减量施氮对玉米-大豆套作系统中作物产量的影响

通过田间试验,研究了种植模式(玉米单作、大豆单作、玉米-大豆套作)和施氮水平(0、180、240 kg N hm–2)对作物产量和大豆光合特性、干物质积累的影响。结果表明,大豆叶片Pn、Gs、Ci、Tr和植株干物质积累量随生育时期的推移呈先增加后降低的趋势。与单作相比,套作处理大豆的Pn、Gs、Tr在V5期(玉米大豆共生期)显著降低,但在R2、R4、R6期(玉米收获后)无显著差异,地下部、地上部及总干物质积累量在各生育时期呈降低趋势,R4~R6期的作物生长率和经济系数则显著提高。玉米-大豆套作体系下,施氮显著提高了大豆花后叶片Pn、Gs、Tr和植株地下部、地上部及总干物质积累量,增加了大豆单株荚数和产量,与习惯施氮(240 kg N hm–2)相比,减量施氮处理(180 N kg hm–2)大豆的Pn在R4、R6期提高了3.57%、11.82%,总干物质积累量在R6、R8期提高了5.06%、10.21%,单株荚数、产量提高了8.30%、10.15%。减量施氮处理下,玉米-大豆套作系统的总产量最高,总经济系数为0.49,LER达2.17。玉米-大豆套作减量一体化施肥有利于提高大豆光合特性和干物质积累,提高大豆产量和玉米-大豆套作系统总产。

Effect of Reduced N Application on Crop Yield in Maize-Soybean Intercropping System

Maize-soybean strip relay intercropping pattern is widely adopted in Southeast China. Whereas the traditional fertilized measures used by farmers are not good for high yield of soybean. In order to get high yield for both maize and soybean in this system, a field experiment was conducted to investigate the effect of reduced N application on photosynthetic characteristics and dry matter accumulation of soybean, and the system crop yield. The experiment included three planting patterns (maize monocropping, soybean monocropping and maize-soybean relay strip intercropping) and three rates of N fertilizer application (0, 180, 240 kg ha^–1). The results demonstrated that, the net photosynthetic rate (P_n), transpiration rate (G_s), stomatal conductance (C_i), photosynthetic capacity (T_r), dry matter accumulation of soybean increased initially and then decreased in the later stage. Compared with soybean monocropping, the P_n, G_s, and T_r of intercropped soybean decreased significantly in the intergrowth stage (V5), but had no significant differences at R2, R4, and R6 stages. Although the below-ground, above-ground and total dry matter accumulation of soybean significantly decreased during the whole growth period, the crop growth rate from R4 to R6 stages and economic coefficient significantly increased. In the maize-soybean relaystripintercroppingsystem, N application significantly enhanced the P_n, G_s, T_r, dry matter accumulation, pod number per plant, and grain yield of soybean. Compared with the conventional N application (240 N kg ha^–1), P_n of soybean under the reduced amount of N application (180 N kg ha^–1) increased by 3.57% and 11.82% at R4 and R6 stages, respectively. Furthermore, the total dry matter accumulation increased by 5.06% and 10.21% at R6 and R8 stages, and pod number per plant and grain yield increased by 8.30% and 10.15%, respectively. Finally, the maize-soybean relay strip intercropping system possessed the highest yield under the N application rate of 180 N kg·ha^–1, with the economic coefficient and land equivalent ratio (LER) of 0.49 and 2.17, respectively. Taken together, the reduced N application in maize-soybean relay strip intercropping system can increase the yield of soybean and whole the system through improving soybean photosynthetic characteristics and enhancing dry matter accumulation.