Root morphology, yield and must composition of grapevine subjected to application of urea methods and rates

Nitrogen (N) is often applied to soil surface during the grapevine cycle, increases N losses. One way to reduce N losses lies on its application method, however how N dose and application mode impact on grapevines remain poorly investigated. The aim of this study is to evaluate the root growth, as well as grape must yield and composition, in a sandy soil and subjected to different N application doses and modes under subtropical climate conditions. Grapevines were implanted in 2011 and, since 2014, they were subjected to surface (N-Surf), and fertigation (N-Fert) N application, at rates of 0, 40 and 100 kg N ha−1 year−1. Leaf N concentration, yield, must quality parameters and root system morphology were evaluated in the 2016/2017 and 2017/2018 seasons. The application of N in both rates (40 and 100 kg N ha−1 year−1), in the N-Surf and N-Fert methods, increased the surface area of root, number of living roots and root production. The application of N rates, in both N application modes, provided adequate N supply to the soil and increased root system development, which contributed to the increase of soil N uptake by plants, higher N concentration in leaves and greater grape yield. However, N supply decreased the quality of the must, as observed in decreased TSS and total anthocyanins values and in increased total titratable acidity values, which are not desirable for red wine making processes.

氮素（Nitrogen, N）常被施用于葡萄生育周期内的土壤表层，此举会加剧氮素流失。减少氮素流失的途径之一在于其施用方式，但目前关于氮肥施用量与施用模式如何影响葡萄植株的相关研究仍较为匮乏。本研究旨在探究亚热带气候条件下，砂质土壤中不同氮肥施用量与施用模式对葡萄根系生长、葡萄醪（grape must）产量及组分的影响。供试葡萄植株于2011年定植，自2014年起分别采用表层施氮（N-Surf）与滴灌施肥（N-Fert）两种方式施加氮肥，施用量设为0、40和100 kg N·ha⁻¹·a⁻¹。研究人员于2016/2017与2017/2018两个生长季，对植株叶片氮素浓度、葡萄产量、葡萄醪品质参数及根系形态进行了测定。无论是采用表层施氮还是滴灌施肥方式，施用量为40和100 kg N·ha⁻¹·a⁻¹的氮肥均能提升根系表面积、活根数量与根系生成量。两种施氮模式下，不同氮肥施用量均可为土壤提供充足的氮素供应，促进根系发育，进而提升植株对土壤氮素的吸收效率，提高叶片氮素浓度并增加葡萄产量。但施氮会降低葡萄醪的品质：具体表现为总可溶性固形物（Total Soluble Solids, TSS）与总花色苷含量下降，而总可滴定酸度升高，这对于红葡萄酒酿造工艺而言是不利的。