.01% from 88.7 to 65.63 g/kg. Soil organic matter and total nitrogen content showed an obvious positive correlation. The effects of chemical fertilizer application on soybean seed yield were dependent on the soil organic matter content and no increasing effects were found after the soil organic matter content reached 81.37 g/kg. Soil organic matter in Oroqen Banner decreased by 49.06%, showing that unsustainable farming consumed a lot of soil organic matter. Significant differences of organic matter changes over years were found among the soil types, i.e. swampy soil had the largest decrease, while black soil had the smallest decrease and the dark brown soil was in the middle. Soil rich of organic matter, even without chemical fertilizer application, can also produce a higher yield of soybean. Therefore, enriching the organic matter content is the fundamental measure to improve the soil productivity and agricultural production efficiency. The authors suggest that crop rotation and straw returning are the most important measures for elevating soil organic matter.