不同质地潮土施用小麦和玉米秸秆生物质炭对玉米养分吸收和根际土壤胞外酶活性的影响

  【目的】  生物质炭施用于农田土壤中能够改善土壤肥力，并提高作物生产力，而该效应受到土壤条件和生物质炭条件的限制。针对不同土壤条件探究适宜的生物质炭利用方式，对促进农业生产具有重要意义。  【方法】  采用盆栽试验，以壤质和粘质两种质地的潮土为研究对象，分别施用玉米秸秆炭(MBC)和小麦秸秆炭(WBC)两种生物质炭，并以不施用生物质炭的处理为对照(CK)。测定各处理玉米苗期生长、生理抗性和养分吸收差异，并分析各处理根际土壤理化性质和胞外酶等活性。  【结果】  1)与CK相比，壤质潮土中，WBC处理下玉米地上部生物量显著增加了43.7%，总根长显著增加34.3%，而MBC处理没有显著影响。粘质潮土中，WBC和MBC对玉米生物量和根系构型均影响较小。2) WBC和MBC在壤质和粘质潮土中显著降低了苗期玉米叶片中MDA含量，降低幅度在32.7%～55.3%，且两种生物质炭之间没有显著差异；粘质潮土中，MBC处理显著提高了玉米叶片超氧化物歧化酶(SOD)活性，壤质潮土中，WBC和MBC处理对SOD活性均没有显著影响。3)壤质潮土中，生物质炭对苗期玉米地上部氮含量没有显著影响，而对作物全磷和全钾含量有显著促进作用，WBC处理的地上部全磷和全钾含量分别比对照显著提高23.5%和28.7%，且显著高于MBC处理。在粘质潮土中，WBC和MBC处理对地上部全氮和全磷含量均没有显著影响，而MBC处理提高了全钾含量。4)在壤质和粘质潮土中施用生物质炭均改善了根际土壤理化性质。与对照相比，壤质潮土中MBC处理的土壤速效磷含量显著增加了25.4%；粘质潮土中WBC和MBC处理速效磷含量均显著增加了15.03%，并且显著提高了阳离子交换量(CEC)。生物质炭处理提高了根际土壤胞外酶活性，在粘质潮土中WBC和MBC处理的胞外酶活性没有显著差异，而在壤质潮土中WBC处理的酶活性高于MBC处理。  【结论】  施用生物质炭能够调控根际土壤酶活性，提高有效磷含量，改善玉米根系构型，提高苗期玉米养分吸收并增加生物量。生物质炭的施用效果在壤质潮土中比粘质潮土中更好，小麦秸秆炭效应优于玉米秸秆炭。

Effects of wheat and corn straw biochar application on nutrient uptake of maize and extracellular enzyme activities in the rhizosphere of different textural fluvo-aquic soils

  【Objectives】  The effects of biochar on enhancing crop productivity and soil fertility is limited by soil and biochar properties. In this study, we explored the suitable utilization mode of biochar according to different soil conditions.  【Methods】  A pot experiment was conducted in loam and clay fluvo-aquic soils. The soils were treated with wheat straw biochar (WBC) and maize straw biochar (MBC), and the same treatment without biochar was prepared as a control (CK). The physicochemical characteristics and extracellular enzyme activity of rhizosphere soil and maize growth, resistance, and nutrient absorption were examined.  【Results】  1) WBC enhanced maize seedling growth and improved root architecture in loam fluvo-aquic soil (P<0.05). Shoot biomass increased by 43.7%, and total root length increased by 34.3% in WBC under loam fluvo-aquic soil (P<0.05), compared with CK. In the clay fluvo-aquic soil, biochar treatment showed little effects on maize seedling biomass and root system architecture. Our results showed that biochar amendment could promote maize seedling growth in loam fluvo-aquic soil, and WBC was better than MBC. 2) Biochar soil amendment could improve maize resistance at the seedling stage. The two biochars decreased MDA content in maize leaf by 32.7%?55.3% in a similar manner. MBC increased the SOD activity in clay fluvo-aquic soil (P<0.05), while WBC had no effect. In contrast, SOD activity did not differ among the treatments in loam fluvo-aquic soil. 3) Biochar could promote the nutrient absorption of maize at the seedling stage. The two bioachar treatmens did not affect maize N content but increased P and K content in loam fluvo-aquic soil. Specifically, WBC increased P and K content by 23.5% and 28.7%. In clay fluvo-aquic soil, biochar showed no effects on maize N and P content, while MBC increased K content. 4) Biochar amendment improved soil fertility and increased extracellular enzyme activity. Compared with CK, MBC increased available phosphorus content by 25.4% in loam fluvo-aquic soil. Both MBC and WBC treatments inceased available phosphorus content by 15.03% in clay fluvo-aquic soil, and soil CEC was significantly increased (P<0.05). Biochar increased the activity of extracellular enzymes related to C, N, and P cycling. There was no significant difference in extracellular enzymes activity in clay fluvo-aquic soil (P>0.05). Conversely, WBC recorded higher extracellular enzymes activity than MBC in loam fluvo-aquic soil.  【Conclusions】  The application of biochar to fluvo-aquic soil could improve maize productivity at the seedling stage, increase maize root architecture, and regulate soil nutrient cycling in the rhizosphere. This effect was better in loam fluvo-aquic soil than in clay fluvo-aquic soil, and WBC had a higher effect than MBC.