Synthesis of chlorophylls in chickpea plants under the action of mineral fertilizers and inoculants

Abstract

During 2016–2018 we studied the effect of different doses of mineral fertilizers, methods of their application, pre-sowing inoculation of seeds on the content of chickpea chlorophyll. The place of research is Odessa region, dry zone of the Black Sea steppe. Soil – southern low-humus heavy loam chernozem on forest deposits; availability of available forms of phosphorus and potassium – medium, nitrate nitrogen – low. Chickpea variety Memory, predecessor – winter wheat. Two-factor experiment: factor A – fertilizer system: P30K30 was applied for sowing cultivation, in other variants phosphorus-potassium fertilizers were supplemented with nitrogen at a dose of 30 and 60 kg / ha at the beginning of branching and flowering phases, there are variants with full mineral N30-60P30K30 and mono fertilizers N30-60; factor B – presowing seed treatment: without treatment, BTU-inoculant, rhizobophyte, rhizohumin. Chickpea leaves were selected from the upper part of the main stem by phases of growth; hoods were prepared in 100% acetone; measurements were performed by spectrophotometry: chlorophyll a – wavelength 662 nm, chlorophyll b – 644 nm; the concentration of pigments was determined by the formulas of D. Wettstein. Statistical processing of the results was performed according to generally accepted methods using the standard package of the program “Statistica-6”. The years of research differed greatly in weather conditions: the amount of precipitation during the period of active vegetation of chickpeas (from April to the first decade of August) was: 2016 – 245.3 mm, 2017 – 238.0 mm and 2018 – 66.0 mm. Chickpea vegetation during 2018 took place in conditions of soil drought. The hydrothermal coefficient averaged 0.26 during the growing season with fluctuations from 0.01 to 0.56 and was determined by the lack of precipitation because the average monthly air temperatures only in April and May were higher than in other years, and from June to August lower than 2016 by 1, 4-0.8 and 1.3o C, compared to 2017 – by 1.0-1.2 and 0.3o C. Stocks of productive moisture in a meter layer of soil in the period from the beginning of filling to the full maturity of chickpea grain in 2018 fluctuated from 30.2 mm to 0.0 mm; 2017 – from 56.7 mm to 33.8 mm and in 2016 – from 110.2 to 64.5 mm. According to the results of research, the following has been established: 1) the pool of chlorophyll varies according to the phases of development, fertilizer options and pre-sowing seed treatment options; the maximum content of green pigments was in the phase of flowering and the beginning of filling and was equal to 2.51-2.69 mg / g of raw material in the options of combined action of inoculants and fertilizers (N30-60P30K30 and N30-60) against 1.87-1.83 mg / g – control without fertilizers and without inoculation of seeds; the difference between the doses of nitrogen fertilizers is not mathematically significant; 2) the ability of inoculants to increase the content of chlorophyll in chickpea leaves was determined by the background of fertilizer: their maximum relative efficiency was observed in the unfertilized version and when applying phosphorus-potassium fertilizers (P30K30); in the flowering phase inoculants are located in the next row rhizohumin> rhizobophyte> BTU, and when ripe – BTU> rhizohumin> rhizobophyte; 3) under conditions of soil drought, the synthesis of chlorophyll decreases, especially the α fraction and the α / b ratio ranged from 2.03 to 1.54 against 3.89… 2.73 under optimal conditions; 4) the ratio between the fractions of chlorophyll tended to decrease according to the stages of development of chickpea plants and bacterization options in the transition from phosphorus-potassium fertilizer and complete to pure nitrogen due to increasing the share of chlorophyll b in the amount of chlorophyll from 1.5% to 3.5%; 5) there is a direct correlation between the concentration of chlorophyll in chickpea leaves in the flowering phase and the level of yield: for the pair crop – chlorophyll α the correlation coefficient was 0.78 – 0.64, and for chlorophyll b – 0.28 – 0.40; according to research years, a relatively closer relationship between chlorophyll b and chickpea grain yield was observed in less favorable weather conditions in 2018 (16.0 percent of the impact against 1.0-7.8% in other years), and chlorophyll α – in more favorable 2016 (60.8% vs. 32.5-41.0%).