平衡施肥与秸秆覆盖对紫色土坡耕地养分及其化学计量的影响

为探究长期平衡施肥和秸秆覆盖对紫色土坡耕地土壤养分及其化学计量比的影响，以垫江县长期农田氮磷流失监测点为研究样地，设置3个处理：常规模式（CK）、平衡施肥模式（M1）和平衡施肥+秸秆覆盖模式（M2），每个处理各设3个重复，共建立9个小区（长7 m×宽3 m），并于2018、2019和2020年采集土样，研究不同处理下碳（C）、氮（N）、磷（P）和钾（K）含量及其化学计量变化特征.结果表明，2018年不同处理之间K含量差异显著，大小顺序为：CK>M2>M1；2019年不同处理之间硝态氮（NO₃^--N）、铵态氮（NH₄⁺-N）含量差异显著，表现为：M1>M2>CK；其他养分含量在同一年份不同处理之间差异均不显著.不同年份间各处理的土壤C和N含量差异不显著.2018年各处理中K含量均显著高于其他年份，其中，2018年的CK、M1和M2分别比2019年和2020年高78.26%和98.79%，19.13%和35.4%，54.49%和41.76%.P含量在CK和M2处理中均随着年份增大而减小，且2018年分别比2019年高20.29%和10.67%，比2020年高39.68%和17.33%.各处理不同年份间速效钾（AK）含量无显著差异，而NO₃^--N和NH₄⁺-N和速效磷（AP）含量差异显著，且均在2020年最高.土壤C ：P、C ：K、N ：P、N ：K和P ：K在不同年份间都表现出显著差异（P<0.05）.土壤C ：K、N ：K和AN ：AP分别于2018年和2019年在不同施肥模式间差异显著（P<0.05）.土壤C与N及P与K之间呈显著的线性正相关；土壤C ：K与C ：P、N ：K、N ：P和P ：K之间，N ：K与C ：P、P ：K和N ：P之间，N ：P与C ：P之间都呈显著的线性正相关；土壤P与C ：K和N ：K之间呈显著的线性负相关.土壤NO₃^--N与NH₄⁺-N、AN ：AP和AN ：AK之间，NH₄⁺-N与AN ：AP和AN ：AK之间，AP与AK和AP ：AK之间，AN ：AP与AN ：AK之间都呈极显著正相关.研究发现平衡施肥+秸秆覆盖是紫色土坡耕地较为适宜的管理模式.

Effects of Balanced Fertilization and Straw Mulching on Soil Nutrients and Stoichiometry in Purple Soil Slope

To explore the effects of long-term balanced fertilization and straw mulching on soil nutrients and stoichiometric ratios in purple soil sloping cropland, nine plots (length 7 m×width 3 m) were established in Dianjiang County as the research sample area of long-term farmland nitrogen and phosphorus loss monitoring. The following three treatments were set up:conventional mode (CK), balanced fertilization mode (M1), and balanced fertilization+straw mulching mode (M2), with three replications for each treatment to compare the contents of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) and their stoichiometric changes under different treatments from 2018 to 2020. The results showed:K contents showed significant differences among the three treatments in 2018, in the order of CK>M2>M1. NO₃^--N and NH₄⁺-N contents showed significant differences among the three treatments in 2019, both in the order of M1>M2>CK. Other nutrient contents showed no significant difference among different treatments each year. Soil C and N contents showed non-significant differences among different years. The total K contents of CK, M1, and M2 in 2018 were significantly higher than that in other years and were 78.26% and 98.79%, 19.13% and 35.4%, and 54.49% and 41.76% higher than that in 2019 and 2020, respectively. The total P content in the CK and M2 treatments decreased with years, and that of CK and M2 in 2018 was 20.29% and 10.67% and 39.68% and 17.33% higher than that in 2019 and 2020, respectively. The available potassium (AK) content of the three treatments showed non-significant differences among different years, whereas the contents of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and available phosphorus (AP) showed significant differences among the different treatments, with all being the highest in 2020. Soil C:P, C:K, N:P, N:K, and P:K ratios of each treatment showed significant differences among different years (P<0.05). Soil C:K, N:K, and AN:AP ratios all showed significant differences among different fertilization modes in 2018 and 2019, respectively (P<0.05). There was a significantly linearly positive relationship between soil C and N concentration and soil P and K concentration. There were very significant linear positive correlations between soil C:K and C:P, N:K, N:P, and P:K; N:K with C:P, P:K, and N:P; and N:P with C:P, N:P, and C:P. Soil P concentration was highly significantly linearly negatively correlated with C:K and N:K ratios. There were significant positive correlations between soil NO₃^--N, NH₄⁺-N, AN:AP, and AN:AK; NH₄⁺-N, AN:AP, and AN:AK; and AN:AP and AN:AK. The results suggested that balanced fertilization and straw mulching was a more suitable management mode for purple soil sloping cropland.