{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T04:47:57Z","timestamp":1785905277896,"version":"3.56.0"},"reference-count":59,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T00:00:00Z","timestamp":1785715200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["52269009"],"award-info":[{"award-number":["52269009"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["52069001"],"award-info":[{"award-number":["52069001"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["52469007"],"award-info":[{"award-number":["52469007"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"award":["52269009"],"award-info":[{"award-number":["52269009"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"award":["52069001"],"award-info":[{"award-number":["52069001"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"award":["52469007"],"award-info":[{"award-number":["52469007"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Key Research and Development Program of Gansu Province","award":["23YFFA0020"],"award-info":[{"award-number":["23YFFA0020"]}]},{"name":"Fifth Batch of \u201cFuxi Young Talents\u201d Program of Gansu Agricultural University","award":["Gaufx-05Y11"],"award-info":[{"award-number":["Gaufx-05Y11"]}]},{"name":"Young Mentor Support Fund of Gansu Agricultural University","award":["GAU-QDFC-2023-12"],"award-info":[{"award-number":["GAU-QDFC-2023-12"]}]},{"name":"Water Resources Science Experiment Research and Technology Promotion Project of Gansu Province","award":["GSAU-JSFW-2023-144"],"award-info":[{"award-number":["GSAU-JSFW-2023-144"]}]},{"name":"Water Resources Science Experiment Research and Technology Promotion Project of Gansu Province","award":["25GSLK038"],"award-info":[{"award-number":["25GSLK038"]}]},{"name":"Water Resources Science Experiment Research and Technology Promotion Project of Gansu Province","award":["26GSLK074"],"award-info":[{"award-number":["26GSLK074"]}]},{"name":"Water Resources Science Experiment Research and Technology Promotion Project of Gansu Province","award":["26GSLK087"],"award-info":[{"award-number":["26GSLK087"]}]},{"name":"Natural Science Foundation Special Project","award":["26TRRA444"],"award-info":[{"award-number":["26TRRA444"]}]},{"name":"Gansu Jingtai Goji Berry Science and Technology Backyard"},{"name":"Gansu Provincial Engineering Research Center for Pollution-free Cultivation of Goji Berry"},{"name":"Gansu Provincial Agricultural Smart Water-saving Technology Innovation Center"},{"name":"Research Center for Ecological Protection and Coordinated Agricultural Development in the Upper and Middle Reaches of the Yellow River"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Plants"],"abstract":"<jats:p>Water and nitrogen application rates directly affect crop yield formation and protein accumulation. Nitrogen metabolism, as a key physiological process linking water and nitrogen supply with crop growth, plays a critical role in regulating nitrogen uptake, transformation, and accumulation. However, the functional relationships among different nitrogen metabolism indicators in mediating the formation of high-quality and high-yield alfalfa under water\u2013nitrogen regulation remain unclear. In this study, alfalfa (Medicago sativa L.) was subjected to four nitrogen application levels [N0 (0 kg\u00b7hm\u22122), N1 (80 kg\u00b7hm\u22122), N2 (160 kg\u00b7hm\u22122), N3 (240 kg\u00b7hm\u22122)] and four irrigation gradients [severe deficit (W0, 45\u201360% \u03b8f), moderate deficit (W1, 55\u201370% \u03b8f), mild deficit (W2, 65\u201380% \u03b8f), and full irrigation (W3, 75\u201390% \u03b8f), where \u03b8f represents field capacity]. The relationships between water\u2013nitrogen regulation and alfalfa nitrogen metabolism and productive performance were analyzed. The results showed that (1) both irrigation amount and nitrogen application rate significantly affected the activities of leaf nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), and soluble protein (SP) content (p &lt; 0.05). Aboveground nitrogen content (TN) initially increased and then decreased with increasing irrigation and nitrogen application, reaching its maximum under W2N2, with leaves being the primary site of aboveground nitrogen accumulation. (2) Under W2N2, alfalfa yield and crude protein accumulation (CP-a) both reached their maximum values, averaging 10.22 t\u00b7ha\u22121 and 1187.10 kg\u00b7ha\u22121, respectively. (3) Structural equation modeling (SEM) indicated that water\u2013nitrogen regulation primarily influenced yield and CP-a formation through its effects on GS activity and TN. Based on these findings, a comprehensive evaluation model (GS\u2013TN\u2013Yield\u2013CP-a) was constructed, and the preliminary suitable water\u2013nitrogen regulation ranges for high-quality and high-yield alfalfa were identified as an irrigation amount of 69.4\u201385.9% \u03b8f and a nitrogen application rate of 102.6\u2013222.3 kg\u00b7hm\u22122. These results can provide a theoretical basis for high-quality and high-yield alfalfa management in arid and semi-arid regions, but further verification through field experiments is still required.<\/jats:p>","DOI":"10.3390\/plants15152380","type":"journal-article","created":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T14:16:27Z","timestamp":1785766587000},"page":"2380","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Effects of Water and Nitrogen Regulation on Alfalfa (Medicago sativa L.) Production Performance Through Optimization of Nitrogen Metabolism"],"prefix":"10.3390","volume":"15","author":[{"given":"Mingzhu","family":"Wang","sequence":"first","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hui","family":"Fan","sequence":"additional","affiliation":[{"name":"Hydrology Bureau of Haihe River Water Conservancy Commission, Tianjin 300170, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yubin","family":"Zhang","sequence":"additional","affiliation":[{"name":"Gansu Academy for Water Conservancy, Lanzhou 730000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3744-8146","authenticated-orcid":false,"given":"Minhua","family":"Yin","sequence":"additional","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanxia","family":"Kang","sequence":"additional","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guangping","family":"Qi","sequence":"additional","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Boda","family":"Li","sequence":"additional","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuqing","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Water Conservancy and Hydropower Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,3]]},"reference":[{"key":"ref_1","first-page":"24","article-title":"Response of a new alfalfa line to salt stress","volume":"35","author":"Ren","year":"2026","journal-title":"Acta Prataculturae Sin."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Kulkarni, K.P., Tayade, R., Asekova, S., Song, J.T., Grover, S.J., and Lee, J.D. 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