Search

Cajanus cajan and Canavalia ensiformis are commonly used as cover crops due to their high biomass production, in addition they are also applied in recovery strategies for degraded areas. The objective of this study is to compare the tolerance, accumulation and translocation of Mn in the tissues of C. cajan and C. ensiformis, based on biomass production and the effects on the photosynthetic apparatus between species. The experiment was carried out in Red Latosol, contaminated with MnCl2 in the following concentrations: 0 (control), 80, 100, 120, 140 and 160 mg kg−1. Mn doses resulted in differentiated absorption, translocation and accumulation in plant organs, generating changes in the photosynthetic apparatus, reduction in dry mass and growth, and variations in tolerance and translocation levels between species. According to the results obtained, both species proved to be tolerant Mn and can be used in manganese management systems, they're able to accumulate Mn in tissues, and not only maintain but also improve biomass production at intermediate doses, C. cajan indicates to be a better option for phytostabilization of Mn, on the other hand C. ensiformis, indicates to be a better option for phytoextraction of Mn in soils with contents up to 160 mg kg−1. [ABSTRACT FROM AUTHOR]

Introduction and aims: In the context of increasing population and decreasing soil fertility, food security is one of humanity's greatest challenges. Large amounts of waste, such as sewage sludge, are produced annually, with their final disposal causing environmental pollution and hazards to human health. Sludge has high amounts of nitrogen (N), and, when safely recycled by applying it into the soil as composted sewage sludge (CSS), its residual effect may provide gradual N release to crops. A field study was conducted in the Brazilian Cerrado. The aims were to investigate the residual effect of successive applications of CSS as a source of N in the common bean (Phaseolus vulgaris L. cv. BRS Estilo)-palisade grass (Urochloa brizantha (A.Rich.) R.D. Webster)-soybean (Glycine max L.) rotation under notillage. Additionally, N cycling was monitored through changes in N metabolism; the efficiency of biological N2 fixation (BNF) and its implications for plant nutrition, development, and productivity, was also assessed. Methods: The experiment consisted of a randomized complete block design comparing four CSS rates (10, 15, 20, and 25 Mg ha-1, wet basis) to a control treatment (without adding mineral or organic fertilizer) over two crop years. Multiple plant and soil analyses (plant development and crop yield, Falker chlorophyll index (FCI), enzymatic, biochemical, 15N natural abundance, was evaluated, root and shoot N accumulation, etc.) were evaluated. Results and discussion: Results showed that CSS: i) maintained adequate N levels for all crops, increasing their productivity; ii) promoted efficient BNF, due to the stability of ureide metabolism in plants and increased protein content; iii) increased the nitrate content and the nitrate reductase activity in soybean; iv) affected urease activity and ammonium content due to changes in the plant's urea metabolism; v) increased N accumulation in the aerial part of palisade grass. Composted sewage sludge can be used as an alternative source to meet crops' N requirements, promoting productivity gains and N cycling through forage and improving N metabolism. [ABSTRACT FROM AUTHOR]