Grain production and optical characteristics in three wheat (Triticum aestivum L.) varieties under liming and nitrogen fertilization

Liming of acidic soils occupying 73 million hectares of agricultural land in the Russian Federation is a traditional technique that provides optimization of soil conditions and contributes to obtaining high and stable yields. The cultivation of crops with intensive technologies is accompanied by the export of calcium with a yield, washing out with atmospheric precipitation, etc., so it is necessary to replenish calcium, which is economically costly. Knowing the optimum dosages for each type of ameliorant is necessary to adjust its quantity which provides the maximum effect from the application. For the first time, effect of various doses of ameliorant (limestone meal-dolomite) was evaluated in situ by the optical characteristics of spring wheat ( Triticun aestivum L.) cultivars Leningradskaya 97, Krasnoufimskaya 100 and Trizo differing in grain productivity and responsiveness to nitrogen fertilizer application. Plants were grown in 5 litre containers with sod-podzolic soil, in natural light. The rates of applied ameliorant were 0 (control), 0.25, 0.50, 0.75 and 1.00 Hy (mmolc 100 g-1). Nitrogen (ammonium nitrate) was applied before seeding in two doses: optimal (1 g N) and deficit (0.15 g N) nutrition level in 5 kg of soil. The content of other mineral nutrients in the soil was similar in all cultivars of the experiment. Spectral characteristics of radiation reflected from leave surface (300-1000 nanometers) were registered by a spectrometer HR2000 («Ocean Optics», USA). After reflection spectra recording, the spectral reflection indexes closely related to chlorophyll content, the ratio between the amount of carotenoids and that of chlorophylls, the light dispersion caused by changes of inner leaf structure, the activity of the photochemical processes of photosynthesis, anthocyanins and flavonols content were calculated. The results indicate that wheat cultivars respond differently to ameliorant and its favourable effect on plants productivity is more expressed under nitrogen deficiency. In response to ameliorant application at the optimum level of nitrogen supply, grain yield of cv. Leningradskaya 97 has not changed. Grain production of cv. Triso was higher throughout the range of application doses. Range of a positive response to the impact of ameliorant of cv. Krasnoufimskaya 100 was narrower in comparison to cv. Trizo and shifted toward lower doses. Close correlation between the grain yield under different ameliorant doses and the content of chlorophyll in the leaves (chlorophyll index) for the Krasnoufimskaya 100 ( R2 = 0.87) and Trizo ( R 2 = 0.88) was found. Changes in the indices which characterize efficiency of light energy conversion in the photochemical processes of photosynthesis, allows us to suggest that the ameliorant introduction not only promotes nitrogen absorption but also affects the efficiency of light energy use through photosynthesis.