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Soybean is a thermophilic and photophilic plant very sensitive to weather course during the vegetation period. This trait limits soybean cultivation in higher latitude countries. This field study aimed to evaluate the effects of three sowing dates on the development, the duration of vegetative and generative stages, and the yield of two soybean cultivars (Lissabon and Merlin) under conditions in south-western Poland in the years 2016–2019. The sowing date determines the temperature and the day length available for soybean plants, influencing development and yield. Delaying the sowing date by 20 days in relation to the earliest (16–21.04) resulted in the shortening of the length of the vegetative development by 12 days and the shortening of the entire vegetation period by 14 days. The delayed sowing date (06–19.05) under the conditions of south-western Poland (Lower Silesia) contributed to a significant decrease in yield. Lissabon produced greater soybean yield than Merlin. Special attention should be paid to proper seed sowing dates in soybean agriculture practice. It is necessary to breed soybean genotypes adapted to day length and thermal conditions of the cultivation area to achieve the maximum seed yield.

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In 2015–2017, field experiments were conducted, in two facilities of the Wroclaw University of Environmental and Life Sciences: at the Research and Didactic Station in Psary (51°19′08” N, 17°03′37” E) and in the plots of the Department of Crop Production in Pawlowice (51°17′32” N, 17°11′72” E). The research aimed to evaluate fresh biomass yield and selected quality parameters of quinoa grown as a green leafy vegetable. The study was conducted on two soils: medium (clay soil texture) and light (sand soil texture), sowing quinoa in spring and summer periods. On both soils, quinoa was harvested 5 times at each sowing date. The yields of fresh plant biomass, basic morphological characteristics and certain quality traits were compared. All experimental factors had a significant effect on quinoa fresh biomass yield. On light soil, quinoa yielded 4 times lower than on medium soil, and its cultivation posed a high risk, especially at the summer sowing date. The experimental factors used had the greatest effect on macronutrient content. Growing quinoa on medium soil yielded biomass with higher K, Mg, Ca and N-NO3 concentration, while spring sown plants had higher K and N-NO3 concentration. Harvesting date had the greatest effect on the change in nutritional values. Potassium content decreased as the harvest date was delayed, and N-NO3 content decreased gradually until the fourth harvest date. The results showed that quinoa should be harvested as a green leafy vegetable when it reaches a height of 20–30 cm; biomass production is then at 500–1000 g per m2, potassium content is less than 10 g per 100 g dry matter and N-NO3 content is less than 100 mg 100−1 f.m.

Because of the different opinions regarding nitrogen (N) requirements for Miscanthus × giganteus biomass production, we conducted an experiment with a set dose of nitrogen. The objective of this study was to examine the effects of nitrogen fertilization on the biomass yield, water content, and morphological features of rhizomes and aboveground plant parts in various terms during a growing season over the course of three years (2014–2016) in Lower Silesia (Wroclaw, Poland). The nitrogen fertilization (dose 60 kg/ha and control) significantly affected the number of shoots (p = 0.0018), the water concentration of rhizomes (p = 0.0004) and stems (p = 0.0218), the dry matter yield of leaves (p = 0.0000), and the nitrogen uptake (p = 0.0000). Nitrogen fertilization significantly affected the nitrogen uptake in all plant parts (p = 0.0000). Although low levels of nitrogen appeared to be important in maintaining the maximum growth potentials of mature Miscanthus × giganteus, the small reductions in the above- and belowground biomass production are unlikely to outweigh the environmental costs of applying nitrogen. More studies should use the protocols for the above- and belowground yield determination described in this paper in order to create site- and year-specific fertilizer regimes that are optimized for quality and yield for autumn (green) and spring (delayed) harvests.

Guizotia abyssinica (Guizotia abyssinica (L.f.) Cass.) is regarded as a minor oilseed crop, which is important in terms of its nutritional value and potential uses. An important benefit of this crop is its cultivation for green matter and seed yield even under the difficult conditions of marginal cultivation. Guizotia abyssinica has not yet gained popularity in Europe. However, in a changing climate and taking into account its feeding value, it could gain in importance for ruminant nutrition in the near future. A field experiment was conducted in 2018 and 2019 in the west part of Poland on a farm in Opolskie voivodship (commune Prudnik). The objective of the field study was to assess the effect of three harvest dates on the yield and the chemical composition of fodder in a 90-day cultivation cycle in each year of the study. Stage of growth seems to be the most important factor affecting yield and the chemical composition of Guizotia abyssinica. In both years of the research, the green fodder yield reached the highest value after 90 days from sowing—32.5 and 36.9 t ha−1—while dry matter was 6.85 and 7.99 t ha−1, respectively. Chemical composition was also significantly dependent on harvesting date. Crude protein (in 2018 from 154.5 to 100.7 g kg−1 and in 2019 from 148.3 to 78.2 g kg−1) and crude ash (in 2018 from 165.8 to 98.7 and in 2019 from 155.2 to 89.9 g kg−1) content decreased with progressive harvest date while nitrogen-free extracts (in 2018 from 500.5 to 562.0 g kg−1 and in 2019 from 582.2 to 605.2 g kg−1) and gross energy increased (in 2018 from 19.4 to 21.17 MJ kg−1 and in 2019 from 18.63 to 19.73 MJ kg−1.). The most favorable date for harvesting green forage is 90 days after sowing, due to the significantly highest yield of fresh and dry matter of green forage and with potential as a forage for animals.

Previous research indicated the potential use of struvite (STR) as an alternative source of phosphorus (P) in crop production. A greenhouse experiment was conducted to evaluate the effect of STR and triple superphosphate (TSP) on the growth and chemical composition of butterhead lettuce grown on peat substrate over a three-month period (May–July). Both alternative (STR) and conventional (TSP) fertilizers were applied at three rates: (1) recommended rate based on the elemental content of substrate and crop nutritional need; (2) reduced rate (50% lower than recommended); and (3) increased rate (50% higher than recommended). Unfertilized (control) plants were also grown in the pot experiment. As expected, fertilizer application tended to increase the content of heavy metals in the substrate. Thus, an increase in Zn, Pb, and Cu content in peat substrate was found following STR amendments. However, compared with unfertilized plants, the applied rates of the STR and TSP fertilizers did not increase the content of Cd and Cu in the plant leaf, while Hg content was below the detection limit. In addition, Zn content in the plant leaf significantly decreased following STR and TSP applications. In comparison to unfertilized plants, both alternative and conventional fertilizers increased the content of P and nitrate nitrogen (N-NO3−) in the plant leaf while their effect on Mg content was negligible. The increased rate of STR was the best fertilizer treatment because it produced the largest number of leaves, which were also characterized by the highest P content. Our findings showed that STR was an effective source of P in butterhead lettuce cultivation without adverse effects on heavy metal accumulation.

The wastewater treatment process generates large amounts of P-rich organic waste (sewage sludge (SS)). The direct application of SS in agriculture, being controversial, is gradually being replaced by incineration, leading to the concentration of both P and heavy metals in the solid residual-sewage sludge ash (SSA). The novel closed-loop, cradle-to-cradle (C2C) approach leads to maintaining P production at current levels and counteracts its depletion in the future. The aim of this review is the presentation of the implementation of the C2C approach for P recovery. The paper focuses on steps that comprise P C2C, starting from the SS properties, being a derivative of wastewater type and treatment processes, to SS pre-treatment and finally leading to certified P-fertilizers production from SSA by application thermochemical or wet chemical extraction technologies. Examples of SSA treatment technologies and the final products are provided. It has been summarized that future research should focus on the production of SSA-based fertilizers aligning with the C2C concept and determining its effect on the various agriculture and horticulture crops.