Robélio Leandro Marchão

Using cover crops (CCs) following annual crops, together with sustainable nitrogen (N) management, significantly enhances soil carbon (C) storage. However, carbon accumulation in tropical soils is strongly influenced by the respective crop sequences. This study evaluated soil C stocks and fractions in a system incorporating maize–soybean rotation and successive CCs. A randomized block design with split plots was implemented, where main plots consisted of different CCs and the subplots of treatments with and without N fertilization of maize. Chemical fractions of soil organic matter (SOM) were analyzed at depths from 0 to 40 cm, and C stocks down to 100 cm. The SOM fractions responded to N topdressing of maize, varying with soil depth. Soil C stocks during the maize phase were significantly higher than during soybean cultivation (p < 0.05), likely reflecting greater residue inputs from species with elevated C:N ratios. Legume crops following maize intensified C accumulation, emphasizing the importance of N inputs for soil C dynamics. Soil C losses were lowest in the treatments with Raphanus sativus without and Crotalaria juncea with N fertilization. These findings highlight the relevance of combining CCs and N management to optimize C sequestration in tropical agroecosystems.

Coffee intercropped with Urochloa decumbens modifies nutrient uptake, and consequently the yield and quality of coffee, by the greater release of nutrients and efficient nutrient cycling. There is little information about the increasing nutrient content in Arabica coffee plants intercropped with Urochloa decumbens. The objective of this study was to evaluate the effect of Urochloa decumbens intercropped with two coffee cultivars (Coffea arabica L.) on the levels of macro- and micronutrients and coffee crop yield. The experiment was conducted at Embrapa Cerrados, Planaltina-DF, and was arranged in a completely randomized block design with three replications, in a factorial design. The first factor consists of two management systems: with (WB) and without (NB) Urochloa decumbens intercropped; the second factor is composed of Arabica coffee cultivars ‘IPR-103’ and ‘IPR-99’. There was no significant difference in yield of the coffee cultivars with and without Urochloa decumbens intercropped between the rows. The treatment with ‘IPR-99’ coffee cultivar intercropped with Urochloa decumbens achieved 400 kg ha⁻¹ (8 bags) more than the other treatments. The presence of Urochloa decumbens increased leaf nutrient contents of the macronutrients Ca and Mg and micronutrients Mn and Fe. Thus, the Arabica coffee–Urochloa decumbens intercropping system is an efficiency management strategy which improves nutrient content for the main crop with consequent yield gains.

Bioinputs are natural products applied to crops that contribute to more sustainable agriculture by boosting yields and reducing environmental impacts. In Brazil, the use of bioinputs such as Bradyrhizobium in soybean has been consolidated, but the expansion of on-farm bioinput production is currently initiating a new revolution. Furthermore, applications of bioinputs to cash crops in Brazil have shed light on the great potential of such growth-promoting microorganisms (GMPs) to improve nutrient uptake and increase productivity. This study explores the effect of the complementary inoculation with growth-promoting bacteria of post-emergence soybean, previously inoculated with Bradyrhizobium spp. Five treatments with growth-promoting bacteria were evaluated: T1—Control (no inoculation); T2—Azospirillum brasilense; T3—Pseudomonas fluorescens and Azospirillum brasilense; T4—Priestia aryabhattai, Bacillus haynesii, and Bacillus circulans; and T5—Priestia megaterium and Bacillus subtilis. In comparison with the control, all treatments with growth-promoting bacteria of the genera Azospirillum, Pseudomonas, Priestia, and Bacillus, applied after soybean emergence, induced 4–7% higher grain yields. Co-inoculation with Priestia megaterium and Bacillus subtilis (treatment T5) resulted in a higher 1000-grain weight, while Priestia aryabhattai, Bacillus haynesii, and Bacillus circulans (treatment T4) increased the number of pods and shoot dry weight. Our conclusion is that bioinputs increase soybean productivity and make agriculture more sustainable and efficient.

The objective of this work was to evaluate changes in soil carbon contents and stocks in a ten-year long experiment under no-tillage, with the transition from corn to soybean, with cover crops and spontaneous vegetation in succession. The experimental design was a randomized complete block with three replicates, using ten different off-season covers: pigeon pea (Cajanus cajan), Brazilian jackbean (Canavalia brasiliensis), sunn hemp (Crotalaria juncea), black velvet bean (Mucuna aterrima), pearl millet (Pennisetum glaucum), radish (Raphanus sativus), sorghum (Sorghum bicolor), wheat (Triticum aestivum), ruzigrass (Urochloa ruziziensis), and spontaneous vegetation. Soil samples were collected in 2013, 2018, and 2024 at the depths of 0–10, 10–20, 20–30, 30–40, 40–60, 60–80, and 80–100 cm. Soil carbon stocks increased from 2013 to 2018, but declined between 2018 and 2024 after the introduction of soybean in 2021, except in treatments with sorghum and wheat. Between 2013 and 2024, soil carbon contents varied according to depth and type of cover crop. The corn-soybean rotation under no-tillage, with cover crops in succession, influences soil carbon dynamics. Sorghum shows the highest carbon accumulation between 2013 and 2024.

Bioinputs are natural products applied to crops that contribute to a more sustainable agriculture by boosting yields and reducing environmental impacts. This study explores the effect of complementary inoculation with growth-promoting bacteria on soybean development and yield. Five treatments with growth-promoting bacteria were evaluated: T1 - Control (no inoculation), T2 - Azospirillum brasilense strains CNPSo 2083 and CNPSo 2084, T3 - Pseudomonas fluorescens strain CNPSo 2719; Azospirillum brasilense strains CNPSo 2083 and CNPSo 2084, T4 - Priestia aryabhattai strain CBMAI 1120; Bacillus haynesii strain CCT 7926; Bacillus circulans strain CCT 0026 and T5 - Priestia megaterium strain BRM 119; Bacillus subtilis strain BRM 2084. In comparison with the control, all treatments with growth-promoting bacteria of the genera Azospirillum, Pseudomonas, Priestia and Bacillus, applied after soybean emergence, induced higher grain yield. Co-inoculation with Priestia megaterium and Bacillus subtilis (treatment T5) resulted in a higher 1000-grain weight, while Priestia aryabhattai, Bacillus haynesii and Bacillus circulans (treatment T4) increased the number of pods and shoot dry weight.

This study aimed to analyze the carbon (C) stock and stabilization of soil organic matter in particulate- and mineral-associated fractions across different land use systems after 32 years of experimentation in the Brazilian Cerrado. The experiment was established in 1991 and was performed in Planaltina-DF. The treatments evaluated included continuous pasture with monoculture grasses; integrated crop–livestock systems under no tillage; continuous cropping under no tillage; minimum tillage; and the preservation of the native Cerrado biome in its original condition. Soil sampling was performed to a depth of 30 cm. Carbon and nitrogen (N) stocks were quantified for the years 2001, 2009, 2013, and 2023, with soil organic matter fractionation performed on samples from 2023. Land use change resulted in significant losses of soil C and N in areas managed with conventional soil preparation practices. Systems that promote plant diversity, such as integrated crop–livestock systems, enhanced soil C and N stocks (72.8 and 5.5 Mg ha⁻¹, respectively) and increased both particulate organic matter and mineral-associated fractions, most of which were in more stabilized forms. Integrated crop–livestock systems are management practices that offer an effective alternative to present methods in terms of combating climate change and supporting ecosystem sustainability.

Cover crops in no-tillage systems may alter soil mineral N and influence the N fertilizer use efficiency (NFUE) of subsequent maize. The hypothesis of this work is that no-tillage systems with cover crops affect nitrate, ammonium and maize NFUE in the Brazilian Cerrado. The objective was to evaluate the cover crop mineralization effect on soil N mineral and maize NFUE in a no-tillage system, with and without N topdressing. The experiment was arranged in a randomized block split-plot design. The plots were represented by cover crops (Cajanus cajan, Crotalaria juncea, Raphanus sativus and Mucuna aterrima). The subplots consisted of the application (WN) or non-application (NN) of N topdressing to maize. The soil was sampled in six layers (up to 60 cm) at the end (April) and at the beginning of the rainy season (November). NH₄⁺ was lower for all cover crops and WN and NN management in April. NO₃⁻ differed between seasons and cover crops in WN and NN. The lignin concentration and N uptake of M. aterrima were the highest compared to other species. The highest NFUE was on R. sativus, showing higher fertilizer dependency. In a no-tillage system with cover crops, the N topdressing fertilization needs to be improved, considering mineralization.

The change in land use in the Brazilian Cerrado modifies the dynamics of soil organic matter (SOM) and, consequently, carbon (C) stocks and their fractions and soil enzyme activities. This study evaluated the effect of brachiaria (Brachiaria decumbens Stapf.) intercropped with Arabica coffee (Coffea arabica L.) on the stock and fractions of soil carbon and enzyme activities. The experiment was arranged in a completely randomized block design with three replications and treatments in a factorial design. The first factor consisted of coffee with or without intercropped brachiaria, the second of Arabica coffee cultivars (‘I.P.R.103’ and ‘I.P.R.99’) and the third factor of the point of soil sampling (under the canopy (UC) and in inter-rows (I)). Soil was sampled in layers of 0–10, 10–20, 20–30, 30–40, 40–60 and 60–80 cm. Soil from the 0–10 cm layer was also used to analyze enzymatic activity. Significant effects of coffee intercropped with brachiaria were confirmed for particulate organic carbon (POC), with highest contents in the 0–10 and 20–30 cm layers (9.62 and 6.48 g kg⁻¹, respectively), and for soil enzymes (280.83 and 180.3 μg p-nitrophenol g⁻¹ for arylsulfatase and β-glucosidase, respectively).

Edaphoclimatic conditions influence nitrous oxide (N₂O) emissions from agricultural systems where soil biochemical properties play a key role. This study addressed cumulative N₂O emissions and their relations with soil biochemical properties in a long-term experiment (26 years) with integrated crop–livestock farming systems fertilized with two P and K rates. The farming systems consisted of continuous crops fertilized with half of the recommended P and K rates (CCF1), continuous crops at the recommended P and K rates (CCF2), an integrated crop–livestock system with half of the recommended P and K rates (ICLF1), and an integrated crop–livestock at the recommended P and K rates (ICLF2). The ICLF2 may have promoted the greatest entry of carbon into the soil and positively influenced the soil’s biochemical properties. Total carbon (TC) was highest in ICLF2 in both growing seasons. The particulate and mineral-associated fractions in 2016 and 2017, respectively, and the microbial biomass fraction in the two growing seasons were also very high. Acid phosphatase and arylsulfatase in ICLF1 and ICLF2 were highest in 2016. The soil properties correlated with cumulative N₂O emissions were TC, total nitrogen (TN), particulate nitrogen (PN), available nitrogen (AN), mineral-associated organic carbon (MAC), and microbial biomass carbon (MBC). The results indicated that ICLF2 induces an accumulation of more stable organic matter (OM) fractions that are unavailable to the microbiota in the short term and result in lower N₂O emissions.