秸秆和秸秆炭对黑土肥力及氮素矿化过程的影响

为实现我国典型黑土区玉米秸秆有效还田与协同提高肥料氮素养分利用提供理论依据,以东北黑土区春玉米种植体系为研究对象,在4年田间连续定位试验基础上,利用15N示踪技术结合淹水培养试验,研究秸秆和秸秆炭对土壤肥力与氮素矿化的影响。试验共设5个处理:对照、单施化肥(N1)、N1+50%玉米秸秆(N2)、N1+100%玉米秸秆(N3)、N1+相当于50%玉米秸秆还田的玉米秸秆炭(N4)、N1+相当于100%玉米秸秆还田的玉米秸秆炭(N5)。结果表明:与N1处理相比较,N2、N3、N4、N5处理均增加了土壤有机质、全氮、速效磷、速效钾、碱解氮含量、微生物量碳和氮含量,且等量秸秆还田处理高于相当于等量秸秆还田的秸秆炭处理,其中100%秸秆还田分别显著提高微生物量碳和氮含量15.1%和23.1%(P0.05);不同处理方式综合土壤肥力指数(IFI)由高到低依次为N3N5N4=N2N1,秸秆、秸秆炭还田可显著提高土壤综合肥力(P0.05);土壤有机氮的矿化量和矿化率随着秸秆和秸秆炭还田量的增加而增加,其中N2处理分别显著提高了23.4%和22.9%,N3处理分别显著提高了53.0%和35.8%(P0.05);N2、N3、N4、N5处理下外源肥料15N的矿化量和矿化率分别显著提高了66.5%和50.0%、213.3%和279.0%、39.4%和36.3%、92.0%和40.0%(P0.05),且随着秸秆炭还田量的增加而显著增加。土壤氮素矿化指标与土壤有机质、总氮、碱解氮、微生物量碳氮含量都存在着显著正相关关系。研究表明玉米秸秆、秸秆炭还田均可以显著提高土壤综合肥力;可协同提高土壤氮素矿化水平,且提高来自外源化肥氮占土壤矿化总氮的比重,其中以100%秸秆还田处理的影响更为明显。

Effects of maize straw and straw biochar on soil fertility and the nitrogen mineralization process

The effects of maize straw and straw biochar incorporation on soil fertility and nitrogen mineralization in a typical black soil of Northeast China were studied to provide a theoretical basis for improvement of soil fertility and efficient utilization of nitrogen nutrients. A4-year field experiment, ¹⁵N tracing experiment, and flooding incubation experiment were carried out to study nitrogen mineralization characteristics under five treatments:chemical fertilizer (N1) as control, N1+50% maize straw (N2), N1+100% maize straw (N3), N1+50% maize straw biochar (N4), and N1+100% maize straw biochar (N5). Soil samples (0~20 cm) were collected and analyzed after maize harvesting.Incorporation of all the organic material combinations (straw and straw biochar) increased the soil organic matter, total nitrogen, available phosphorus, available potassium, and alkali nitrogen contents compared to the N1 treatment. Microbial biomass C and N also were enhanced under organic material incorporation conditions, with N3 treatment significantly increasing the microbial biomass carbon and nitrogen contents by 15.1% and 23.1%, respectively (P<0.05). Both the net soil nitrogen mineralization amount and rate were improved with straw or straw biochar incorporation. The Integrated Fertility Index (IFI) values of the different treatment methods were ordered from high to low as N3 > N5 > N4=N2 > N1, with straw and straw biochar return significantly improving the soil fertility. In addition, the N2 and N3 treatments significantly raised the mineralization amount by 23.4% and 53.0% respectively, and the mineralization rate by 22.9% and 35.8% (P<0.05). The nitrogen mineralization amount of exogenous ¹⁵N fertilizer also increased significantly under the N2, N3, N4, and N5 treatments by 66.5%, 213.3%, 39.4%, and 92.0% respectively, and the nitrogen mineralization rate increased by 50.0%, 279.0%, 36.3%, and 40.0% (P<0.05). The soil nitrogen mineralization index had significant positive correlations with soil organic matter, total nitrogen, alkali nitrogen, and microbial biomass. Maize straw and straw biochar incorporation significantly improved soil nutrient conditions and the microbial biomass in the black soil. The nitrogen mineralization rate also was enhanced under the same treatments. Moreover, maize straw or straw biochar incorporation could synergistically improve the contribution of exogenous ¹⁵N fertilizer to total mineralized nitrogen, especially with 100% straw return.