Effects of mulching practices on soil carbon, nitrogen contents, and grain yield, water and nitrogen use efficiencies of summer maize
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摘要: 垄作覆膜和秸秆覆盖有利于提高作物产量和降雨利用效率, 但覆盖对土壤碳、氮变化的影响仍不清楚。本文设置2年田间试验, 共3种处理: 垄作覆膜(RFM)、平作覆盖秸秆(SM)和平作不覆盖(NM), 研究覆盖措施对土壤碳、氮及夏玉米产量和水、氮利用效率的影响。结果表明: 与NM相比, RFM处理的5 cm 和10 cm 土壤温度分别显著提高0.5~1.0 ℃和0.2~0.7 ℃ (P<0.05), 加速了土壤有机碳分解, 显著减少土壤有机碳含量4.2% (P<0.05), 增强土壤呼吸速率33.2% (P<0.05); 而SM处理5 cm和10 cm土壤温度分别显著降低0.2~1.5 ℃和0.5~1.0 ℃ (P<0.05), 土壤有机碳含量增加21.3% (P<0.05), 土壤呼吸速率降低44.0% (P<0.05)。RFM处理中垄沟的土壤硝态氮含量大幅度降低(P<0.05), 而SM处理增加了0~80 cm土层土壤硝态氮含量(P<0.05), 减少了深层土壤硝态氮含量; SM和RFM最高分别增加土壤含水率23.8%和15.2% (P<0.05)、玉米氮素吸收增加37.6%和11.3% (P<0.05)。SM和RFM的地上部干物质积累、氮素收获指数以及作物耗水量均提高, 夏玉米产量分别提高16.8%和9.2% (P<0.05)、水分利用效率分别提高13.0%和9.1% (P<0.05)。覆盖秸秆通过增加土壤水分、有机碳含量和氮的有效性, 提高了夏玉米产量和水以及氮吸收利用效率, 是适合半干旱黄土高原雨养农业的有效覆盖方法。Abstract: Ridge furrows with plastic film mulching (RFM) and straw mulching (SM) are beneficial for improving grain yield and rainwater use efficiency; however, it is not clear whether they can affect the changes in soil carbon and nitrogen under continuous RFM and SM in the Loess Plateau of China. A 2-year field experiment (2019–2020) was established with three treatments, namely, RFM, SM, and no mulching (NM), to study the effects of RFM and SM on soil water and heat conditions, soil organic carbon and nitrate nitrogen contents, soil respiration rate, as well as summer maize nitrogen uptake, aboveground dry matter accumulation, evapotranspiration, soil water and nitrogen use efficiencies, and grain yield. Finally, a mulching method suitable for rainfed agriculture in the semi-arid Loess Plateau was proposed to provide a scientific basis for summer maize planting and environmental protection in this area. The results showed that compared with NM, RFM significantly increased the soil temperature by 0.5–1.0 °C at 5 cm soil depth and by 0.2–0.7 °C at 10 cm soil depth (P<0.05), accelerated the decomposition of soil organic carbon, significantly decreased the soil organic carbon content by 4.2%, and significantly enhanced the soil respiration rate by 33.2% (P<0.05). SM significantly decreased the soil temperature by 0.2–1.5 °C at 5 cm soil depth and by 0.5–1.0 °C at 10 cm soil depth (P<0.05), increased the soil organic carbon content by 21.3% (P<0.05), and decreased the soil respiration rate by 44.0% (P<0.05). Compared with NM, RFM significantly decreased the soil nitrate nitrogen content in the furrow (P<0.05). SM significantly increased the soil nitrate nitrogen content at 0–80 cm depth (P<0.05), but significantly reduced the nitrate nitrogen content in the deeper soil (P<0.05). The results showed that SM significantly increased the nitrate nitrogen content of the soil surface, promoted the supply of nitrogen, and reduced the residual nitrate nitrogen content as well as the leaching loss. SM and RFM significantly increased the soil water content by 23.8% and 15.2% (P<0.05), respectively; increased the plant nitrogen uptake by 37.6% and 11.3% (P<0.05), respectively; transferred more nitrogen to the grains; significantly increased the grain nitrogen uptake, nitrogen harvest index, and grain dry weight (P<0.05); increased the aboveground dry matter accumulation (P<0.05); significantly improved the grain yield of summer maize by 16.8% and 9.2% (P<0.05), respectively; and increased the water use efficiency by 13.0% and 9.1% (P<0.05), respectively. Mulching practices (RFM and SM) can increase the soil water content, plant nitrogen uptake, and grain yield. However, compared with RFM, SM was more effective in conserving soil water, increasing production, and reducing carbon dioxide emissions. SM could increase the summer maize nitrogen uptake and utilization as well as grain yield of summer maize by improving the soil moisture content, soil organic carbon content, and soil nitrogen availability. Therefore, SM is an effective mulching method for rainfed agriculture in the semi-arid Loess Plateau, China.
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图 1 2019年和2020年夏玉米生长季日气象数据
Figure 1. Daily meteorological data during summer maize growing seasons in 2019 and 2020
图 2 2019年和2020年不同处理夏玉米不同生育期土壤含水率变化
RFM为垄作覆膜, NM为平作不覆盖, SM为秸秆覆盖。*和**分别代表P<0.05和P<0.01水平3个处理间差异显著, ns代表P˃0.05。误差棒为不同处理标准误差的平均值。
Figure 2. Soil moisture contents at different growth stages of summer maize under different treatments in 2019 and 2020
RFM is ridge-furrow planting with plastic film mulching, NM is conventional planting without mulching, SM is conventional planting with straw mulching. * and ** mean significant differences among 3 treatments at P˂0.05 and P˂0.01, respectively, ns means P˃0.05. Bars indicate the averages of the standard errors of different treatments.
图 3 2020年夏玉米生长季当地相同日期日气温的变化和不同处理地温及土壤呼吸速率
RFM为垄作覆膜, NM为平作不覆盖, SM为秸秆覆盖。*和**分别代表P<0.05和P<0.01水平3个处理间差异显著, ns代表P˃0.05。误差棒为不同处理标准误差的平均值。
Figure 3. Local daily air temperature for the same date and soil temperature and respiration rate under different treatments during summer maize growing season in 2020
RFM is ridge-furrow planting with plastic film mulching, NM is conventional planting without mulching, SM is conventional planting with straw mulching. * and ** mean significant differences among 3 treatments at P˂0.05 and P˂0.01, respectively, ns means P˃0.05. Bars indicate the averages of the standard errors of different treatments.
图 4 2019年和2020年不同处理土壤有机碳及硝态氮含量变化
RFM为垄作覆膜, NM为平作不覆盖, SM为秸秆覆盖。不同小写字母代表同一年份不同处理间在 P<0.05水平差异显著。*和**分别代表P<0.05和P<0.01水平3个处理间差异显著, ns表示无显著性差异。RFM is ridge-furrow planting with plastic film mulching, NM is conventional planting without mulching, SM is conventional planting with straw mulching. Different lowercase letters represent significant differences at P<0.05 level among treatments in the same year. * and ** mean significant differences among 3 treatments at P˂0.05 and P˂0.01, respectively, ns means P>0.05.
Figure 4. Soil organic carbon and soil nitrate nitrogen contents under different mulching treatments in 2019 and 2020
图 5 2019年和2020年不同生育期不同处理夏玉米地上部干物质积累量
RFM为垄作覆膜, NM为平作不覆盖, SM为秸秆覆盖。不同小写字母代表不同处理间在P<0.05水平差异显著。误差棒为不同处理标准误差的平均值。
Figure 5. Dry matter accumulation aboveground of summer maize under different treatments at the jointing stage (S1), tasseling stage (S2), silking stage (S3), grain filling stage (S4) and maturity (S5) in 2019 and 2020
RFM is ridge-furrow planting with plastic film mulching, NM is conventional planting without mulching, SM is conventional planting with straw mulching. Different lowercase letters represent significant differences at P<0.05 level among treatments. Bars indicate the averages of the standard errors of different treatments.
表 1 2019年和2020年不同处理夏玉米百粒重、产量、吸氮量、氮素收获指数、耗水量及水分利用效率
Table 1. 100-grain weight, grain yield, nitrogen uptake, nitrogen harvest index, evapotranspiration and water use efficiency of summer maize under different treatments in 2019 and 2020
年份
Year处理
Treatment百粒重100-grain
weight (g)产量Yield
(t·hm−2)植株吸氮量
Plant nitrogen uptake (kg·hm−2)籽粒吸氮量
Ear nitrogen uptake (kg·hm−2)氮素收获指数
Nitrogen harvest index (%)作物耗水量
Evapotranspiration (mm)水分利用效率Water use efficiency (kg·hm−2·mm−1) 2020 NM 32.1±1.44c 9.34±0.15c 205.0±9.20c 99.6±6.79c 48.68 401b 23.0c RFM 33.5±2.25b 10.20±0.45b 228.2±8.43b 113.2±6.50b 49.64 410ab 25.1ab SM 34.9±2.10a 10.91±0.14a 282.1±10.86a 137.1±8.22a 51.87 421a 26.0b 2019 NM 32.3±1.27c 9.44±0.34c — — — 354e 26.7b RFM 33
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