ALBERT

Description: Agriculture, Vol. 8, Pages 43: Hungry Plants—A Short Treatise on How to Feed Crops under Stress Agriculture doi: 10.3390/agriculture8030043 Authors: Silvia Haneklaus Elke Bloem Ewald Schnug Fertilisation is as old as is the cultivation of crops. In the 19th century, plant nutrition became an area of research in the field of agricultural chemistry. Liebig’s “Law of the Minimum” (1855) is still the basis for plant nutrition. It states that the exploitation of the genetically fixed yield potential of crops is limited by that variable, which is insufficiently supplied to the greatest extent. With a view to abiotic and biotic stress factors, this postulation should be extended by the phrase “and/or impaired by the strongest stress factor”. Interactions between mineral elements and plant diseases are well known for essential macro- and micronutrients, and silicon. In comparison, the potential of fertilisation to alleviate abiotic stress has not been compiled in a user-orientated manner. It is the aim of this chapter to summarise the influence of nutrient deficiency in general, and the significance of sodium, potassium, and silicon, in particular, on resistance of crop plants to abiotic stress factors such as drought, salinity, and heavy metal stress. In addition, the significance of seed priming with various nutrients and water to provide tolerance against abiotic stress is discussed. Underlying physiological mechanisms will be elaborated, and information on fertiliser application rates from practical experiences provided.

Description: Antibiotics enter agro-ecosystems via the application of farmyard manure, sewage sludge, animal by-products, or digestates. There are many open questions regarding the behavior of such compounds in the soil like their adsorption, degradation, half-life, and their effects on soil organisms and plants. The impact of antibiotics on the development of antibiotic resistance genes in the environment is regarded as the most important effect that endangers the environment as well as human health. Nevertheless, direct plant toxicity, especially of different antibiotics and heavy metals at the same time, can be of importance as well. In the current study, commercially available phytotoxkits were tested with regard to the toxicity of single antibiotics and antibiotics in combination with the root growth of Sinapis alba L. Additionally, a pot trial was conducted to study the transfer of the observed phytotoxkits results in more complex systems. The phytotoxkits revealed direct toxicity of antibiotics on root development only at high concentrations. The highest toxicity was determined for sulfadiazine, followed by tetracycline and enrofloxacin, showing the least toxicity. When two antibiotics were tested at the same time in the phytotoxkit, synergistic effects were detected. The pot trial indicated lower effect concentrations for enrofloxacin than determined in the phytotoxkit and, therefore, to higher toxicity on plant growth.

Description: Glyphosate is one of the most widely used non-selective systemic herbicides, but nowadays its application is controversially discussed. Optical remote sensing techniques might provide a sufficient tool for monitoring glyphosate use. In order to investigate the potential of this technology, a laboratory experiment was set-up using pots with rolled grass sods. Glyphosate-treated plants were compared to drought-stressed and control plants. All pots were frequently measured using a field spectrometer and a hyperspectral-imaging camera. Plant samples were analysed for photosynthetic pigments, polyphenols and dry matter content. Eight selected vegetation indices were calculated from the spectral measurements. The results show that photosynthetic pigments were sensitive to differentiate between control and glyphosate treated plants already 2 days after application. From the vegetation indices, the normalized difference lignin index (NDLI) responded most sensitively followed by indices referring to photosynthetic pigments, namely, the carotenoid reflectance index (CRI-1) and the photochemical reflectance index (PRI). It can be concluded that spectral vegetation indices are, in principal, a suitable proxy to non-destructively monitor glyphosate application on agricultural fields. Further research is needed to verify its applicability under field conditions. An operational monitoring is, however, currently limited by the requirements for temporal and spectral resolution of the satellite sensors.

Description: The aim of this field experiment was to analyze the influence of different nitrogen and sulfur doses on yield as well as the content and uptake of iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) by spring rye grain. The study was conducted in south-eastern Poland (2009–2011) on Cambisols (WRB 2015), in conditions of low sulfur content in soil. The experiment included four doses of N fertilization (0, 30, 60 and 90 kg ha−1) and two doses of S supplementation (0 and 40 kg ha−1). The analysis showed that fertilization with N and S had a positive effect on the studied features of spring rye. The highest grain yields were found after use of 90 kg N ha−1. The grain of rye fertilized with these doses of N was characterized by the highest concentration and uptake of tested microelements. The supplementation of sulfur in a dose of 40 kg S ha−1 improved the nitrogen effect, because the rye grain yield and the content and uptake of micronutrients (except Mn) by rye grain dry mass increased. The highest yield of spring rye grain and accumulation of Mn and Zn and intake of Mn, Zn and Cu by grain dry mass (DM) were obtained in the vegetation season of 2011, which was characterized by an optimal rainfall distribution. The highest accumulation of Fe and Cu and intake of Fe were obtained in the vegetation season of 2009. Significant correlations were found also between grain yield and the content and uptake of all studied micronutrients. The supplementation of NPK fertilization with sulfur can be a good means of agronomic biofortification for spring rye in order to increase the content and uptake of Fe, Mn, Zn and Cu.