秸秆还田与水氮管理对水稻氮素利用及土壤理化性质的影响

在川西平原稻油轮作典型的砂质壤土区,设置不同秸秆还田方式(堆腐还田和直接还田)、灌溉方式(淹灌和有氧灌溉)和施氮水平(0、75、150、225 kg/hm2)的3因素裂区试验,分析秸秆还田与水氮管理对水稻氮素利用特征与土壤理化性质的影响.结果表明:秸秆还田与水氮管理对主要生育时期水稻氮素积累、结实期(抽穗和成熟期)氮素转运与利用、稻谷产量及成熟期稻田耕层(0～20 cm)土壤脲酶活性、铵态氮和硝态氮质量分数均存在显著或极显著的互作效应;秸秆堆腐还田对水稻氮素利用和产量及土壤理化性质的调控作用显著高于秸秆直接还田的,同一水氮管理下,成熟期植株和籽粒氮积累量分别提高了9.7％～32.9％和7.5％～45.3％,增产7.3％～18.5％,各生育期的平均土壤脲酶活性提高4.8％～9.7％;同一秸秆还田和施氮量处理下,相比于淹灌处理,有氧灌溉能不同程度的提高产量和氮肥表观利用率,并能提高多数处理的氮肥农学利用率、土壤铵态氮和硝态氮质量分数及脲酶活性;同一秸秆还田和灌溉方式,随着氮肥用量的增加,水稻氮肥表观利用率、农学利用率、产量、各器官(除2017年成熟期的穗外)和植株的氮素积累量及抽穗至成熟期茎鞘的氮素转运量、转运率、贡献率、土壤脲酶活性和硝态氮质量分数均先增加,施氮量为150 kg/hm2时最高,继续增加施氮量,这些指标反而降低.本研究条件下,油菜秸秆堆腐还田和有氧灌溉与配施150 kg/hm2氮肥的综合管理模式可有效增强结实期土壤耕层脲酶活性,提高植株氮素积累量、结实期茎鞘的氮素转运量和转运率,从而促进水稻产量及氮肥利用率的同步提高.

Effects of straw returning and water-nitrogen management on nitrogen utilization of rice and soil physicochemical properties

This study aimed to investigate the effects of straw returning and water-nitrogen management on nitrogen utilization of rice and soil physicochemical properties. Three factors split plot experiment was set up in the typical sandy loam area of rice-rape rotation in the Western Sichuan Plain: the main plot were two straw returning ways(composted straw and direct straw returning); the split plot were two ways of irrigation(flooded irrigation and aerobic irrigation); and the split-split plot were four N application rates(0, 75, 150, 225 kg/hm2). The results showed that straw returning and water and N management had significant interaction on N accumulation in rice at main growth stage, N translocation and utilization at filling stage(heading and maturity stage), rice yield and urease activity, mass fractions of ammonium and nitrate N of surface soil(0-20 cm) at maturity stage. The effects of composted straw returning on N utilization, yield of rice and soil physicochemical properties were significantly higher than those of direct straw returning. Under the same water-nitrogen management, compared with direct straw returning treatments, the N accumulation of plants and grains increased by 9.7%-32.9% and 7.5%-45.3%, respectively, the yields of rice increased by 7.3%-18.5%, and the average soil urease activities increased by 4.8%-9.7% of each growth period in composted straw returning treatments. Under the same straw returning and N application rate treatments, aerobic irrigation could increase the yields and N apparent use efficiency to different degrees, and increase the N agronomic use efficiency, soil ammonium and nitrate N mass fractions and urease activities of most treatments compared with flooded irrigation treatments. Within the same straw returning and irrigation methods, with the increase of N application rates, the N apparent and agronomic use efficiencies, yield, N accumulations of each organ(except for mature spike in 2017) and plant of rice, and the rice stem- sheath N translocation amount and efficiency, contribution rate, soil urease activity and nitrate N mass fraction from heading to maturation stages of rice increased first, these indexes were the highest when the N application rate was 150 kg/hm2, and then these indexes decreased over the N application rate increase. Under the conditions of this study, the combined management mode of composted rape straw returning, aerobic irrigation and combined application of 150 kg/hm2 N fertilizer could effectively enhance soil urease activity, N accumulation and N translocation amount and efficiency of stem-sheath during filling stage, which promoted the simultaneous improvement of high yield and N use efficiency.