关中平原冬小麦临界磷浓度稀释曲线的构建与磷营养诊断

  【目的】  基于关中平原冬小麦施磷量与小麦磷营养的关系，建立临界磷浓度稀释曲线，为当地冬小麦科学施磷提供理论依据。  【方法】  长期定位施磷田间试验始于2009年，供试小麦品种为‘西农979’。设置4个施磷水平(P₂O₅) 0、60、120、180 kg/hm2，分别记为P0、P60、P120和P180处理。于2018—2021年冬小麦拔节期、孕穗期、开花期、灌浆期和成熟期取样，分析冬小麦地上部生物量、植株磷浓度，记录小麦产量。利用2018—2020年冬小麦地上部生物量和植株磷含量建立临界磷浓度稀释模型，计算磷营养指数 (PNI)。依据2020—2021年冬小麦数据验证磷营养指数诊断的可靠性。  【结果】  1) 施用磷肥可显著增加冬小麦穗数和穗粒数，显著降低千粒重，2018—2021年3季冬小麦依次提高穗数50.7%～53.0%、23.1%～29.7%和17.5%～19.0%，穗粒数依次提高28.6%～34.2%、22.7%～24.1%和18.7%～19.6%，千粒重依次降低1.1%～2.9%、3.5%～7.0%和1.3%～4.9%，P60、P120和P180处理间穗数、穗粒数(2018—2019年除外)差异不显著。随着施磷量增加，冬小麦籽粒产量先持续增高而后降低，施磷处理下2018—2021年3季冬小麦依次增产104.3%～108.2%、39.8%～47.4%和27.6%～32.5%，在P120处理下产量达到最大值，2018—2021年3季依次为7100、6369和6714 kg/hm2。2) 冬小麦地上部生物量随生育进程的推进逐渐增加，地上部磷浓度随生育进程推进逐渐降低。同一取样时期，施磷量增加，地上部生物量和磷浓度也随之增加。据此，本研究2019—2020年建立的临界磷浓度稀释曲线模型为P_c=6.00DM–0.43，模型RMSE值为0.09，n-RMSE值为3.45%，表明模型模拟值的可靠性和稳定性达到要求。3) 随着施磷量增加，磷营养指数 (PNI) 增大，磷营养指数 (PNI) 在P120处理下最接近1。各施磷量处理下，冬小麦磷营养指数 (PNI) 随生育期的变化较小。  【结论】  依据不同施磷量下冬小麦地上部生物量和磷浓度，建立的临界磷浓度稀释曲线模型与磷营养指数 (PNI) 模型能够准确诊断关中平原冬小麦不同生育阶段的磷素盈亏状况，可用来指导关中平原冬小麦植株各生育期磷素含量评估和磷肥施用。

Construction of critical phosphorus concentration dilution curve and phosphorus nutrition diagnosis of winter wheat in Guanzhong plain

  【Objectives】  Based on the relationship between winter wheat phosphorus application rate and wheat phosphorus nutrition in Guanzhong Plain, we established a critical phosphorus concentration dilution curve to provide a theoretical basis for meeting the P needs of local winter wheat.  【Methods】  The long-term localization phosphorus field experiment was established in 2009, and the wheat variety was Xinong 979. The four phosphorus application treatments (P₂O₅) tested were 0, 60, 120, 180 kg/hm2, noted as P0, P60, P120 and P180, respectively. The above-ground plant samples were determined at the jointing, booting, flowering, filling, and maturity periods of the winter wheat from 2018 to 2021, and the above-ground biomass and plant phosphorus concentration were analyzed, the wheat yield was also evaluated. A critical phosphorus concentration dilution model was used to calculate the P nutrient index (PNI). The reliability of phospho-nutrition index was verified based on winter wheat data from 2020 to 2021.  【Results】  1) P fertilization significantly increased the panicle number in three seasons by 50.7%–53.0%, 23.1%–29.7%, and 17.5%–19.0%, increased the grain number per panicle by 28.6%–34.2%, 22.7%–24.1% and 18.7%–19.6%, but reduced 1000-grain weight by 1.1%–2.9%, 3.5%–7.0% and 1.3%–4.9%, respectively. The panicle number elicited by P120 and P180 treatments were similar. With the increase in P application rate, the grain yield increased first and then decreased, and the yield in the three seasons was increased by 104.3%–108.2%, 39.8%–47.4%, and 27.6%–32.5% on average, with the maximum yield of 7100 kg/hm2, 6369 kg/hm2, and 6714 kg/hm2 under the P120 treatment. 2) The aboveground biomass of winter wheat gradually increased with the progress in the growth process, and the P concentration in the upper aboveground part gradually decreased. Based on the aboveground biomass and P concentration of winter wheat in 2019—2020, a critical P concentration dilution curve model was established: P_c=6.00DM–0.43, with the RMSE of 0.09, and n-RMSE of 3.45%, indicating that the reliability and stability of the model simulation values meet the requirements. 3) The PNI of wheat was mainly affected by P application rate, not by growing stage. P120 treatment had the PNI closest to 1.  【Conclusions】  Based on above-ground biomass and P concentration of winter wheat under different P application rates, the critical phosphorus concentration dilution curve model and P nutrition index (PNI) model can ideally diagnose the status of phosphorus, balance in winter wheat in Guanzhong plain, and can be used as a tool for phosphorus content assessment and guidance of phosphorus fertilizer application.