Effect of biochar fertilizers on amino acid variability of Secale cereale and Lupinus angustifolius

Biochar (2019) 1:187–201 https://doi.org/10.1007/s42773-019-00012-7 ORIGINAL ARTICLE Effect of biochar fertilizers on amino acid variability of Secale cereale and Lupinus angustifolius Katja Wiedner1 · Corinna Schimpf1 · Steven Polifka1 · Bruno Glaser1 Received: 28 March 2019 / Accepted: 20 June 2019 / Published online: 15 July 2019 © Shenyang Agricultural University 2019 Abstract Little is known on the effects of biochar on N uptake and amino acid variability in crops such as winter rye and narrow-leafed lupine despite the fact that amino acids are important indicators, for food quality and plant stress. N uptake of both crops showed contrasting results when treated with different biochar fertilizers. Total amino acid contents referred to total nitrogen generally tend to decrease in rye grains in the presence of biochar; whereas lupine seeds were more or less unaffected by biochar combined with mineral fertilizer or compost. In lupine seeds, total amino acid contents significantly increased when biochar was mixed with digestate but decreased when mixed with fermented digestate. Lysine, one of the most limiting amino acids in cereals, reached the recommended value of 4 g kg−1 in rye grain for most biochar fertilizers. In lupine seeds, lysine decreased when biochar had been applied but were still in the recommended range when used as animal feed. Proline, an indicator for plant stress, significantly decreased (− 49%) in rye when 2 Mg biochar ha−1 was added in combination with mineral fertilizer. In contrast, proline increased when biochar was added to organic (digestate and compost) fertilizers (up to 43%). Further biochar research should focus much more on food quality, which is a key challenge for global food production. Keywords Food quality · Protein · Lupine · Winter rye · Yield 1 Introduction In search of solutions for sustainable agricultural practices, attention in recent years focused on biochar, a carbon-rich biomass carbonization product. Meanwhile, almost 6000 articles with biochar in the title are listed in the ISI Web of Science database especially dealing, with physical and chemical properties, and its effects on soil fertility and soil microbiology, its ability to sequester carbon in the long term or to increase crop yield, little is known about the interaction of biochar combined with mineral or organic fertilizers and its impact on amino acid composition in plants. Amino acids are on the one hand indicators for food/fodder quality but on the other hand crucial for plant metabolic processes (Foyer et al. 2003). Amino acids play an important role for plants when subjected to stress acting, e.g., as osmolyte, * Katja Wiedner 1 Soil Biogeochemistry, Institute of Agronomy and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Von‑Seckendorff‑Platz 3, 06120 Halle (Saale), Germany regulation of ion transport, modulating stomatal opening, and detoxification of heavy metals (Rai 2002). The content and composition of amino acids in plants are affected by environmental conditions (Nikiforova et al. 2006), and as mentioned above, the studies indicating the effects of biochar on plant biochemical and physiological activities are limited. Besides this, amino acids are important for human and animal diet. In the future, food systems need to be more efficient, and resilient which means using sustainable land with practices as well as producing food with high nutritional content. As summarized in several reviews and meta-analyses, biochar as soil conditioner showed contradictory results regarding nutrient availability, biochar stability, plant nutrition and yield (Sohi et al. 2009; Atkinson et al. 2010; Biederman and Harpole 2013). A biochar field experiment under realistic conditions performed by Glaser et al. (2015) also showed inconsistent results regarding the effects of different biochar fertilizer (digestate, fermented digestate, mineral fertilizer and compost) on soil properties and crop yield. The results from this experiment raised the question, whether and to what extent biochar fertilizers affect amino acid patterns and contents as well as N uptake into plant. 13 Vol.:(0123456789) 188 Biochar (2019) 1:187–201 In this study, winter rye (Secale cereale) and narrow-leafed lupine (Lupinus angustifolius) were investigated, because both crops are important in northern regions due to their low demands on soil quality and having a high frost tolerance. Indeed, rye plays only a minor role in global crop production, but in northern countries, rye is a suitable crop due to its robustness and its main cultivation area in Northern Europe. Rye grains contain ~ 54% carbohydrate, ~ 9% protein, ~ 13% fibres and ~ 2% fats and minerals. The high proportion of essential amino acids is especially valuable for human nutrition. In contrast to lupine, rye plays an almost negligible role as grain for animal feed. Lupine is traded as substitute for soy in the north or in other words as alternative protein source to soybeans growing readily on nutrient-poor sandy soils under Central European climatic conditions (Lucas et al. 2015). Due to their biological N 2 fixation capacity, lupine is an ideal plant for crop rotation, increasing yield and nutrient uptake of subsequent crops (Lizarazo et al. 2015). Therefore, lupine plays an important role for organic farming in Europe with regard to local and self-produced feed materials. Like other legumes, lupine is rich in protein, minerals, and dietary fibre, and thus a good supplement to animal feed. Narrow-leafed lupine seeds have a crude protein content of ~ 31%, which is only slightly lower than that of soybean (~ 35%). Besides protein, lupine also contains considerable amounts of nutrients, which depend (also like its biological N 2 fixation potential) on the plant varieties and on numerous (micro) climatic variables, soil properties and agronomic management factors (van Kessel and Hartley 2000; Beyer et al. 2015; Bartkiene et al. 2016). In this study, we aimed to evaluate the effect of different biochar fertilizers on amino acid variability and nitrogen uptake in winter rye grain and lupine seeds as indicator for nutritional quality. The study was guided by the following research questions: 1. Does the presence of biochar increase the yields of Secale cereale and Lupinus angustifolius? 2. Does biochar favor the nitrogen uptake of Secale cereale and Lupinus angustifolius independent of the fertilizer combined with biochar? 3. Is amino acid variability in Lupinus angustifolius seeds and Secale cereale grains influenced by the presence of biochar? 2 Materials and methods 2.1 Location and weather conditions during the experiment The field trial is located near Gorleben at 53°01′09.26″N and 11°29′50.04″E19 m above sea level in the Wendland region of Lower Saxony, Germany. The nutrient-poor sandy soil (Table 1) of the field was classified as Stagnic Cambisol resulting from Quaternary dynamics (Glaser et al. (...truncated)