Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-06-14T19:55:04Z No. of bitstreams: 1 2016 - Jucielle Rocha Ferreira.pdf: 1303291 bytes, checksum: b1975fe6fff5a1d5a4d85aa07760fab8 (MD5) / Made available in DSpace on 2017-06-14T19:55:04Z (GMT). No. of bitstreams: 1 2016 - Jucielle Rocha Ferreira.pdf: 1303291 bytes, checksum: b1975fe6fff5a1d5a4d85aa07760fab8 (MD5) Previous issue date: 2016-03-15 / CNPq / FAPERJ / In organic farming, green manuring and mulching are recommended to maintain or recuperate soil fertility and promote nutrients cycling, besides manage weeds population. Weeds can cause damages to economic crops by competition for water, light and nutrients in cultivated areas. This work aimed to evaluate maize yield and weeds population after green manures cultivation. The experiment was conducted in an Ultisol, placed at Integrated System of Agroecological Production, in Serop?dica, RJ, from October 2014 to June 2015. The experimental design was of randomized blocks, with six treatments and four replications. The treatments involved previous cultivation with sunnhemp (Crotalaria juncea), jack bean (Canavalia ensiformis), velvet bean (Mucuna aterrima), sunflower (Helianthus annuus), sorghum (Sorghum bicolor), and fallow. The green manures were sowed in October, being cultivated during 113 days after sowing. After that, they were cut. Five days after the cut and deposition of the green manures residues in the soil surface, it was sowed maize var. Caatingueiro, adopting spacing of 1,0 m between lines and density of five seeds per linear meter, with a population of 50.000 plants per hectare. Weeds population was evaluated at 15, 30, 45, and 60 days after maize sowing, collecting samples of weeds for identification and quantification of species, and dry biomass production. The obtained data were used for determining of phytosocial indexes. Dry biomass of green manures was greater for the treatments sunnhemp and sorghum. On the other hand, dry biomass of weeds was greater in the treatment velvet bean. Yield of maize without straw; yield of shoot biomass; diameter, length and N contents in grains and shoot did not show significant differences between treatments. Weeds population compositions is influenced by the soil cover crops. The use of sorghum was efficient regarding to biomass production and weeds control. Sunnhemp and sorghum produced biomass values above the recommended amounts for no-tillage system. / Em sistemas org?nicos de produ??o, a aduba??o verde e o uso de cobertura morta s?o recomendados, de forma a manter ou recuperar a fertilidade dos solos e promover a ciclagem de nutrientes, al?m de manejar a popula??o de plantas espont?neas. Esp?cies espont?neas podem causar preju?zos ?s culturas de interesse econ?mico, o que pode ser explicado pela competi??o por ?gua, luz e nutrientes nas ?reas cultivadas. Objetivou-se nesse trabalho avaliar o desempenho agron?mico de milho verde e a din?mica populacional de plantas espont?neas ap?s cultivo de adubos verdes. O experimento foi realizado em um Planossolo, localizado no Sistema Integrado de Produ??o Agroecol?gica, no munic?pio de Serop?dica, RJ, no per?odo de outubro de 2014 a junho de 2015. O delineamento experimental adotado foi de blocos casualizados, com seis tratamentos e quatro repeti??es. Os tratamentos constaram de cultivo pr?vio de crotal?ria (Crotalaria juncea), feij?o de porco (Canavalia ensiformis), mucuna preta (Mucuna aterrima), girassol (Helianthus annuus), sorgo (Sorghum bicolor) e pousio com vegeta??o espont?nea. A semeadura dos adubos verdes foi realizada no m?s de outubro e seu cultivo se deu at? os 113 dias ap?s a semeadura, realizando-se ent?o sua ro?ada. Cinco dias ap?s a ro?ada e deposi??o dos res?duos culturais ao solo, foi realizada semeadura direta do milho variedade Caatingueiro, com espa?amento de 1,0 m entre linhas e densidade de cinco sementes por m-1 linear, totalizando 50.000 plantas por hectare. A popula??o das plantas espont?neas foi avaliada aos 15, 30, 45 e 60 dias ap?s o plantio do milho, atrav?s da coleta de amostras da popula??o espont?nea para identifica??o e quantifica??o das esp?cies e da produ??o da biomassa seca. Os dados obtidos foram utilizados na determina??o de ?ndices fitossociol?gicos. A biomassa seca dos adubos verdes foi maior para os tratamentos crotal?ria e sorgo. Por sua vez, a biomassa seca das plantas espont?neas foi maior na presen?a da cobertura do solo com mucuna preta. Quanto ? produtividade de espigas despalhadas, produtividade de biomassa a?rea do milho, di?metro, comprimento e teores de N no gr?o e na parte a?rea, n?o houve diferen?a significativa entre os tratamentos. A popula??o de plantas espont?neas foi influenciada em sua composi??o, em fun??o dos adubos verdes cultivados. A cobertura com sorgo mostrou-se eficiente quanto ? produ??o de biomassa vegetal e controle de plantas espont?neas. A crotal?ria e o sorgo atingiram quantidade de biomassa acima da recomendada para adequada implanta??o do sistema plantio direto.

Winter rotational cover crops (WRCC) are often used to boost soil fertility and plant nutrition. However, selection and use of WRCC for soil physical improvement is usually overlooked. The objective of this study was to determine the effects of WRCC on soil strength, aggregate stability and water conservation of a hardsetting soil. The soil physical properties were determined after four rotations of growing monocultures of vetch (Vicia dasycarpa cv. Max), lupin (Lupinus angustifolius cv. Tanjil) and oats (Avena sativa cv. Sederberg) and after two rotations of growing bicultures of oats (Avena sativa cv. Pallinup) and vetch (Vicia dasycarpa cv. Max) across two soil layers, 0 to 15 cm and 15 to 30 cm. The individual WRCC and a weedy fallow constituted the treatments in the monoculture study whilst in the biculture study the various combinations of WRCC namely; 90% oat plus 10% vetch (O90V10); 70% oat plus 30% vetch (O70V30) and 50% oat plus 50% vetch (O50V50) and a weedy fallow constituted the treatments. After four rotations with cover crop monocultures, oats significantly (P ≤ 0.05) reduced penetration resistance (PR) whilst vetch increased PR in both soil layers compared to the weedy fallow control. The effect of the biculture treatments was only experienced within the 15 to 30 cm depth. The treatments O50V50 and O70V30 increased the PR compared to the control. The WRCC in monoculture significantly increased the soil aggregate stability relative to the control in both soil layers. Vetch, lupin and oats resulted in a 41.7%; 20.4% and 15.7% increase in MWD in the 0 to 15 cm soil layer and 47.2%; 44.2% and 39.7% in the 15 to 30 cm depth, respectively. An increase in aggregate stability was associated with increased macro-aggregation. Under the biculture, WRCC slightly increased, non- significantly, the aggregate stability. Both hot water and dilute acid extractable polysaccharides showed no significant correlation with aggregate stability in the two studies. Oats monoculture resulted in a significant difference (P ≤ 0.05) on cumulative infiltration compared to the control. However, after 2 h vetch and lupin showed no significant difference from the control on cumulative infiltration. Oats resulted in a 7.8% increase in final infiltration rate (FIR) whilst vetch and lupin reduced FIR by 9% and 16.7% respectively, compared to the control. Bicultures of oats and vetch significantly (P ≤ 0.05) increased cumulative infiltration compared to the weedy fallow control. A similar significant increase in FIR was also observed under bicultures. The treatments O50V50; O90V10 and O70V30 resulted in a 163.3%; 113.3% and 105.4% increase in FIR respectively, compared to the control. Cover crop monocultures significantly (P ≤ 0.05) increased plant available water (PAW) compared to the weedy fallow, with vetch, oats and lupin resulting in a 28.3%; 22% and 23.9% increase respectively, in PAW. However, no significant differences were observed on PAW after two rotations with bicultures. Compared with winter weedy fallow, WRCC improved most of the soil physical properties under study, with the most suitable results expected under bicultures compared to monocultures. Under CA, selection of WRCC like oats, vetch and lupin, one should therefore take into consideration their effects on soil physical properties as a selection criterion and not biomass and fertility alone.

Fruit growers in Utah and other areas across the Intermountain West are faced with growing production challenges stemming from declining soil quality and water resources. Population growth presents challenges in terms of the cost and availability of land, but also presents opportunities in the form of new marketing options such as organic fruit. Few certified organic fruit orchards are operating in Utah currently, which is attributed to a lack of locally tested and adapted organic management practices. An organic peach orchard trial evaluated the effectiveness of different organic management approaches to enhance soil quality and conserve water without compromise to fruit tree growth and fertility. Two tree-row treatments: ‘straw mulch' (Triticum aestivum L.) and ‘living mulch’ (Lobularia maritima (L.) Desv.) were tested in combination with two alleyway groundcovers: ‘grass’ (Festuca rubra L. with Lolium perenne L.) and a legume, ‘Birdsfoot trefoil’ (Lotus corniculatus L.). The novel systems were compared with industry standards, tillage and weed fabric tree-rows with grass alleyways. Trefoil alleyway biomass deposited into tree-rows contributed an estimated 6.24 kg biomass and 0.21 kg total N/tree annually. Trefoil treatments had higher levels of organic carbon (C) and nitrogen (N), inorganic N, microbial biomass and enzyme activities, suggesting trefoil alleyways enhanced soil nutrient cycling, as well as C and N reserves in comparison to grass and tillage treatments. A functional gene array analysis was conducted to describe the mechanisms, microbial functional composition and diversity underlying the observed soil processes, however few differences were detected in soil community structure between soils under different orchard floor management. Significantly lower leaf δ15N in trees grown with trefoil compared to grass, and an association between root biomass, diameter and trunk cross-sectional area (TCSA) suggests nitrogen sources derived from the trefoil groundcover contributed to improved fruit tree vigor. Few differences resulted among orchard treatments for water use (mm/week). Trends indicated slightly higher water use in trefoil over grass, but not enough to offset observed soil quality and tree growth benefits. These findings suggest, trefoil alleyways may provide ecological benefits such as improved soil quality and efficient nutrient cycling, without substantial increases in water use.

Corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in Illinois has a significant impact on the economy and environmental footprint in the state and the Midwest region. Nutrient leaching from Midwestern agricultural fields is one of the major reasons for the hypoxic zone developed in the Gulf of Mexico. Winter-fallow and early spring (after fertilizer application) are the two most critical periods for nutrient leaching due to increased precipitation and availability of nutrients. Cover crops (CCs) in these seasons are a promising best management practice (BMP) to reduce nutrient leaching in the winter-fallow season. No-till (NT) and reduced tillage (RT) are some other BMPs that farmers in Illinois adopt to reduce erosion. The adoption of CCs is limited due to the lack of knowledge and data on the yield and environmental benefits of CCs in different climatic and soil regimes. Thereby, this doctoral dissertation addresses several critical questions about CC and tillage impacts in claypan soils of southern Illinois with four principal projects with multiple objectives. Research study 1 was a field experiment conducted from 2013-to 2021 to understand the effect of CCs (CCs vs. noCC) and two tillage (NT and RT) practices on soil nitrate-N leaching. The experimental design was a complete randomized design with CC treatments that had two levels (two crop rotations) corn-cereal rye (Secale cereale L.)-soybean-hairy vetch (Vicia villosa R.) [CcrShv] and corn-noCC-soybean-noCC [CncSnc] and tillage treatments with two levels (NT and RT) replicated three times in the field. Each plot had a pan lysimeter installed below the A horizon (22-30 cm depth) to collect water samples weekly or biweekly depending on the rainfall. The corn yield was significantly greater in RT rotations compared to NT rotations with a 36% increase in the yield in 2019 and 2021 corn rotations. The yield was significantly greater in CcrShv rotations compared to the CncSnc rotations. The greatest yield was observed in the interaction of CcrShv-RT in all years. This increase in yield is inversely correlated to the remaining soil N values when the N credit from CCs was not accounted for. Soil nitrate-N leaching was significantly greater in CcrShv rotations compared to the CncSnc rotation in 2021 indicating vetch CC biomass decomposition can lead to increased leaching losses if the window between CC termination and corn planting is not minimized. Precipitation during the early spring can play a vital role in flushing the newly applied fertilizer as well as the N released from decomposing CC residue. The excessively wet year of 2019 showed that N losses are dominated by both nitrate-N leaching and nitrous oxide emissions, but in a typical growing season N losses are dominated by leaching compared to emissions. Research study 2 was designed to better understand the N cycling and fate of applied N in a complete corn-soybean rotation in southern Illinois with CCs and tillage practices. The research was overlayed in the same field with the same crop rotation and tillage practices. In this study, 15N labeled urea fertilizer (9.2% atom) was applied before the corn and soybean seasons. Soil, water, and biomass samples were collected to understand N distribution in each pool. In the corn season in 2017 a significantly greater 15N recovery was observed in CC (CcrShv) plots compared to the noCC plots in the sample collected seven days after planting (DAP). In the CC and depth interaction, a significantly greater 15N recovery was observed in 15-30 cm depth showing that the increased macropores due to CCs can lead to subsurface movement of N through the topsoil. The 15N recovery in water samples was high in CncSnc rotations in the cereal rye season but was significantly greater in CcrShv rotations (8.95 kg ha-1) in hairy vetch seasons. In the two years of complete rotation, the cumulative 15N recovery (quantity derived from fertilizer in water) was significantly greater in CC rotation. In the corn plants, the 15N recovered from the soil was greater than the 15N recovered from fertilizer. This shows the importance of the residual N from prior fertilizer and organic matter input. In the cereal rye season, CCs recovered significantly greater 15N from fertilizer compared to noCC rotations, assuring that cereal rye is an effective nutrient scavenger. A similar pattern was observed in the hairy vetch season as well. However, the soybean 15N recovery was greater in noCC rotations compared to CC rotations. The third study was a field trial on CCs and tillage to understand their individual and combined impact on soil physical parameters. Soil physical parameters were first measured in 2014 and were repeated in 2021. Bulk density at the 0-5 cm depth was 5% lower in 2021 compared to 2014 with the lowest BD in CC rotations with RT practices. For the depth of 0-15 cm, the lowest BD was observed in CC rotation with RT but, the largest reduction was observed in the CC rotation with NT. The wet aggregate stability was improved from 15-28 % over the years in all rotations. The lowest percentage improvement was observed in noCC rotation with RT practice. Penetration resistance was significantly lower in CC plots for the depth of 0-2.5 cm. CCs further improved the time to runoff in plots even though the infiltration rates were not affected. Chemical soil health indices were not significant overtime for CCs or tillage practices. However, a large number of earthworm counts were observed in NT systems compared to RT systems. The final project was a field trial to identify the soil P response to the CC and tillage practices. For this study, three different CC rotations, [corn-cereal rye-soybean-hairy vetch / corn-cereal rye-soybean-oats+radish / corn-noCC-soybean-noCC] and two tillage practices (NT and RT) were used. Soil samples were collected after the corn harvest in 2015 and 2021 and were analyzed for soil Phosphorus (P), inorganic P fractions by Chan and Jackson method, and dissolved reactive phosphorus (DRP) in leachate. The soil Mehlich-3 and Bray-1 P values indicate a great concentration of P in 0-15 cm depth for both years. More refined sampling in 2021 showed that the majority of P in 0-15 cm depth concentrates at the near-surface soil, in 0-5 cm depth irrespective of the CC and tillage treatment. Inorganic soil P fractions were not significantly different between CCs or tillage practices over time. Yet, irrespective of the treatment the non- labile P forms increased in 2021in the soil compared to 2015. The average and cumulative DRP values were highly dependent on the precipitation amounts and timing. However, in general, NT systems had greater average and cumulative DRP leaching compared to RT in both years. In general, CCs in the winter-fallow season is a good recommendation for farms that seek to maximize their production with a minimal environmental footprint. In the long run, CCs can improve soil physical and chemical properties which ultimately can increase the yield potential for corn and soybean. The added benefit of N credit due to leguminous CCs can reduce the fertilizer inputs. The CC benefits including the reduction in nutrient leaching depend on the type of CCs used in the field. More importantly, the CC termination time will be critical to obtain the maximum benefit of CCs. Even though the NT practices improve soil physical properties, long-term NT can increase the risk of soil P stratification in near-surface soils and can ultimately lead to more P loss via erosion, runoff, and soil water leaching. However, the combined use of CC and NT practices can help minimize the potential for erosion and runoff.

No description available.

There is growing interest within the agricultural industry on how cover crop systems affect soil health and economic productivity in integrated crop-livestock systems. This study investigated the combined effects of cover crop species; no-till and conventional till; and grazed (G) and un-grazed (UG) in a continuous corn (Zea mays) production system in east-central Mississippi. Cover crops were established in the fall of 2019 and 2020 in two separate field studies. Corn yield was not affected by grazing or tillage but was affected by cover crop species. We then compared the difference in cover crop species treatments with their respective corn yield and observed the greatest net return with the control ($252.09 ac-1). Organic matter was greater with the G area (1.03%) as compared to the UG (0.88%). Grazing resulted in bulk densities of 1.45 and 1.47 g cm3-1 for UG and G, respectively.

To combat herbicide resistance among weeds, non-herbicide methods of control, such as cover crops, are becoming widely adapted. Experiments were conducted to determine how to effectively establish and manage cover crops in order to suppress tall waterhemp and Italian ryegrass and to assess their overall impact on soybean growth and yield. Various cover crop establishment methods were evaluated, and it was determined that interseeding at the R7 growth stage of soybean was the least effective method for proper cover crop establishment. Biomass data demonstrated that interseeding created the least amountof cover crop biomass, with no differences found among the other establishment methods that included drilling and sowing broadcast. At soybean planting timing, treatments with tillage had greater control of tall waterhemp than those without tillage. Wheat was shown to have the greatest weed suppressive capabilities, largely due to its ability to create high levels of residual biomass. Daikon radish produced the least biomass residue and had the poorest tall waterhemp control. The termination experiment of Elbon rye determined that treatments with rolling could impact soybean emergence and plant height largely due to dense biomass that lay flat onto the soil surface

No description available.

Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops (CCs) or soil organic matter (SOM). Recent research successfully predicted the contribution of N from SOM and CCs to corn (Zea mays L.) in Pennsylvania. The objective of this work was to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied CC residues and the relationship between their chemical composition and decomposition rate. For the first objective, 83 N response trials were conducted in different regions of Virginia across 9 years using a randomized complete block design with four replications. The model was able to explain 47% and 15% of variability in unfertilized corn yield (RMSE = 1.6 Mg ha-1) and economical optimum N rate (EONR) (RMSE = 30 kg N ha-1) respectively. Efforts to improve the model by adding economically unresponsive sites improved the model performance to explain 45% of the variability in EONR. For the second objective, a lab incubation was performed to compare carbon (C) and N mineralization from four different CCs {Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. ANOVA test revealed that the effects of CC species, incubation days and their interaction had a significant effect on mass decomposed, plant biochemical composition and net N mineralization. Variation in mass loss was positively related to lignin content for all the CCs while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR. Net N mineralization was highest in HV followed by R, Cc and CR amended soils. / Master of Science / Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops or soil organic matter, both of which can influence crop N need. Recent research successfully predicted the contribution of N from cover crops and soil to corn (Zea mays L.) in Pennsylvania. The objectives of this work were to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied cover crop residues and the relationship between their chemical composition and decomposition rate. The Pennsylvania-developed model was able to successfully estimate the economical optimum N rate for corn and predict the yield of unfertilized corn. Corn yield did not increase with increasing N rates in some fields. When these sites were omitted, the accuracy of the model improved. For the second objective, a lab incubation study was performed comparing C and N released from Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. Variation in mass loss was positively related to lignin content for all the cover crops while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR.

Agroecosystem sustainability as a framework for agriculture production systems requires attention to detail to multiple facets of the underlying production system. Production systems must achieve optimal cash crop yields while remaining profitable. Likewise, production practices must be tailored to reduce its environmental footprint. Identifying practices that encourage improved soil physical and chemical properties while maintaining yields have largely been challenging. Cover crops have been an integral part of the conversation regarding practices that can generally improve those properties of soil responsible for overall soil health. Use of winter cereal cover crops (WCCC’s) have shown promise as a tool for reducing soil and nutrient run-off, thereby reducing nitrogen (N) and phosphorus (P) nonpoint source pollution in the Upper Mississippi River Basin (UMRB). However, corn-cash crop yield penalties are often incurred following the use of WCCC’s such as winter cereal rye (Secale cereal) (WCR), as N is immobilized by cover crop residues in the decomposition processes. Additionally, traditional planting methods of cover crops have resulted in reductions of harvestable populations of corn and soybeans. These problems indicate a necessity for novel cover crop planting methods that reduce the consequential outcomes of implementing traditional cover crop practices. Using a method called “Skipping the corn row” (STCR), otherwise identified as “precision planted” cover crops, we aimed to reduce the cash crop yield-limiting interactions of cover crop residues within the cash crop row. We hypothesized that removing cover crop biomass from the subsequently planted cash crop row (chapter 1) could minimize N immobilization by residues, thereby increasing our subsequent yield potential and economic optimum return to N (EORN). In novel cover crop planting methods preceding soybeans (chapter 3), our hypothesis indicated that mixtures of WCR and crimson clover (Trifolium incarnatum) would impact biomass accumulation of weed communities, while novel measures that allowed for reduced seeding rates would permit competitive soybean yields while reducing input costs for cover crop seed. Chapter 2 focused on interseeding mixtures of WCR and crimson clover, where we hypothesized that residual rates would marginally impact percent cover of WCR and crimson clover mixtures. Our results indicated, in chapter one, that reducing seeding rate by using STCR planting method did indeed drive seed cost savings while improving yield and EORN in comparison to a traditionally planted cover crop. Our results in chapter 3 also indicated reduced seeding rates found in novel planting methods improved the on-farm economics of using cover crops while maintaining healthy soybean yields. Lower-than-average rainfall accumulations later in the growing season coupled with cover crop residues likely influenced soil moisture retention, benefiting the cash crop during the dry spell, helping maintain yields. Interseeding methods, as studied in chapter 2, did not show any significant impact on corn grain yield or yield components. Subsequently, half- and full-rate residual herbicides did not impact percent cover of cover crops. However, use of residual herbicides should be consistent with all herbicide labels and laws, and producers should use label-recommended amounts to maintain maximum efficacy of herbicides and to prevent resistant weed populations. Also, interseeded cover crops failed to successfully establish, resulting in minimal cover crop biomass in later sampling dates.