燕麦花生间作系统作物氮素累积与转移规律

Characteristics of crop nitrogen accumulation and nitrogen transfer in oat and peanut intercropping system

【目的】研究燕麦‖花生间作系统中燕麦和花生的地上部干物质和氮素积累、花生根瘤固氮酶活性、固氮量及花生向燕麦的氮素转移量,明确间作花生固氮特性及花生向燕麦的氮素转移规律,进一步探索间作体系下氮素的循环机理。【方法】本研究在大田不施用氮肥的试验条件下,通过采用随机区组试验设计的方法,设置不同种植模式(燕麦单作、花生单作、燕麦‖花生间作),采用传统挖根法和15N同位素标记法探索燕麦与花生的干物质积累量和氮素积累量,花生根瘤的生物固氮效率以及花生体内氮素向燕麦的转移规律。【结果】与单作燕麦相比,燕麦‖花生间作体系下,燕麦的地上部干物质量和氮素积累量均显著增加(P<0.05)。随着生育时期的推移,燕麦的地上部干物质量和氮素积累量在单作和间作模式下均呈现逐渐增加的趋势,成熟期达到最大值。成熟期,间作燕麦地上部干物质积累量比单作两年平均增加了40.6%,地上部氮素积累量平均增加了49.0%。间作花生的地上部干物质积累量与单作相比呈下降趋势,生育前期差异不显著,到成熟期,间作花生的干物质积累量两年平均比单作下降了20.6%(P<0.05)。开花结荚期间作花生的根瘤数和根瘤重比单作两年分别降低了21.3%和16.8%,单位质量的固氮酶活性平均降低了26.2%(P<0.05)。2011年和2012年,虽然在生理成熟期间作花生的固氮效率与单作相比分别提高了10.3%和37.1%,但花生生物固氮量分别降低了52.3%和26.3%(P<0.05)。2012年间作花生向燕麦的氮素转移率达到21.4%,转移氮量为15.3 mg/株。【结论】燕麦‖花生间作显著降低了开花结荚期花生单位质量的根瘤固氮酶活性,但提高了成熟期花生的固氮效率,促进了花生固氮能力的发挥,且在燕麦和花生共生期内,花生体内氮素可以转移到燕麦,从而增加了燕麦对氮素的吸收利用,实现地上与地下的相互调节和促进作用,因而,燕麦‖花生间作是东北农区农田生态系统优化氮素管理的重要途径之一。

【Objectives】In order to ascertain the interaction on nitrogen fixation and transfer from peanut to oat in the intercropping system of oat and peanut, field experiments were conducted for understanding the characteristics of nitrogen cycle under oat and peanut monocropping and intercropping system. 【Methods】The field experiments with the randomized block design were conducted in 2011 and 2012. Three planting patterns were designed including oat monoculture（TO）, peanut monoculture（TP） and oat and peanut intercropping（TOP）.Peanut roots were washed to investigate the nodule growth, the 15 N-isotope labeling was used to quantify N fixation and subsequent transfer in the intercropping system. Dry matter accumulation, N uptake efficiency,nitrogen fixation amount of peanut, nodule growth characteristics at the peanut podding stage and content of N transfer from peanut to oat were investigated. 【Results】Compared to the monoculture, the aboveground dry matter accumulation of oat was significantly higher under intercropping system, and the accumulated N in oats increased significantly in 2011 and 2012（P 0.05）. At the mature stage, the average dry matter accumulation of intercropped oats was increased by 40.6% in 2011 and 2012, respectively, and the average nitrogen accumulation amounts of oat were increased by 49.0%. The aboveground dry matter and the amounts of accumulated N of intercropped peanut were not significantly affected in the early growing stage compared with monoculture, but at mature stage, the average dry matter accumulation was significantly decreased by 20.6%. The average nodule numbers of intercropped peanut were decreased by 21.3% in 2011 and 2012, respectively, and the average weight of root nodules decreased by 16.8% in 2011 and 2012, respectively, the nitrogenase activities per unit weight of root nodules at the podding stage were significantly decreased by 26.2%（P 0.05）. Although the nitrogen fixation efficiencies of intercropped peanuts at the physiological maturity stage were increased by 10.3% and37.1%, the biological nitrogen fixation amounts were decreased by 52.3% and 26.3%, respectively. The N transfer rate from peanut to oat was 21.4% in the intercropping system, with N transferred amount of 15.3 mg/plant in2012. 【Conclusions】This study demonstrated that intercropping of oat and peanut was an efficient strategy to achieve higher nitrogen utilization for oat. Although the oat and peanut intercropping system decreased the nitrogenase activity of peanut root nodules and nitrogen fixation amount of peanut, N-transfer from peanut to oat was evident in this experiment. The oat and peanut intercropping system can also benefit dual directional regulation between above ground and below ground for crops simultaneously, and is one of the most significant ways to optimizing nitrogen management in the farmland ecosystem in Northeast China.