AUTHOR=Yang Yuanyu , Zhang Jianwei , Chang Xia , Chen Lunlun , Liu Yongmin , Xu Qingwei , Wang Mengjuan , Yu Haiyan , Huang Renmei , Zhang Jie , Hu Yingxiao , Hu Qijuan , Shi Xiaojun , Zhang Yuting 

TITLE=Green manure incorporation enhanced soil labile phosphorus and fruit tree growth

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1356224

DOI=10.3389/fpls.2024.1356224

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>The incorporation of green manures substantially enhances the conversion of external phosphorus (P) fertilizers and soil-reserved P into forms readily available to plants. The study aims to evaluate the influence of green manure additions on soil phosphorus dynamics and citrus growth, considering different green manure species and initial soil phosphorus levels. Additionally, the research seeks to elucidate the microbiological mechanisms underlying the observed effects.</p></sec><sec><title>Methods</title><p>A citrus pot experiment was conducted under both P-surplus (1.50 g·P·kg<sup>-1</sup>) and P-deficient (0.17 g·P·kg<sup>-1</sup>) soils with incorporating legume (Leg), non-legume (Non-Leg) or no green manure residues (CK), and <sup>18</sup>O-P labeled KH<sub>2</sub>PO<sub>4</sub> (0.5 g, containing 80‰ δ<sup>18</sup>O<sub>p</sub>) was additionally introduced to trace the turnover characteristics of chemical P fertilizer mediated by soil microorganisms.</p></sec><sec><title>Results and discussion</title><p>In P-surplus soil, compared with the CK treatment, the Leg treatment significantly increased soil H<sub>2</sub>O-P<sub>i</sub> (13.6%), NaHCO<sub>3</sub>-P<sub>o</sub> (8.9%), NaOH-P<sub>i</sub> (9.5%) and NaOH-P<sub>o</sub> (30.0%) content. It also promoted rapid turnover of P sources into H<sub>2</sub>O-P<sub>i</sub> and NaHCO<sub>3</sub>-P<sub>i</sub> pools by enhancing the <italic>phoC</italic> (576.6%) gene abundance. In contrast, the Non-Leg treatment significantly augmented soil H<sub>2</sub>O-P<sub>i</sub> (9.2%) and NaHCO<sub>3</sub>-P<sub>o</sub> (8.5%) content, facilitating the turnover of P sources into NaHCO<sub>3</sub>-P<sub>i</sub> pools. Under P-deficient soil conditions, compared with the CK treatment, the Leg treatment notably raised soil H<sub>2</sub>O-P<sub>i</sub> (150.0%), NaHCO<sub>3</sub>-P<sub>i</sub> (66.3%), NaHCO<sub>3</sub>-P<sub>o</sub> (34.8%) and NaOH-P<sub>i</sub> (59.0%) content, contributing to the transfer of P sources into NaHCO<sub>3</sub>-P<sub>i</sub> and NaOH-P<sub>i</sub> pools. This effect was achieved through elevated ALP (33.8%) and ACP (12.9%) activities and increased <italic>pqqC</italic> (48.1%), <italic>phoC</italic> (42.9%), <italic>phoD</italic> (21.7%), and <italic>bpp</italic> (27.4%) gene abundances. The Non-Leg treatment, on the other hand, led to significant increases in soil NaHCO<sub>3</sub>-P<sub>i</sub> (299.0%) and NaHCO<sub>3</sub>-P<sub>o</sub> (132.6%) content, thereby facilitating the turnover of P sources into NaHCO<sub>3</sub>-P<sub>i</sub> and NaOH-P<sub>i</sub> pools, except for the <italic>phoC</italic> gene abundance. Both Leg and Non-Leg treatments significantly improved citrus growth (7.3-20.0%) and P uptake (15.4-42.1%) in P-deficient soil but yielded no substantial effects in P-surplus soil. In summary, introducing green manure crops, particularly legume green manure, emerges as a valuable approach to enhance soil P availability and foster fruit tree growth in orchard production.</p></sec>