Ecosystem Services Provided by Cover Crops and Biofumigation in Sunflower Cultivation

In south-western France, sunflowers are usually grown in short rotations and after a long fallow period during which soils are left bare. This practice can favour diseases, caused by soilborne fungi, such as sunflower verticillium wilt (SVW), as well as nitrate leaching, both of which can decrease yields. Growing cover crops during a fallow period is an agroecological practice that could provide ecosystem services and mitigate SVW. A Brassicaceae cover crop that causes biofumigation produces glucosinolates and liberate biocidal compounds that might regulate SVW biologically. Moreover, the green manure effect of the Fabaceae might increase soil mineral nitrogen (SMN). To go further, mixtures of Brassicaceae and Fabaceae might mutualise the benefits that each cover crop has in sole crops. A four-year field study in south-western France tested Brassicaceae (brown mustard, turnip rape and fodder radish) and Fabaceae (purple vetch) in sole crops or a mixture with two or three species during the fallow period, followed by biofumigation, and sunflower crop. The cover crops were characterised, SMN was measured, the SVW and yield were assessed and compared to those of the crop grown on soils left bare during the fallow period. Purple vetch as a sole crop cover crop significantly increased SMN before sunflower sowing but only in 2019. Fodder radish as a sole crop reduced SVW severity significantly, overall, 80 days after sowing, except in 2019, when weather conditions were unfavourable to biofumigation. Purple vetch as a sole crop also reduced significantly SVW severity in 2017 and 2020. Finally, sunflower yields after cover crops were higher than those after bare soils, only after purple vetch as a sole crop in 2020, with a mean increase of 0.77 t ha−1. Mixtures of Brassicaceae and Fabaceae sowed at these densities resulted in an intermediate SMN level between those in sole crops and the bare soil and they did not significantly decrease SVW or increase yields. Our results suggest that cover crops, especially fodder radish or purple vetch, and biofumigation can provide ecosystem services for sunflower, instead of leaving soils bare during the fallow period. However, the extent of ecosystem services is markedly affected by soil and climatic conditions as well as other management practices.

Energy balance and efficiency in crop rotation systems

The production system model that has been adopted in most Brazilian regions, the soybean/second corn crop succession, has led to problems in water and soil conservation and favorable conditions for diseases, pests, and weeds in the agricultural system and, consequently, increasing its energy use. Crop rotation is an alternative to this production model, directly interfering with the problematic aspects of the crop succession system and, consequently, its energy balance. Therefore, this study aimed to identify the crop rotation system with the best energy balance and efficiency. The data on the quantity of inputs (seeds, fertilizers, pesticides, and fuel), labor, and grain yield used in the study were collected from a crop rotation experiment conducted at the experimental station of the Rural Development Institute of Paraná - IAPAR-EMATER, Londrina, PR, Brazil, from 2014 to 2020. The experimental design consisted of randomized blocks, with six treatments and four replications. The treatments consisted of T1 (second corn crop/soybean), T2 (white oat/soybean, triticale/corn, and wheat/soybean), T3 (rye + black oat/soybean, black oat + fodder radish/corn, and congo grass/soybean), T4 (canola/corn, crambe/corn; canola/soybean); T5 (buckwheat-fodder radish/corn, bean/soybean, and buckwheat-white oat/ soybean), and T6 (wheat/corn, canola/corn + congo grass, and bean/soybean). The different crop rotations and the traditional second corn crop/soybean system provided positive energy balance and efficiency, that is, they produced more energy than they consumed. The canola/corn, crambe/corn, and canola/soybean rotation systems had the highest energy balance and efficiency, with values of 866,442.27 MJ ha−1 and 10.27, respectively, mainly due to corn cultivation in the summer, which resulted in a higher energy return than the other grain-producing crops.

WEEDS IN SOYBEAN CULTIVATION WITH DIFFERENT PREDECESSOR COVER CROPS

The competition between soybean and weeds affects crop development due to reduced resources such as water, light, and nutrients, leading to yield losses. Thus, the study aimed to evaluate quantitatively and qualitatively, through phytosociology and seed bank, the weed presence in a soybean cultivation area with different predecessor cover crops. The experiment was installed under no-till system conditions using a randomized block design with nine treatments and three replications. The treatments were composed of the following cover crops, sorghum (Sorghum bicolor), crotalaria (Crotalaria ochroleuca), millet (Pennisetum americanum), Urochloa ruziziensis, U. brizantha cv. Piatã, fodder radish (Raphanus sativus L.), U. brizantha cv. Xaraés, millet + fodder radish, and fallow. The soybean crop was established on the cover crops in the 2019/20 harvest. Soybean characteristics, the seed bank, and weed phytosociology were evaluated. The highest soybean yield was obtained with U. ruziziensis as predecessor cover crop, reaching 4530 kg ha-1. It was concluded that the following cover crops, sorghum, crotalaria, and millet, were the ones that most suppressed the soil weed seed bank. Contrarily, the fallow provided the greatest viable seed number. The weed species Eleusine indica, Digitaria insularis, and Cenchrus echinatus had higher phytosociological values in all treatments.

The Effects of Using Sulfur and Organic Bedding on the Content of Macro-and Micronutrients and Biologically Active Substances in Winter Garlic Bulbs

Sulfur (S) directly influences the proper development, yield, and biological value of Allium sativum. The sulfuric forms of S are easily leached from the soil due to poor sorption. In this context, we looked at to what extent application of S and biomass of catch crops (CCs) left until spring would cause an increase in the yield; we also looked at the macro- and micronutrient content of garlic plants. The experimental factors included applications of 0 and 20 kg ha−1 S to CCs consisting of Trifolium alexandrinum, Raphamus sativus var. oleiformis, Fagopyrum esculentum, Sinapis alba, and control. The bulbs contained more dry matter and macro- and micronutrients (N, P, K, S, Zn, and Fe) than those without S. Garlic plants cultivated with S accumulated more glutathione and total phenolic acids (TPA), and the extracts showed greater antioxidant activity (AA) than those cultivated without S. In 2019 and 2020, the cultivation of winter garlic with S, in combination with clover contributed to an increase in the content of dry matter, S, TPA, AA in bulbs. In the cultivation with fodder radish garlic plants accumulated more nitrogen (N), S, TPA, AA and glutathione in bulbs. In those cultivated with buckwheat, garlic contained more TPA, AA, glutathione, and with mustard more TPA and AA. However, further research is needed to select the species of CC and to determine the S dose to be applied in the effective biofortification of garlic in a sustainable agriculture system.