Les alpages sont des espaces utilisés par la majorité des exploitations d’élevage de montagne et de Provence, qui y envoient tout ou partie de leurs troupeaux durant la saison estivale. Ce sont des milieux très riches sur le plan environnemental, mais aussi très fragiles et gérés exclusivement par le pâturage des troupeaux, constituant de ce fait des espaces particuliers dans la problématique de l’adaptation au changement climatique pour les systèmes d’élevage provençaux et de montagne. Or le constat est fait que les approches de diagnostic d’alpage et les références utilisées au plan pastoral présentent des lacunes pour appréhender la gestion dynamique des alpages : vision statique des végétations d’alpage et des pratiques, prise en compte des aléas et de la variabilité interannuelle souvent réduite à un coefficient forfaitaire de sécurité... et pas de prise en considération des interactions entre alpage et exploitations utilisatrices. Afin de renouveler ces cadres d’analyse, notre travail de thèse propose une modélisation conceptuelle du fonctionnement du système « alpage-exploitations », intégrant les plans biophysique et de la gestion. La construction du modèle s’appuie sur la combinaison de travaux en écologie et en agronomie « système », et de dires d’expert (modélisation participative). Le modèle est mis à l’épreuve sur une diversité de cas, issus du réseau Alpages Sentinelles dans le massif Alpin. Une analyse de la vulnérabilité des systèmes à la recrudescence des aléas climatiques est effectuée en étudiant leur exposition aux aléas puis leur sensibilité ; afin d’intégrer la dynamique de long terme du changement climatique dans la gestion des alpages, une analyse mobilisant les théories de la résilience socio-écologique est proposée en complément. / Alpine pastures, or mountain summer pastures can be defined as permanent grasslands used in summer by mountain and surrounding plains farmers (especially Provence in the French Alps). They are rich but fragile ecosystems, managed exclusively through the grazing of herds. Therefore adaptation to climate change is very specific on these spaces. Pastoral diagnosis methods and technical references are insufficient to analyse dynamic management of summer mountain pastures: static vision of vegetation and practices, climatic hazards considered only through a security coefficient, and no consideration for interactions between summer pastures and farms. In order to renew these analytical frameworks, our PhD thesis proposes a conceptual model of how the system “mountain summer pastures-farm” works, both in biophysical terms and in terms of management. The building of this model relies both on researches in ecology and agronomy, and on participatory modelling. We evaluate the model through an analysis of the vulnerability to climatic hazards of a diversified sample of systems. In order to take into account long term dynamics of climate change, we also mobilise the theories of social-ecological resilience.

During spring kikuyu-ryegrass pasture has a low dry matter (DM) content (10-12%), is highly digestible and has high levels of soluble carbohydrates. Low rumen pH values have been recorded for cows grazing these pastures even when supplemented with low levels of concentrate. The rumen environment and extent of rumination may therefore be sub-optimal. Supplementation of the pasture with dry roughage may improve rumination, the rumen environment and therefore also milk production performance. The aim of the study was to determine if strategic supplementation of lucerne hay will improve milk production, milk composition and the rumen environment of cows grazing high quality kikuyu/ryegrass during spring and receiving low levels of concentrate. Forty eight high producing Jersey cows were blocked and randomly allocated to one of the following treatments: control (no supplemental roughage), supplementation of 1.0 kg lucerne hay and supplementation of 2.0 kg lucerne hay after morning milking. Cows received 5 kg of dairy concentrate per day during milking. Cows grazed as one group and pasture was allocated to ensure a post grazing height of 10-12 on the rising plate meter (5-6 cm). The average post grazing pasture height for the experimental period was 10.83±1.68 (n=73) on the RPM (5.42 cm). There were no differences (P >0.10) between the treatments for 4% fat corrected milk production, which were 22.2 kg/d for the control, and 22.5 kg/d and 22.9 kg/d for the 1 kg and 2 kg lucerne treatments respectively. Milk fat and protein percentage was not affected (P >0.10) by supplementation of lucerne hay. The milk lactose content of cows receiving the control and 1 kg lucerne hay treatments were higher (P <0.05) than those of cows receiving the 2 kg lucerne hay treatment. Eight rumen cannulated Jersey cows were randomly allocated to either the control or the 2 kg lucerne hay treatment in a cross-over design. These cows grazed together with the cows of the production study and received the same dairy concentrate. Rumen pH was measured for 48 hours with 10 minute intervals using an automated pH logging system. Rumen samples were taken at 08:00, 14:00, 20:00 and 02:00 and were analysed for ammonia-nitrogen (NH3-N), volatile fatty acids (VFA) and pH. An in sacco study was conducted to determine DM and neutral detergent fibre (NDF) disappearance of ryegrass. There were no differences (P >0.10) between treatments in overall mean pH, measured with either the logging systems or with the portable pH meters averaging 6.18 and 6.11 for cows receiving the control and the 2 kg lucerne treatment respectively. The mean rumen NH3-N did not differ (P >0.10) between treatments. The mean concentration of acetic acid and the total VFA concentration was higher (P <0.05) for cows receiving the 2 kg lucerne treatment compared to the control. There were no differences (P >0.10) between treatments in the DM or NDF disappearance of ryegrass after 24 hours. Supplementation of lucerne hay to cows grazing well managed kikuyu-ryegrass pasture during spring did not improve milk production, milk composition, rumen pH or in situ NDF disappearance of ryegrass Results suggest that cows grazing kikuyu/ryegrass pastures supplemented with low levels of concentrate consume sufficient eNDF to maintain a favourable rumen environment and normal milk composition. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

Energy is the first-limiting nutrient for cows grazing pasture therefore, energy supplementation is necessary for high producing animals. In pasture-based systems, the concentrate is fed twice a day in the dairy parlour during the milking procedure. Consumption of large amounts of fermentable carbohydrates results in a drop in rumen pH and this may induce rumen acidosis. This may lead to reduced intake, lower fibre digestion and depressed milk yield. Supplemental yeast offer great possibilities in stabilising the rumen fermentation patterns and, therefore, improving dry matter intakes (DMI). This may increase milk production, milk composition parameters, rumen volatile fatty acid concentrations (VFA) which leads to higher profits. Investigating these responses, a trial was conducted, where live yeast (Levucell SC 10 ME-Titan) was supplemented to Jersey cows grazing ryegrass/kikuyu pastures, supplemented with 6 kg (as is) dairy concentrate per day split over two milking periods. Thirty multiparous high-producing Jersey cows between 30 and 120 days in milk (DIM) were selected, blocked and randomly allocated to control (no yeast) or live yeast treatment groups. Ten fistulated lactating cows were added in a cross-over design (two periods and two treatments) and all 40 cows strip grazed Italian ryegrass (Lollium multiflorum) and kikuyu pastures as one group. A new pasture strip was allocated after each milking and pasture was measured using a rising plate meter (RPM). The yeast product Levucell SC 10 ME – Titan containing Saccharomyces cerevisiae CNCM I-1077 was supplied by Lallemand S.A.S (19 rue des Briquetiers, 31702 Blagnac cedex, France). The Levucell SC 10 ME – Titan is a micro-encapsulated formulation for premix and pelleted feeds. The yeast treatment group had the yeast pelleted in with the dairy concentrate at a concentration of 167 g of yeast per ton of concentrate, to obtain the required intake of 1 g yeast per cow per day as specified by Lallemand. Milk yields were recorded daily and composite milk samples were taken every two weeks to determine, milk fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count (SCC) contents. The fistulated cows were adapted to their respective diets and treatments for 21 days after which the pH measurment, rumen fluid sampling, and In sacco study were conducted. Milk yield, 4% fat corrected milk (FCM) yield, milk protein and lactose percentages, SCC, body condition score (BCS), and live weight did not differ (P > 0.05) between treatments. The milk fat% however, was higher for the yeast supplemented cows at 4.24% compared to the control group of cows of 3.99% (P < 0.05). The mean acetic and total VFA concentration (mmol/L) for the control treatment was higher compared to the yeast treatment (P < 0.05). There was no difference in the fermentation patterns of VFA, the pH and NH3-N values measured between treatments (P > 0.05). The mean In sacco neutral detergent fibre (NDF), organic matter (OM) and DM disappearance was higher for the yeast treatment group of cows after a 12 and 24 hour incubation compared to the control group (P < 0.05). The mean ruminal NDF disappearance of ryegrass in cows supplemented with yeast increased by 11.9% and 6.3% compared to the control at the 12 and 24 hour incubation periods, respectively. With higher fibre digestibilities in the rumen and more acetate available at the mammary gland and subsequently higher milk fat percentages, the yeast effects on stimulating the cellulolytic bacteria in the rumen, may be a possible explanation for the results in the current study and it is well documented in previous studies. Live yeast supplementation resulted in higher milk fat percentages which improved milk price. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Based on periodic clipping of a fertilized pasture plot in the Peace River region in 1977 and 1979, accumulated dry matter production of a timothy, red fescue and alsike clover mix was found to be linearly related to accumulated transpiration during the active growing season, with a growth/transpiration ratio of 0.026 t ha⁻¹ /(mm H₂O)-The effect of fertilizer level and cutting management on dry matter production is discussed. Energy balance/Bowen ratio measurements of evapo-transpiration (E) in 1977, 1978 and 1979 showed that daytime E can be calculated for energy limiting conditions using the Priestley-Taylor formula with α = 1.26 ± 0.05. Daytime net radiation required in this formula was estimated to within 15%, using the Idso-Jackson longwave radiation equation and daily solar radiation data from a regional climate station 50 km away. During water supply limiting conditions E was found to be linearly related to root zone water storage. Root zone drainage was found to be negligible in this soil, which has a high bulk density subsoil. A simple model for calculating the course of pasture growth during the growing season at Sunset Prairie Community Pasture is described. The model is composed of a single-layer root zone water balance submodel and a relationship between dry matter production and transpiration. The water balance submodel estimates daily transpiration and requires daily values of rainfall, solar radiation and maximum and minimum air temperature. It also requires crop albedo and an estimate of the initial root zone water storage. Estimates of root zone water storage during the three growing seasons agreed well with gravimetric and neutron moisture probe measurements. The model, using the above growth/transpiration ratio, was found to estimate hay growth during the droughty growing season in 1978 to within 15% of measured values. An effective growth/transpiration ratio of 0.013 t ha ⁻¹/mm was required to account for the growth of pasture subjected to a simulated monthly grazing rotation. / Land and Food Systems, Faculty of / Graduate

Made available in DSpace on 2016-01-26T18:56:21Z (GMT). No. of bitstreams: 1 dissertacao.pdf: 398265 bytes, checksum: 21b224b71f75cac0dfab27ababfeb591 (MD5) Previous issue date: 2009-11-27 / Knowledge of the genetic variability of Brachiaria ruziziensis is required before you start a breeding program. This study investigated the genetic variability of 37 samples of Brachiaria ruziziensis, from the collection held by EMBRAPA Dairy Cattle by molecular markers and long primers. The DNA was extracted from leaves by CTAB method, we used 14 decamer primers and primers 9 long. The data were used for analysis of molecular variance (AMOVA) using the squared distances (Excoffier et al., 1992) using the program Arlequin (Excoffier et al., 2006). We found variation between species of 47.42% and 36.07% for RAPD primers and long, respectively and within the species observed variation of 52.58% and 63.93%. A dendrogram was constructed with the UPGMA clustering algorithm (Unweighted Pair-Group Method using an Arithmetic Average) using this analysis to the program NTSYS 2.0 (ROHLF 1998). Both markers were able to group the samples where genotypes 1 to 5 the most similar to each other. RAPD using primers short and long primers are effective to estimate the variability in Brachiaria ruziziensis. / O conhecimento da variabilidade genética de Brachiaria ruziziensis é necessário antes de iniciar-se um programa de melhoramento. Este trabalho objetivou estudar a variabilidade genética de 37 amostras de Brachiaria ruziziensis, provenientes de coleta realizada pela EMBRAPA Gado de leite por meio de marcadores moleculares RAPD e primers longos. O DNA das folhas foi extraído pelo método CTAB, utilizaram-se 14 primers decâmeros e 9 primers longos. Os dados foram utilizados para análise de variância molecular (AMOVA) utilizando-se as distâncias ao quadrado (EXCOFFIER et al., 1992) com auxílio do programa Arlequin (EXCOFFIER et al., 2006). Encontrou-se variação entre espécies de 47,42% e 36,07% para RAPD e primers longos, respectivamente e dentro da espécies observou-se variação de 52,58% e 63,93%. Foi construído um dendrograma com o algoritmo de agrupamento UPGMA (Unweighted Pair-Group Method Using an Arithmetic Average) utilizando-se para essa análise o programa NTSYS 2.0 (ROHLF, 1998).Ambos marcadores conseguiram agrupar os genótipos onde as amostras 1 a 5 foram as mais semelhantes entre si. RAPD utilizando-se primers curtos e primers longos são eficientes para estimar a variabilidade em Brachiaria ruziziensis.

Made available in DSpace on 2016-07-18T17:51:05Z (GMT). No. of bitstreams: 1 dissertacao.pdf: 398265 bytes, checksum: 21b224b71f75cac0dfab27ababfeb591 (MD5) Previous issue date: 2009-11-27 / Knowledge of the genetic variability of Brachiaria ruziziensis is required before you start a breeding program. This study investigated the genetic variability of 37 samples of Brachiaria ruziziensis, from the collection held by EMBRAPA Dairy Cattle by molecular markers and long primers. The DNA was extracted from leaves by CTAB method, we used 14 decamer primers and primers 9 long. The data were used for analysis of molecular variance (AMOVA) using the squared distances (Excoffier et al., 1992) using the program Arlequin (Excoffier et al., 2006). We found variation between species of 47.42% and 36.07% for RAPD primers and long, respectively and within the species observed variation of 52.58% and 63.93%. A dendrogram was constructed with the UPGMA clustering algorithm (Unweighted Pair-Group Method using an Arithmetic Average) using this analysis to the program NTSYS 2.0 (ROHLF 1998). Both markers were able to group the samples where genotypes 1 to 5 the most similar to each other. RAPD using primers short and long primers are effective to estimate the variability in Brachiaria ruziziensis. / O conhecimento da variabilidade genética de Brachiaria ruziziensis é necessário antes de iniciar-se um programa de melhoramento. Este trabalho objetivou estudar a variabilidade genética de 37 amostras de Brachiaria ruziziensis, provenientes de coleta realizada pela EMBRAPA Gado de leite por meio de marcadores moleculares RAPD e primers longos. O DNA das folhas foi extraído pelo método CTAB, utilizaram-se 14 primers decâmeros e 9 primers longos. Os dados foram utilizados para análise de variância molecular (AMOVA) utilizando-se as distâncias ao quadrado (EXCOFFIER et al., 1992) com auxílio do programa Arlequin (EXCOFFIER et al., 2006). Encontrou-se variação entre espécies de 47,42% e 36,07% para RAPD e primers longos, respectivamente e dentro da espécies observou-se variação de 52,58% e 63,93%. Foi construído um dendrograma com o algoritmo de agrupamento UPGMA (Unweighted Pair-Group Method Using an Arithmetic Average) utilizando-se para essa análise o programa NTSYS 2.0 (ROHLF, 1998).Ambos marcadores conseguiram agrupar os genótipos onde as amostras 1 a 5 foram as mais semelhantes entre si. RAPD utilizando-se primers curtos e primers longos são eficientes para estimar a variabilidade em Brachiaria ruziziensis.

Kikuyu is well adapted to the main milk producing areas of the Southern Cape region of South Africa. The strategic incorporation of different types of temperate grasses into kikuyu pastures can increase the seasonal dry matter production, pasture quality, and milk production attainable from these pastures. To determine whether there is production and economical differences between kikuyu based pasture systems, a trial was conducted on the Outeniqua Research Farm near George. The three pasture treatments, namely italian, westerwold, and perennial ryegrass over-sown into kikuyu, were tested. Forty-five Jersey cows were blocked and cows within blocks were randomly allocated to the treatments. The cows received 9 kilograms of pasture (on a dry matter basis) per cow per day, and four kilograms of concentrate per cow per day. Milk production was recorded daily, and milk composition was determined monthly. The cows were weighed and body condition scored monthly. The perennial ryegrass pasture treatment had a higher milk production per hectare (32288 kg/ha) than the westerwold ryegrass pasture treatment (29761 kg/ha) but did not differ from the italian ryegrass pasture treatment (30446 kg/ha). The italian ryegrass pasture treatment had a higher milk protein percentage than the perennial ryegrass pasture treatment (3.84% vs. 3.64%) but did not differ from the westerwold ryegrass pasture treatment (3.75%). When the three pasture treatments were economically compared, the italian ryegrass pasture treatment had the highest margin over specified costs per hectare (R 36,565.03), followed by the perennial (R 33,889.14) and westerwold (R 29,468.09) ryegrass pasture treatments. From the results it seems that the italian ryegrass pasture treatment is the best choice for a kikuyu based pasture system in the Southern Cape region of South Africa. A high level of concentrate supplementation could increase energy intake of grazing dairy cows, but might also reduce fibre digestion within the rumens of high producing dairy cows. To test this hypothesis, two trials were conducted, one during October and November 2007, and the other during March 2008. In both trials twelve rumen cannulated cows were allocated to four groups. Two groups were allocated to each pasture treatment, namely perennial and westerwold ryegrass over-sown into kikuyu. Within each pasture treatment, one group received 4 kg of concentrate per cow per day, and the other 8 kg of concentrate per day. Pasture was allocated at 9 kg per day (DM). Cows were adapted for ten days, after which ruminal pH, and ammonia nitrogen and volatile fatty acid concentration data was collected. An in sacco study was conducted to determine the neutral detergent fibre degradability. After the data was collected, the two groups within each pasture treatment swapped concentrate levels; were adapted, and the same data as described above was collected. During both trials reductions in ruminal pH were observed when a higher amount of concentrate was supplemented. During the first trial there was a significant increase in the time that the ruminal pH remained below pH 5.8 on the westerwold ryegrass pasture treatment (from 80 minutes when the cows received 4 kg of concentrate per day, to 375 minutes when it was increased to 8 kg of concentrate per day). A decrease in neutral detergent fibre degradability was also seen. During the second trial, the percentage of NDF disappearance decreased from 8.45% over a twelve hour period when 4 kg of concentrate was fed, to 4.51% when 8 kg of concentrate was fed on the perennial ryegrass pasture treatment. From the results it appears that feeding a higher level of concentrate supplementation to high producing dairy cows grazing kikuyu pasture systems has a negative effect on neutral detergent fibre digestion within the rumen. It appears that feeding a moderate level of concentrate supplementation when cows are on pasture based systems is more beneficial to the rumen environment and decreases the possibility of sub-clinical ruminal acidosis when cows grazed ryegrass dominant pastures, but had a less pronounced effect when the dominant pasture specie was kikuyu. Future research could examine the relationship between the level of concentrate supplementation and pasture specie more closely, as it would be interesting to find the optimal ratios for each pasture specie. Copyright / Dissertation (MScAgric)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

<p><i>Colletotrichum sublineolum</i> is the causal agent of sorghum anthracnose, a very common and destructive fungal disease in warm and humid areas, especially in West and Central Africa. Use of host plant resistance is considered as the most important and effective control option for sorghum diseases. To achieve this goal, identification and mapping resistance genes is essential. In this study, we used an isolate of <i>C.</i> <i>sublineolum</i>, CsGL1, to screen our sorghum germplasm and identified a resistant inbred line, P9830. We developed a mapping population from a cross between P9830 and a susceptible line, TAM428, for this research. The population was advanced to the F₆ generation. Progenies were phenotyped at F₂, F₃ and F₆ generations for disease resistance against the pathogen, CsGL1. In the F₂ generation, 460 individuals showed resistance and 149 individuals showed susceptibility to CsGL1. This result fits the 3:1 segregation pattern expected for resistance controlled by a single gene. Bulked segregant analysis with next generation sequencing was used on selected F₆ recombinant inbred lines. A significant peak containing 153 SNPs was observed on the distal end of the long arm of chromosome 8. To verify resistance to CsGL1 was controlled by genes in this region, indel and SNP markers were used between 59.4Mbp and 60.6Mbp on chromosome 8 to fine map the resistance locus. One SNP marker located in the gene <i>Sobic.008G166400</i> co-segregated with resistance, and another two indel markers were discovered to be tightly linked to the resistance locus. These three PCR-based SNP markers would be useful for marker-assisted selection for improving anthracnose resistance against CsGL1. Two candidate genes, <i>Sobic.008G166400</i> and <i>Sobic.008G166550</i>, were found in the locus. Both of the genes encode LRR proteins implicated in plant disease defense response. The identity of DNA sequence between these two candidate genes is 94.1%, possibly the result of tandem duplication. Another possible ortholog in the region is <i>Sobic.008G167500</i>. Quantitative PCR analysis showed that the expression level of <i>Sobic.008G166400</i> didn’t change significantly in a resistant RIL, 17-12 but was induced in a susceptible RIL, 13-31, after CsGL1 infection. In conclusion, we mapped two candidate genes conferring resistant to CsGL1 on chromosome 8, and <i>Sobic.008G166400</i> is more likely of the two to be determined as the gene controlling resistance to CsGL1. </p>

<p><a>In the United States and Canada, weed interference in corn (<i>Zea mays </i>L.) costs farmers nearly $4 billion per year. Weed control has been achieved primarily through herbicides and tillage. As no-till corn acres have increased, dependence on herbicides has also increased. Herbicide-resistant weed infestations have pressured many growers into other weed management practices, such as adding winter cover crops into crop rotations. Field experiments were conducted in 2017 through 2018 and 2018 through 2019 at three locations in Indiana to determine residual herbicide efficacy applied at cereal rye termination and after corn planting in cereal rye (<i>Secale cereale</i> L.) and winter-fallow no-till corn. Weed biomass and density suppression was dependent on weed species and was influenced by cereal rye biomass at termination. Weed biomass was suppressed by up to 84% by cereal rye alone. Weed biomass reduction by a residual herbicide premix was similar in both cereal rye and non-cover crop treatments in most site-years, however cereal rye and the residual herbicide premix together resulted in decreased giant ragweed (<i>Ambrosia trifida </i>L.) and summer annual grass biomass compared to the residual herbicide premix applied alone in one site year. Late-season grass weed density was reduced by residual herbicides, but was unaffected by cover crop treatment. Late-season common cocklebur density and biomass increased in cereal rye treatments compared to non-cover crop treatments. </a></p> <p>Other field experiments were conducted at the same locations in 2017 through 2018 and 2018 through 2019 to determine the effect of cover crop species, termination timing, and chemical cover crop termination strategies on weed control and corn yield. Crimson cover (<i>Trifolium incarnatum </i>L.), cereal rye, and a cereal rye/crimson clover mix were terminated two weeks before, at, and two weeks after corn planting. All plots were terminated using glyphosate and atrazine, however others were also terminated with dicamba and acetochlor. The addition of acetochlor generally reduced early-season weed biomass or density, but not in cereal rye and cover crop mix treatments that were terminated at or after corn planting. Late-season summer annual grass biomass was reduced when cover crop biomass at termination was over 8000 kg ha^-1. Late-season common cocklebur density in 2018 was 450% to 800% higher in cover crops containing cereal rye, compared to crimson clover treatments. Corn yield was reduced by 23% to 67% in cereal rye and cover crop mix treatments in two out of three site-years in 2018, however corn yield was not reduced by crimson clover in either year, nor by cereal rye or the cover crop mix in 2019.</p>

<p>  </p> <p>In Midwestern soybean [<em>Glycine max </em>(L.) Merr.] systems, especially in Indiana, three summer annual weed species are among the most common and troublesome for soybean producers: tall waterhemp (<em>Amaranthus tuberculatus</em>), giant ragweed (<em>Ambrosia trifida</em>), and horseweed (<em>Conyza canadensis</em>). Evolved resistance to current herbicides [e.g. glyphosate and acetolactate synthase (ALS) ihibitors], coupled with a dearth of new herbicide active ingredients being commercialized in the last two decades, has made controlling these problematic weeds particularly challenging. Trifludimoxazin is a novel protoporphyrinogen oxidase (PPO)-inhibiting herbicide that is currently under development for use in soybean and is likely to be commercially applied either alone or in combination with the herbicide saflufenacil. Research herein was conducted to investigate foliar control of tall waterhemp (including genotypes that are resistant to applications of other PPO inhibitors), giant ragweed, and horseweed following applications of trifludimoxazin alone and in combination with other herbicides. Additionally, the efficacy of soil-residual applications of trifludimoxazin and trifludimoxazin plus saflufenacil was evaluated for tall waterhemp and compared to other preemergence herbicides commonly used in soybean. Finally, soybean response to preplant applications of trifludimoxazin and trifludimoxazin plus saflufenacil at various preplant timings was investigated along with impact of adding the WSSA Group 15 herbicides acetochlor, pyroxasulfone, and <em>S</em>-metolachlor to preemergence applications of trifludimoxazin plus saflufenacil.</p> <p>Applications of 12.5 g ha-1 trifludimoxazin were highly efficacious in foliar applications on tall waterhemp (94% control) at 28 days after application (DAA), less effective when applied to giant ragweed (78% control, 21 DAA), and ineffective on horseweed (9% control, 28 DAA). When applied in combination with glufosinate, glyphosate, paraquat, or saflufenacil, foliar control for these species was 91% to 100%, except for trifludimoxazin plus glyphosate applied to a glyphosate-resistant population of horseweed (17%). Furthermore, foliar efficacy of trifludimoxazin applied to tall waterhemp or Palmer amaranth (<em>Amaranthus palmeri</em>) was not impacted by the presence of target-site mutations (ΔG210 or R128 in waterhemp, ΔG210 or V361A in Palmer amaranth) that confered resistance to saflufenacil and fomesafen.</p> <p>Near complete soil residual control [≥ 98% at 2 weeks after application (WAA)] of tall waterhemp was initially observed with 12.5 to 50 g ha-1 of trifludimoxazin but were less effective (39% to 69%) relative to commercial standards of pyroxasulfone (91%) or sulfentrazone (95%) by 6 WAA. Combining saflufenacil at 25 or 50 g ha-1 with soil-residual applications of trifludimoxazin improved efficacy on tall waterhemp at 6 WAA relative to trifludimoxazin alone. With the exception of 12.5 + 25 g ha-1 (74%), applications of trifludimoxazin plus saflufenacil, respectively, resulted in comparable residual tall waterhemp control (84% to 92%) as the commercial standards. </p> <p>Soybean injury following applications of trifludimoxazin was relatively low (< 10%), regardless of preplant application timing [0 to 28 days before planting (DBP)] or rate (6.25 to 25 g ha-1). However, the addition of saflufenacil increased soybean injury, especially when environmental conditions were more conducive to soybean response. For instance, at Pinney Purdue Agriculture Center (PPAC) in 2019 soybean injury 4 weeks after planting (WAP) was 28%, soybean population was reduced by 39%, and yield was reduced by 27% when trifludimoxazin plus saflufenacil was applied at 25 + 50 g ha-1. The experimental conditions that corresponded to this elevated soybean injury were coarse-texture soil, low temperatures, and high precipitation at the time of soybean emergence. Lower rates of this herbicide combination resulted in less injury, and soybean response was minimized (≤ 8%) when applications were made at least 14 DBP. The addition of Group 15 herbicides to applications of trifludimoxazin plus saflufenacil at planting did not impact soybean response, except for at PPAC in 2019, where the addition of acetochlor (51%) or pyroxasulfone (46%) to 25 + 50 g ha-1 was greater than without these Group 15 herbicides at 4 WAP (22%). Field research indicated soybean response to combinations of trifludimoxazin plus saflufenacil differed by cultivar in some instances, and greenhouse experiments determined the response was attributable to differential soybean cultivar sensitivity to the saflufenacil component of the mixture.  </p>