The yield and quality (volume weight, 1000 kernel weight, protein content, falling number, gluten content, gluten index, gluten content in dry matter) of winter wheat was studied in variety 'Portal'. The wheat was part of the five-year crop rotation experiment where red clover (Trifolium pratense L.), winter wheat (Triticum aestivum L.), peas (Pisum sativum L.), potato (Solanum tuberosum L.) and barley (Hordeum vulgare L.) were following each other. There were two production variants which followed the crop rotation. In one variant mineral fertilizers and pesticides were used, and the other variant was conversion to organic without any synthetic agrochemicals. In mineral fertilizing variant, on the background of P25 and K95 kg haE-1 the N amount varied from 0 to 150 kg haE-1 and herbicide Mustang (preparation norm 0.5 L haE-1, active substance florasulam, 6.25 g LE-1; 2.4-D, 300 g LE-1), insecticide Fastac 50 (preparation norm 0.2 L haE-1, active substance 50 g LE-1 alphacypermethrin) fungicide Falcon EC 460 (preparation norm 0.4 L haE-1, active substances 167 g tebuconazole, 250 g spiroxamine, 43 g triadimenol) and growth regulator Moddus (preparation norm 0.4 L haE-1, active substance 250 g LE-1 trinexapac-ethyl) were used. In conversion to organic the winter wheat grains which followed the red clovers after effect had higher volume weight, 1000 kernel weight and gluten index compared to the variants where mineral fertilizers were used. The yield, protein content, falling number and gluten content in dry matter increased with increase of the amount of mineral N. The wet gluten content was significantly higher compared to the other variants where the N amount was 50 kg haE-1.

Wheat (Triticum aestivum) is one of the main crops grown in Latvia. Nitrogen fertilizer is one of the most important factors affecting the acquired yield and its quality. The aim of this paper is to describe the nitrogen fertilization impact on winter wheat yield and yield components under two soil tillage systems and after two forecrops. Field trials were carried out at Research and Study farm ‘Peterlauki’ of Latvia University of Agriculture (56° 30.658°C N and 23° 41.580°C E) in 2014/2015 and 2015/2016. Researched factors were (1) crop rotation (continuous wheat and wheat/oilseed rape (Brassica napus ssp. oleifera), (2) soil tillage (traditional soil tillage with mould-board ploughing at a depth of 22 – 24 cm and reduced soil tillage with disc harrowing at a depth below 10 cm), and (3) nitrogen fertilizer rate (N0 or control, N60, N90, N120(90+30), N150(90+60), N180(90+60+30), N210(90+70+50), and N240(120+60+60). Results showed that the nitrogen fertilization significantly increased winter wheat grain yield after both forecrops and in both soil tillage variants. Grain yield significantly increased until the nitrogen fertilizer rate N180. Nitrogen fertilizer significantly affected all tested yield components. Values of yield components increased enhancing N-rate of N150 – N180. The forecrop had a significant impact on wheat yield and 1000 grain weight (both increased when wheat was sown after oilseed rape). Yield and grain number per ear were significantly higher when conventional tillage was used, but number of ears per square m – when the reduced tillage was used.

Wheat (Triticum) grain is generally used for food due to its grain quality. The two-factorial trial was conducted in the Research and Study farm ‘Pēterlauki’, Latvia, with an aim of finding out the soil tillage and crop diversification in rotation effect on winter wheat grain yield and quality. Two soil tillage systems (traditional and reduced) and three crop rotation schemes with different winter wheat (Triticum aestivum) fore-crops (wheat, oilseed rape (Brassica napus ssp. oleifera), faba bean (Vicia faba)) were used. The trial started in 2009. For this paper data from 2016/2017 and 2017/2018 growing seasons was used. Yields harvested in 2017 were significantly (p is less than 0.001) higher than those in 2018 (on average 7.17 t haE−1 in 2017, 6.18 t haE−1 in 2018). The highest yield (8.06 t haE−1) was gained in the variant where the fore-crop in 2017 had been faba bean. Crop rotation, including only repeated wheat sowings in both years, showed the lowest yield (on average 5.81 t ha E−1). Crop rotation with oilseed rape and wheat showed a significant wheat yield increase in the following two-year period in comparison to to repeated wheat sowings. A year as a factor had a significant (p is less than 0.05) impact on crude protein content (%), Zeleny index, volume weight (g LE−1) and 1000 grain weight (g). Both, volume weight (g LE−1) and 1000 grain weight, were influenced (p is less than 0.05) by the crop rotation and forecrop. Zeleny index depended on all researched factors. Crude protein content was influenced by soil tillage method (p is less than 0.0016) and fore-crop (p=0.0052). Hagberg falling number was not influenced by any of the investigated factors.