College of Resources and Environment, Southwest University, Beibei District, Chongqing 400715, China.
College of Resources and Environment, Southwest University, Beibei District, Chongqing 400715, China.
Ecotoxicol Environ Saf. 2023 Oct 1;264:115441. doi: 10.1016/j.ecoenv.2023.115441. Epub 2023 Sep 5.
Fertilization and cultivation managements exert significant effects on crop growth and soil-associated nutrients in croplands. However, there is a lack of knowledge regarding how these practices affect soil phosphorus-cycling enzymes and functional genes involved in regulating global P-cycling, especially under intense agricultural management practices in sloping croplands. A long-term field (15-year) trial was conducted in a 15° sloping field based on five treatments: no fertilizer amendments + downslope cultivation (CK); mixed treatment of mineral fertilizer and organic manure + downslope cultivation (T1); mineral fertilizer alone + downslope cultivation (T2); 1.5-fold mineral fertilizer + downslope cultivation (T3); and mineral fertilizer + contour cultivation (T4). Bulk and rhizosphere soil samples were collected after the maize crop was harvested to determine the P fraction, P-cycling enzymes, and phosphatase-encoding genes. Results indicated that fertilization management significantly increased the inorganic (Pi) and organic soil (Po) P fractions compared to CK, except for NaOH-extractable Po in T1 and T3 in bulk and rhizosphere soils, respectively. For the cultivation treatments, the content of Pi pools in the downslope cultivation of T1 and T3 was significantly larger than that in the contour cultivation of T4 in bulk and rhizosphere soils. However, the content of NaOH-extractable Po in T1 and T3 was lower compared to T4 in bulk soil and vice versa for the NaHCO-P and HCl-Po fractions in the rhizosphere. We also found that fertilization and cultivation managements significantly increased the activity of acid phosphatase (ACP), alkaline phosphatase (ALP), phytase, phosphodiesterases (PDE), and phoC and phoD gene abundance in bulk and rhizosphere soils, with a larger effect on the activity of ALP and the phosphatase encoding phoD gene, especially in T1 and T3 in the rhizosphere. Soil organic carbon (SOC) and microbial biomass C and P (MBC and MBP) were the main predictors for regulating P-cycling enzymes and phoC- and phoD gene abundance. A strong association of P-cycling enzymes, especially ALP and phytase, and the abundance of phoD genes with the P fraction indicated that the soil P cycle was mainly mediated by microbial-related processes. Together, our results demonstrated that an adequate amount of mineral fertilizer alone or combined with organic fertilizer plus downslope cultivation is more effective in promoting soil P availability by enhancing the activity of ALP, phytase, and phoD genes. This provides valuable information for sustaining soil microbial-regulated P management practices in similar agricultural lands worldwide.
施肥和培管措施对农田作物生长和土壤相关养分有显著影响。然而，我们对于这些措施如何影响土壤磷循环酶以及参与调控全球磷循环的功能基因知之甚少，特别是在坡度较大的农田中，这些措施在高强度农业管理实践下的影响。在一个基于 5 种处理的 15 年田间长期试验中，该试验在一个 15°的坡地上进行：不施肥+顺坡耕作（CK）；矿质肥和有机肥混合处理+顺坡耕作（T1）；仅矿质肥+顺坡耕作（T2）；1.5 倍矿质肥+顺坡耕作（T3）；矿质肥+等高耕作（T4）。在玉米作物收获后采集原状和根际土壤样本，以测定磷形态、磷循环酶和磷酸酶编码基因。结果表明，与 CK 相比，施肥管理显著增加了无机（Pi）和有机土壤（Po）磷形态，除了 T1 和 T3 的原状和根际土壤中 NaOH 可提取的 Po 分别在 T1 和 T3 中。对于耕作处理，T1 和 T3 的顺坡耕作中 Pi 库的含量显著大于 T4 的等高耕作中 Pi 库的含量，而原状土壤中 T1 和 T3 的 NaOH 可提取 Po 含量低于 T4，反之为根际土壤中 NaHCO3-P 和 HCl-Po 分。我们还发现，施肥和耕作管理显著增加了原状和根际土壤中酸性磷酸酶（ACP）、碱性磷酸酶（ALP）、植酸酶、磷酸二酯酶（PDE）和 phoC 和 phoD 基因丰度的活性，特别是在 T1 和 T3 的根际中，ALP 和编码 phoD 基因的磷酸酶活性的影响更大。土壤有机碳（SOC）和微生物生物量 C 和 P（MBC 和 MBP）是调节磷循环酶和 phoC 和 phoD 基因丰度的主要预测因子。磷循环酶，特别是 ALP 和植酸酶，以及 phoD 基因与磷形态之间的强烈关联表明，土壤磷循环主要由微生物相关过程介导。总之，我们的研究结果表明，单独或结合使用适量的矿质肥和有机肥加顺坡耕作，通过提高 ALP、植酸酶和 phoD 基因的活性，更有效地促进土壤磷的有效性。这为在全球类似农业土地上维持土壤微生物调控磷管理实践提供了有价值的信息。
