长期施肥对华北平原农田土壤呼吸及碳平衡的影响

Soil respiration and carbon balance in farmland ecosystems on North China Plains

在具有21年历史的长期定位试验地,研究了土壤温度变化、不同施肥处理对土壤释放CO2及小麦(Triticum aestivum L.)、玉米(Zea maysL.)吸收CO2量的影响,进而明确在华北平原小麦-玉米轮作制的农田生态系统中碳素平衡问题。研究表明:土壤释放CO2的量与土壤温度呈明显的正相关,相关系数分别达到r=0.717**(5cm地温)和r=0.764**(10cm地温)。进一步研究表明:在小麦生育期,施氮、磷各处理土壤释放CO2的数量随气温而增加,氮、磷肥配合的各处理与对照和单施氮、磷肥处理之间有显著的差异(P<0.05);但是2个处理组合(氮、磷肥配合、单施氮、磷肥)之内各处理之间差异不显著。土壤温度在10～20℃之间单施氮、磷肥无助于改变土壤释放CO2的量,而氮、磷肥配合施用可以明显地增加土壤释放CO2的量。不施肥与单施氮、磷肥处理麦田土壤呼吸释放的CO2量大于小麦固定的CO2量,向大气净排放的CO2量达0.83～3.73thm-2,而氮、磷肥配合处理的麦田从大气中净吸收的CO2量达7.89～12.49thm-2。在玉米生育期,土壤释放CO2的量在7月中旬达到最高值(12.40～22.52g·m-2·d-1),9月中旬降到最低(6.19～8.20g·m-2·d-1)。施用N540kg·hm-2·a-1,P2O5135kg·hm-2·a-1的处理(N2P2)释放的CO2量与施用N270kg·hm-2·a-1的处理(N1)之间差异不显著,与其它各处理之间差异显著(P<0.05),表明在玉米生育期长期施用高量氮、磷肥明显地影响到土壤释放CO2的量。玉米不但可以吸收土壤释放的CO2,还要从大气中吸收大量CO2,即在玉米生育期的农田生态系统可以降低大气中CO2的含量。总之,在华北平原小麦-玉米轮作制的农田生态系统土壤呼吸不会增加大气中CO2的含量,相反则有可能减少其含量。

This paper reports a study of the influence of soil temperature and fertilizer treatments on CO2 release and absorption by wheat and corn in a 21 year long-term experiment, and defines the carbon balance in the farmland ecosystem of wheat （Triticum aes- tivum L.）-com （Zea mays L.） rotation in North China plains. The results indicate that the amount of CO2 released in soil is correlated to soil temperature （r=0.717＊＊ in the 0-5 cm layer; r=0.764＊＊ in the 5-10 cm layer）. During the wheat growing period, the amount of CO2 released in the soil in every treatment that received nitrogen or phosphorus increased with increasing temperature. There was a significant difference between the fertilized treatments （i.e. fertilized nitrogen and phosphorus） and the control （including： only fer- tilized nitrogen or phosphorus） （P 〈 0.05）, but there was no significant difference between the fertilized nitrogen and phosphorus treatments, or CK and only fertilized nitrogen or phosphorus treatments （P 〉 0.05）. The amount of CO2 released in soil was higher than that absorbed by wheat in the control and nitrogen only or phosphorus only treatments. The net amount of CO2 released to at- mosphere was 0.83 - 3.73 CO2 t.hm-2. In the nitrogen and phosphorus treatments, there was a net absorption of CO2 7.89 - 12.49 t·hm2 from the atmosphere. In the corn growing period, the amount of CO2 released from the soil reached a maximum of 12.40- 22.52 g.m-2 d1 in mid July and decreased to a minimum of 6.19 - 8.20 g.m2-d-1 in mid September. The amount of CO2 released in the N2P2 treatment （i.e. N 540 kg＇hm2.a-1 and P205 135 kg·hm2·a-1） was not significantly different from the N1 treatment （i.e. N 270 kg.hm2.al）, but was different from the other treatments （P 〈 0.05）. Corn not only absorbed the CO2 released from the soil, but also absorbed it from the atmosphere, resulting in a net CO2 reduction in the atmosphere. In conclusion, soil respiration does not increase CO2 contents in the atmosphere, by contraries could decrease its net contents in the farmland ecosystem of wheat-corn rotation in North China plains.