秸秆焚烧对土壤有机质和氮磷钾含量的影响

Effects of wheat straw burning on content of soil organic matter,nitrogen,phosphorus,and potassium

秸秆露天焚烧作为对废弃秸秆常见的处理方式在中国普遍存在。目前的研究多集中在焚烧对区域大气环境的影响,对土壤环境的化学效应研究较少。因此,为揭示大田秸秆焚烧对土壤生物化学性质的影响,设置不焚烧(CK)、减量焚烧(A1)、全量焚烧(A2)、增量焚烧(A3)4个处理,通过连续4个月的田间小区定位试验,探究不同小麦秸秆焚烧量对耕层0—5 cm土壤有机质含量、微生物数量、土壤养分含量的即时效应和各指标在玉米各生育期内的变化情况。结果表明:小麦秸秆焚烧1 d后土壤有机质含量和微生物数量相对于CK显著降低(P<0.05)。其中,有机质含量在焚烧后减少11.0%—22.1%,真菌数量降低30.8%—56.1%,细菌数量降低50.6%—72.6%,放线菌数量降低46.9%—68.3%。土壤全效和速效养分含量显著增加(P<0.05):全磷含量增加6.5%—12.9%,全钾含量增加4.6%—18.1%,全氮含量增加2.6%—13.2%。速效磷含量增加9.8%—39.1%,速效钾含量增加13.2%—39.1%,铵态氮含量增加8.6%—38.7%,硝态氮含量增加1.4%—9.2%。各指标的变化幅度随焚烧量的增多而加大(A3>A2>A1)。玉米生育期内,焚烧处理的土壤有机质含量平均恢复5.6%(A1>A2>A3)。与有机质相比,焚烧处理土壤微生物数量恢复程度较高,其中细菌的恢复速率最快。在玉米苗期各焚烧处理的真菌、细菌和放线菌平均数量相对于CK依次降低12.7%、17.4%、11.9%,在大喇叭口期和成熟期,微生物数量与CK间差异不显著。速效养分含量在玉米生育期显著高于CK。在玉米苗期、大喇叭口期和成熟期,相对于CK速效磷含量平均增加24.9%、27.0%、29.2%,速效钾平均增加24.0%、14.1%、15.2%,铵态氮平均增加25.5%、23.1%、20.2%,硝态氮平均增加20.8%、19.2%、19.8%。

As a common treatment of waste straw, open straw burning is widespread in China, especially during harvest seasons every year. Recently, many studies have focused on the effect of straw burning on the regional atmospheric environment. However, there is relatively limited data on the change in the biochemical properties of soil. In order to better evaluate the effects of field straw burning on soil organic matter content, microorganism quantity, and soil nutrient content, a 4-month field trial was initiated in 2013. In the experiment, 4 treatments were used with different amounts of wheat straw： reduced burning （0.24 kg/m2, as Al ） , normal burning （0.48 kg/m2, as A2） , and incremental burning （0.72 kg/m2, as A3） , and no burning （as CK）. The effects of burning treatments on soil organic matter content, microorganism quantity, and soil nutrient content were measured by analysis of soil samples from 0--5 cm depth of topsoil, which were collected 4 times on June 13th （one day after straw burning）, July lOth （maize seedling stage）, August 15th （maize tasselling stage）, and October 8th （maize maturity stage）. The results showed that there were significant changes in soil organic matter content, quantities of fungi, baeteria, and aetinomyeetes, as well as total and available P, K, and N due to the different burning treatments. The immediate effeet of straw burning on these indicators was marked. The burning treatments had adverse influenees on soil organie matter and mieroorganisms. Compared with the CK treatment, soil organie matter content decreased by 11.0%--22.1%. The quantities of fungi, bacteria, and aetinomycetes decreased by 30.8%--56.1%, 50.6%--72.6%, 46.9%--68.3%, respectively. Soil total and available nutrient content inereased significantly （P 〈 0.05）. The content of total P, total K, total N, available P, available K, nitrate nitrogen, and ammonium nitrogen increased by 6.5%--12.9%, 4.6%--18.1%, 2.6%--13.2%, 9.8%--39.1%, 13.2%--39.1%, 8.6%--38.7%, 1.4%-- 9.2%, respectively. Meanwhile, the study found these indicators showed an increasing trend with the increase of burned wheat straw amount, namely in the order A3 〉 A2 〉 A1. Throughout the growth period of maize, soil organic matter and microorganism quantity in the three burning treatments recovered to different extents, After the maize growth period, compared with the previous stage after burning, soil organie matter content in burning treatments recovered 5.6% on an average in the order A1 〉 A2 〉 A3. The microorganism population restored to a higher degree than that of organic matter. Bacteria had the fastest reeovery rate among the three microbes. In the maize seedling stage, the quantity of fungi, baeteria, and actinomycetes in the burning treatments was 12.7%, 17.4%, 11.9% lower than that of CK, respeetively. At the maize tasselling and maturity stage, the microorganism quantities had no significant differences between the burning treatments and CK, whieh indicated that the microbial quantities had reached the normal level two months later after burning. Soil available nutrient content in the burning treatments was higher than that of CK during the maize growth period. At the seedling, tasselling, and maturity stage, compared with the CK, the available P eontent increased by an average of 24.9%, 27%, and 29.2%; available K eontent increased by an average of 24%, 14.1%, and 15.2%; ammonium nitrogen content inereased at an average of 25.5%, 23.1%, and 20.2%; and nitrate nitrogen eontent inereased at an average of 20.8%, 19.2%, and 19.8%, respectively.