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Growers in the United States (US) southeast are often recommended to reduce nitrogen (N) fertilization after peanut (Arachis hypogaea L.) by cooperative Extension services. However, these guidelines are not supported by the scientific literature. An experiment was conducted to quantify N contributions from peanut residues to a subsequent carinata (Brassica carinata) crop. A 3 (history: cotton [Gossypium hirsutum L.], peanut, fallow) × 5 (N rates: 0, 34, 67, 101,134 kg N ha−1) factorial randomized complete block split‐plot design was conducted over four site‐years during the 2018–2019 and 2019–2020 seasons at Jay, FL, USA. Peanut and cotton were planted under strip tillage, whereas carinata was drilled into peanut and cotton residues and weed‐free fallow plots. Although peanut residues accumulated 54–78 kg N ha−1, inorganic N content behind former peanut plots at the 0–15 cm depths, ranged from 6 to 8 and 8 to 11 kg N ha−1 in 2018–2019 and 2019–2020 season, respectively. Cropping history differences for carinata normalized difference vegetation index (NDVI) were pronounced at lower N rates in one out of four site‐years during which NDVI behind former cotton plots was lower than former peanut and fallow plots. Carinata seed yield behind former peanut plots was similar to unfertilized fallow based on four site‐years of data. Nonlinear regression models predicted that N rates required to optimize carinata seed yield following peanut would exceed 134 kg N ha−1 thereby indicating negligible peanut N credits. These results support a growing body of literature that suggests minimal N credits after peanut under humid southeastern US conditions. Core Ideas: Early season carinata NDVI differences behind peanut, cotton, and fallow plots diminished later in the season.Carinata seed yield behind former peanut plots was similar to unfertilized fallow plots across all N rates.Peanut N credits to subsequent crops were not detected. [ABSTRACT FROM AUTHOR]

Brassica carinata A. Braun is a non‐edible, oilseed winter crop for biofuel production that can diversify crop rotations and improve integrated weed management. The research objective was to evaluate the influence of B. carinata on weed population dynamics in the southeastern United States cropping systems. B. carinata was grown after cotton (Gossypium hirsutum L.), peanut (Arachis hypogea L.), or a clean summer fallow, and winter weed pressure was modified with or without S‐metolachlor. The emergence of Lamium amplexicaule L. increased at least 40% after cotton or peanut in 2018–2019 and 50% after cotton in 2019–2020 compared to summer fallow. Stellaria media (L.) Vill. emergence was increased over threefold after peanut or cotton in 2019–2020. Senna obtusifolia (L.) H.S. Irwin & Barneby emergence after cotton was increased at least 43% during both experimental years, whereas Amaranthus hybridus L. emergence was increased over 50% after peanut in 2019–2020 compared to summer fallow. Even without S‐metolachlor, B. carinata reduced A. hybridus (>27%) and S. obtusifolia (>25%) emergence compared to weedy winter fallow. After B. carinata harvest, A. hybridus emergence was reduced >40% with or without S‐metolachlor compared to winter fallow in 2018–2019. Overall, B. carinata biomass was highest after peanut for both seasons. B. carinata seed yield did not differ among crop history treatments in the first season, whereas in 2019–2020, the yield was higher after peanut (2417 kg ha−1) or fallow (2520 kg ha−1) compared to cotton (1710 kg ha−1). Weed management treatments were not different for B. carinata biomass or yield in any year. The results indicate that B. carinata can enhance integrated weed management strategies at the rotational level for summer crops by reducing seed banks of summer weed species, in addition to its potential as a winter biofuel crop for the southeastern United States. [ABSTRACT FROM AUTHOR]

Row croppers in the Southeast United States (SE US) are interested in diversifying their cropping systems and increasing revenue by growing a winter cash crop between summer crops, especially cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.). Double-cropping carinata (Brassica carinata A. Braun) between summer crops has potential to boost grower revenue and increase land use efficiency in the region. Given that this winter crop is fairly new in the SE US, its successful establishment in the region depends on its rotational fit into current cropping systems. Since incorporating carinata into the existing cropping systems in the region could influence the productivity of those systems, it is crucial to determine what changes row croppers should expect. To resolve this, research was conducted to quantify the effects of summer cropping history on the performance of carinata as part of diversified crop rotations in the SE US. A randomized complete block design with eight replications was implemented in Jay, Florida, over three years. Summer cropping history treatments were peanut, cotton, and summer fallow. Data was collected on carinata aboveground biomass and stover [including carbon (C) and nitrogen (N)]; yield (including yield components); and seed chemical composition (glucosinolates concentration, protein and oil contents, and oil composition). Carinata biomass, biomass C and N, stover residue, stover residue C and N, and stover residue C:N ratio were not affected by summer cropping history across years. Likewise, yield and seed chemical composition were not affected by summer cropping history. In terms of combined productivity of summer crops and carinata, cotton-carinata was the most productive system while fallow-carinata was the least productive. Overall, results from this study show that the insensitivity of carinata yield or seed quality to previous summer crops allows for flexibility in integrating carinata into existing rotations in the SE US. This simplifies the agronomic management of carinata as a biofuel crop since growers can concentrate on meeting yield goals without the risk of affecting yield or seed quality with different summer cropping histories. • Carinata was evaluated for yield and seed quality following cotton, peanut, and fallow cropping histories. • Carinata can be grown after cotton or peanut without compromising yield or seed quality. • Carinata has potential to be a fallow replacement winter crop for producing jet fuel in the Southeast US. [ABSTRACT FROM AUTHOR]

• Peanut is said to provide N credits to future crops in the southeastern USA but evidence is lacking to support this claim. • We evaluated wheat performance following peanut, cotton, and fallow in a conservation tillage cropping system. • Peanut residues contained up to 93 kg N ha-1, but available N at wheat planting was usually not affected by cropping history. • Peanut did not provide detectible N credits to wheat, but there were cases of lower yield after cotton relative to peanut. Agricultural extension services in many peanut (Arachis hypogaea L.)-producing regions recommend that farmers reduce nitrogen (N) fertilization rates, or apply N credits, to crops planted after peanut but do not typically specify how peanut residue management or planting schedules of subsequent crops affect the magnitude of peanut N credits. The objective of this study was to quantify peanut N credits to winter wheat (Triticum aestivum L.) in a conservation tillage cropping system in different subtropical growing environments. A five site-year study was conducted in Florida, USA beginning in 2016. A split-plot experimental design was arranged in which summer crop [peanut, cotton (Gossypium hirsutum L.), and weed-free fallow] was the main plot factor, while N rate (0, 34, 67, and 101 kg N ha−1) to winter wheat was the split plot factor. Peanut and cotton were planted under strip-tillage, while winter wheat was drilled into peanut and cotton residues and weed-free fallow plots without tillage. Although peanut residues accumulated 54–93 kg N ha−1, plant available N at winter wheat planting in the 0–15 cm soil depth range of former peanut plots was only higher than in former cotton or fallow plots for one site-year. A previous peanut crop did not affect winter wheat grain yield, but there were cases of lower grain yield, grain N removal, and agronomic efficiency following cotton relative to peanut depending on site. Nonlinear regression procedures predicted that N rates required to optimize grain yields following peanut would exceed 94 kg N ha−1, further indicating the absence of detectible peanut N credits in this study. These results suggest that assuming peanut provides N credits to subsequent crops in the southeastern USA is not justified and, if assumed, will reduce the productivity of subsequent crops. [ABSTRACT FROM AUTHOR]

• Performance of 11 Brassica carinata genotypes was evaluated for agronomically important traits. • Seasonal variation in environmental conditions, such as precipitation and temperature influenced agronomic performance. • Significant correlations were observed between seed and oil yield; bolting and flowering; bolting and maturity. • Principal component analysis clustered genotypes with high oil content, erucic acid content and protein content together. Brassica carinata A. Braun, grown as a winter crop on underutilized agricultural land in the southeast United States (SE US), may provide a new rotation alternative and augment income for producers. Widespread adoption of Brassica carinata as a winter crop in the SE US requires varieties with cold tolerance, acceptable and stable seed yield, oil content, protein content so that the crop will be complementary with the normal cultivation of summer crops such as cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean (Glycine max L. Merr), sorghum (Sorghum bicolor L. Moench) and peanut (Arachis hypogaea L.). The objective of this study was to evaluate the performance of 11 Brassica carinata genotypes for agronomically important traits including seed yield, oil and protein content, oil quality, days to bolting, flowering and maturity at three locations during two growing seasons (2015–2017) as a winter crop in the SE US. Interactions between genotype and environment played a crucial role in overall agronomic performance. This study provides key information on the effect of environmental conditions, such as precipitation and temperature on the agronomic performance of carinata along with generation of information related to region-specific requirements for the crop in the SE US. Days to maturity ranged from 154 to 165 days. The average yield of the 11 genotypes tested ranged from 2814 kg/ha to 3401 kg/ha, which were improved from earlier studies, demonstrating gain due to regional selection and breeding efforts. Total oil content ranged from 42.0 % to 52.4 %, while the erucic acid (C22:1) content ranged from 40.7 % to 42.9 % on a whole seed basis. Based on these results, specific genotypes with consistently high seed yield, oil, erucic acid and protein content with shorter life cycle irrespective of location or year were identified. Brassica carinata has potential as a viable bioenergy winter crop to be integrated into the cropping systems in the SE US and other regions of the world. [ABSTRACT FROM AUTHOR]