Vandecasteele Bart, Van Waes Chris
Plant Sciences Unit, Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Melle, Belgium.
Front Plant Sci. 2023 Aug 21;14:1210791. doi: 10.3389/fpls.2023.1210791. eCollection 2023.
In closed-loop soilless cultivation, the main nutrient sinks are nutrients retained either by the crop or in spent growing media. Measurement of nutrients in spent growing media and in the aboveground vegetative plant biomass at crop termination can be a tool for assessing and optimizing nutrient efficiency. The first aim of this study was to test the potential of near-infrared reflectance spectroscopy (NIRS) to forecast the various nutrient contents in strawberry leaves, which would then allow for assessment of crop nutrient status and total nutrient uptake by strawberry plants. The second aim was to test NIRS as a high throughput technique for assessing the N, K, Ca, Mg and organic matter (OM) content and the pH, EC and C:N and C:P ratios for a dataset of composts, plant fibers and spent growing media. The NIRS prediction model for fast screening of the total nutrient contents in spent growing media was compared with a single extraction method.
A database with 369 dried and ground strawberry leaf samples with known contents of N, P, K, Ca, and Mg were scanned using NIRS. The database covered a range of leaf contents of 6-35 g N/kg dry matter (DM), 0.7-6.3 g P/kg DM and 2-29 g K/kg DM. A dataset of 458 samples of different types of materials used in growing media was validated with a dataset of 109 samples.
Validation for the strawberry leaves indicated potential for this application, with R values of 0.90 or higher for N, K and Ca, and R values higher than 0.85 for P and Mg. Validation for the dataset of composts, plant fibers and spent growing media also indicated the potential for this application, with R values of 0.90 or higher for organic matter, and with R values of 0.85 or higher for total Ca, pH and C:N. A first test indicated potential for the calibration based on fresh samples of compost, plant fiber as well as spent growing media or dried (not ground) samples.
Use of NIRS on fresh samples would eliminate the need for drying and grinding the samples and would reduce screening time. The ammonium acetate extraction is a reliable alternative to NIRS for fast screening of the total P, K, Ca, and Mg contents in composts, plant fibers and spent growing media.
在闭环无土栽培中，主要的养分汇是作物保留的养分或用过的生长介质中保留的养分。在作物收获期测量用过的生长介质和地上营养植物生物量中的养分，可作为评估和优化养分效率的一种手段。本研究的首要目标是测试近红外反射光谱法（NIRS）预测草莓叶片中各种养分含量的潜力，进而评估草莓植株的作物养分状况和总养分吸收量。第二个目标是测试NIRS作为一种高通量技术，用于评估堆肥、植物纤维和用过的生长介质数据集中的氮、钾、钙、镁和有机质（OM）含量以及pH值、电导率（EC）、碳氮比和碳磷比。将用于快速筛选用过的生长介质中总养分含量的NIRS预测模型与单一提取方法进行了比较。
使用NIRS扫描了一个包含369个干燥研磨后的草莓叶片样本的数据库，这些样本的氮、磷、钾、钙和镁含量已知。该数据库涵盖的叶片含量范围为：氮6 - 35克/千克干物质（DM）、磷0.7 - 6.3克/千克DM、钾2 - 29克/千克DM。用109个样本的数据集对458个不同类型的用于生长介质的材料样本的数据集进行了验证。
对草莓叶片的验证表明了该应用的潜力，氮、钾和钙的R值为0.90或更高，磷和镁的R值高于0.85。对堆肥、植物纤维和用过的生长介质数据集的验证也表明了该应用的潜力，有机质的R值为0.90或更高，总钙、pH值和碳氮比的R值为0.85或更高。首次测试表明，基于堆肥、植物纤维以及用过的生长介质的新鲜样本或干燥（未研磨）样本进行校准具有潜力。
对新鲜样本使用NIRS将无需对样本进行干燥和研磨，并将减少筛选时间。对于快速筛选堆肥、植物纤维和用过的生长介质中的总磷、钾、钙和镁含量，醋酸铵提取法是NIRS的可靠替代方法。
