Residual biomass quality index: a tool for conservation agriculture Cidimar Cassol, Paulo Cesar Conceição, Caroline Amadori, Maiara Karini Haskel, Leandro Alves de Freitas, et al. Revista Brasileira De Ciencia do Solo, 2023 One of the pillars of a no-tillage system is the addition of adequate amounts of residue to keep the soil continuously covered. Cover crops are a tool for supplying the demand for the permanence of residues on the soil surface and releasing nutrients to the soil. However, there is no index that relates these two factors and can reconcile the maximum permanence of crop residues in the soil with the maximum N supply via N mineralization of such residues. This study aimed to assess the effect of different cover crops on the decomposition rate of residues and N release, using the residual biomass quality index (RBQI) to evaluate cover crop systems. The study was conducted in a long-term experiment in a Latossolo Vermelho (Ferralsol, Oxisol) under no-tillage in the two agricultural years 2017/18 and 2018/19. The experiment was in a split-plot factorial scheme with eight winter cover crops and three N rates in randomized blocks with three replications. The cover crop systems were black oat (O), common vetch (V), forage radish (R), white lupine, rye, annual ryegrass, oat + vetch (O+V), and oat + vetch + radish (O+V+R). The N rates applied to the corn in succession were 0, 90, and 180 kg ha-1. The decomposition rate, remaining dry mass (RDM) on the soil surface, N release rate, and N accumulated release (NAR) were assessed using litterbags. Considering NAR and RDM evaluated for up to 105 days, the N release index (NRI) and remaining dry mass index (RDMI) were determined, and the residual biomass quality index (RBQI) was obtained using the product of these variables. The consortia O+V+R and O+V resulted in a decomposition rate and N release rate closer to the rates observed for oats and rye. The NAR was similar to that observed for Fabaceae species, and the RDM was similar or superior to that found for black oat. With these characteristics, the systems in the O+V+R and O+V consortia presented the highest values of RBQI, ranging from 0.61 to 0.90, indicating that RBQI is a potential indicator for choosing cover crop systems that promote greater sustainability of the no-tillage system. The use of N fertilizer in corn did not change the rates of decomposition and N release from the residues of cover crops.
Cover crops biomass yield grown as a 2nd summer crop in relation to sowing periods Karine Fuschter Oligini, Vanderson Vieira Batista, Carlos André Barhy, Paulo César Conceição, Laércio Ricardo Sartor, et al. Australian Journal of Crop Science, 2022 The aim of this study was to evaluate cover crop precocity and biomass yield growth as a 2nd summer crop after soybean at different sowing periods (January 2nd; February 2nd and March 2nd at 2019 and January 27th and March 3rd at 2020). Experiment was laid out as a randomized block design in a 3x3 factorial for each sowing period, in the 2019 and 2020 off-seasons, being factor A represented by the cover crops (Urochloa brizantha cultivar Xaraés, Crotalaria juncea cultivar IAC-KR-1 and Pennisetum glaucum cultivar ANm 38,) and factor B by the evaluation periods along cover crops development cycle. There was an interaction between cover crops and evaluation period for plant height and dry matter yield for both years. C. juncea and P. glaucum showed faster growth, regardless of the evaluation period and sowing periods, compared to U. brizantha in both years. Cover crop biomass yield reduced as sowing period is delayed from January to March to an extend that P. glaucum yield dropped from 14.6 to 4.2 t DM ha-1 at 2019 and from 14.4 to 6.9 t DM ha-1 at 2020 as a result shorter photoperiod and lower temperature. The same was noticed to U. brizantha and C. juncea which showed yields of 11.676 and 8.800 and 2.220 and 2.555 kg ha-1 at April 29th of 2019 and 12.507 and 7.812 and 3.041 and 2.346 kg DM ha-1 at June 18th 2020 respectively for January and March sowing periods. U. brizantha and C. juncea are more viable 90 days, while P. glaucum showed the fastest dry matter accumulation rate. All species are viable due to the benefits they provide to the productive system, which becomes more diversified and therefore more sustainable
