Effect of nitrogen fertilization management on mineral nitrogen content in soil and winter wheat productivity

I. Skudra¹ and A. Ruza²

¹Latvian Rural Advisory and Training centre, Street Rigas 34, LV3018 Ozolnieki region, Ozolnieki parish, Ozolnieki, Latvia
²Institute of Agrobiotechnology, Latvia University of Life Sciences and Technologies, Street Liela 2, LV3001 Jelgava, Latvia
E-mail: ilze.skudra@llkc.lv; antons.ruza@llu.lv

Abstract:

In recent years farmers must use integrated crop growing principles. One of the most important principle is to balance usage of mineral elements in crop cultivation, especially nitrogen management. Excessive and unbalanced usage of nitrogen fertilizer reduces nitrogen use efficiency and increases nitrate leaching in surface and groundwater. The dynamics of nitrogen forms in soil at different depths and different plant growth stages are studied to increase the productivity of winter wheat, promoting nitrogen uptake in plants and reducing nitrogen leaching during the vegetation period. Field experiments were carried out at the Research and Training Farm Vecauce of the Latvia University of Life Science and Technologies from 2012 till 2015. Researched factors were nitrogen (N) fertilizer rate: 0 – control, 85, 153, 187, and N rate determined by chlorophylmeter (Yara N-tester) 180 (2012/2013), 150 (2013/2014), 205 (2014/2015) N kg ha^-1, nitrogen and sulphur (S) fertilizer rate – N175+S21 kg ha^-1, and conditions of the growing seasons: 2012/2013, 2013/2014 and 2014/2015. The content of nitrate (NO₃–N) nitrogen and ammonium (NH₄–N) nitrogen was determined in the soil layers 0–20 cm, 20–40 cm and 40–60 cm at the growth stages (GS) 30–32, 49–51, 69 and 90–92. All trial years the amount of nitrate nitrogen and ammonium nitrogen in soil decreased during vegetation, but increased with increasing fertilization dose. Nitrate nitrogen content was significantly influenced by year in 0–40 cm soil layer (P < 0.01) and by nitrogen fertilizer in the 20–40 cm soil layer. Ammonium nitrogen content had significant influence only on nitrogen fertilizer at 20–40 cm soil layer (P < 0.05). Average grain yields did not show significant correlation with the nitrate nitrogen and ammonium nitrogen in different soil layers and plant growth stages, except nitrate nitrogen content in soil layer 40–60 cm at GS 30–32 and ammonium nitrogen content in soil layer 40–60 cm at GS 69 and GS 90–92.

Key words:

ammonium nitrogen, fertilizer, nitrate nitrogen, wheat

Chemical composition, nitrate reductase activity and plastid pigments content in lucerne under the influence of ammonium and nitrate form mineral nitrogen

V. Vasileva and A. Ilieva

Institute of Forage Crops, 89 Gen. “Vladimir Vazov” Str., Pleven 5800, Bulgaria, E-mail: viliana.vasileva@gmail.com

Abstract:

A pot trial was carried out at the Institute of Forage Crops, town of Pleven, Bulgaria (2003–04). Whereas ammonium and nitrate forms of mineral nitrogen are assimilated for the plants, the influence of these two forms of mineral nitrogen on the chemical composition, nitrate reductase activity and plastid pigments content of lucerne in conditions of optimum moisture and water deficiency stress was tested. Urea as a source of ammonium nitrogen and potassium nitrate as a source of nitrate nitrogen were used. Rates of 70, 140 and 210 mg N kg-1soil were applied. It was found that mineral nitrogen in ammonium form, applied at the doses of 140 and 210 mg N kg-1 soil at optimum moisture increased crude protein content by 5–13%, and in the nitrate form at the same doses, by 3–7%. Crude protein content under water deficiency stress increased by 4–21% for ammonium, and by 3–12% for the nitrate form of mineral nitrogen. When the plants were supplied insufficiently with nitrogen, water deficiency stress more strongly deteriorated the chemical composition of lucerne, crude protein decreased by 6% and crude fiber increased by 10%. The application of mineral nitrogen under optimum moisture decreased calcium and phosphorus content, and the decrease was bigger for the nitrate form (up to 10% for calcium, and 23% for phosphorus). Under water deficiency stress the content of calcium and phosphorus decreased, but there were no differences for two forms of mineral nitrogen. At the optimum moisture and water deficiency stress, there was a similar tendency to reduce nitrate reductase activity in leaves, when applied mineral nitrogen at a dose of 70 mg N kg-1 soil in both forms, and to increase at the doses of 140 and 210 mg N kg-1 soil. The total content of plastid pigments increased as compared to unfertilized control, when mineral nitrogen was applied in both forms.

Key words: