Physiological Maturity Stage Research Articles

Effects of Harvesting Times and Germplasm Accessions on the Physical Properties of Roselle (Hibiscus sabdariffa L.) Seeds

Roselle (Hibiscus sabdariffa L.) is an important crop grown successfully in tropical and subtropical climates with huge nutritional, economic, and industrial benefits. The physical properties of seeds, particularly length, width, thickness, mean diameter, angle of repose, degree of sphericity, mass, and surface area, have been found to play significant roles in designing equipment for storage, transportation, and subsequent field operations of the seeds. Therefore, a study was carried out to determine the effects of different harvesting times on the physical properties of seeds of twelve roselle accessions for their subsequent industrial management. In total, 12 × 3 factorial arrangements in Randomized Complete Block Design and Completely Randomized Design were used for the field and laboratory experiments, respectively. The first factor was germplasm accessions at twelve levels (HS08, HS11, HS19, HS25, HS27, HS32, HS41, HS58, HS59, HS69, HS83, and H86), and the second factor was harvesting times at three levels (physiological maturity, one week after physiological maturity, and two weeks after physiological maturity). Seeds of accession HS32 harvested at the physiological maturity stage had the highest moisture content, which was similar to the other 11 accessions harvested at the same stage. The seeds of accession HS08 harvested at physiological maturity had significantly the best values in seed length (4.33 mm), seed width (4.30 mm), seed thickness (2.43 mm), seed geometric mean diameter (3.83 mm), seed angle of repose (20.57°), seed sphericity (0.76), seed surface area (18.57 mm2), and seed mass (0.05 g). Further, there were strongly positive and significant correlations between seed width and seed angle of repose (r = 0.93); seed width and seed length (r = 0.84); seed width and mean seed diameter (r = 0.89); seed width and seed sphericity (r = 0.68); seed width and seed surface area (0.94). There were also strongly positive and significant correlations between seed thickness and seed sphericity (r = 0.79) and also between seed thickness and seed surface area (r = 0.63). In conclusion, the physical properties of accession HS08 harvested at the physiological maturity stage could be very important in designing machinery for roselle seeds storage, transportation, and subsequent field operations.

Yield and growth characteristics of a high oil–protein soybean with enhanced diacylglycerol acyltransferase

AbstractIntroduction of the VgDGAT1A gene in soybean [Glycine max (L.) Merr.] genotypes increased both protein and oil content and resulted in earlier maturation compared with commonly cultivated soybean genotypes (i.e., Jack). However, the effect of VgDGAT1A gene on the length of the vegetative, reproductive, and the overall growth period of soybean has not been thoroughly evaluated. A randomized complete block design consisting of two transgenic soybean genotypes with VgD1‐1 and VgD1‐2 highly active acyl‐CoA: diacylglycerol acyltransferase (DGAT) from ironweed [Vernonia galamensis (Cass) Less.] and nontransgenic control (Jack) was evaluated in field studies in 2015 and 2016 in Lexington, Kentucky. Levels of sucrose accumulation and seed weight were calculated for the three genotypes. Soybean grain yield, seed weight, and seed number were similar among all genotypes in both years. Modified genotypes reached the R7 (beginning of physiological maturity) stage earlier, and the rate of dry weight accumulation in individual seeds ranged between 2.8 to 4.4 mg seed−1 day−1 and was not different in comparison with the control (range: 3.4–4.7 mg seed−1 day−1). While days to reach R7 was shorter in VgD, there were no differences among genotypes for pod weight (PW), seed weight (SW), pod sucrose (PS), or seed sucrose (SS) concentrations. Linear plateau and cubic models were the best fit for seed weight for both years. These results indicated that despite earlier maturation in VgD genotypes, seed growth, and final soybean yield were similar among VgD and Jack.

Predicting field N2O emissions from crop residues based on their biochemical composition: A meta-analytical approach

Crop residue incorporation is a common practice to increase or restore organic matter stocks in agricultural soils. However, this practice often increases emissions of the powerful greenhouse gas nitrous oxide (N2O). Previous meta-analyses have linked various biochemical properties of crop residues to N2O emissions, but the relationships between these properties have been overlooked, hampering our ability to predict N2O emissions from specific residues. Here we combine comprehensive databases for N2O emissions from crop residues and crop residue biochemical characteristics with a random-meta-forest approach, to develop a predictive framework of crop residue effects on N2O emissions. On average, crop residue incorporation increased soil N2O emissions by 43% compared to residue removal, however crop residues led to both increases and reductions in N2O emissions. Crop residue effects on N2O emissions were best predicted by easily degradable fractions (i.e. water soluble carbon, soluble Van Soest fraction (NDS)), structural fractions and N returned with crop residues. The relationship between these biochemical properties and N2O emissions differed widely in terms of form and direction. However, due to the strong correlations among these properties, we were able to develop a simplified classification for crop residues based on the stage of physiological maturity of the plant at which the residue was generated. This maturity criteria provided the most robust and yet simple approach to categorize crop residues according to their potential to regulate N2O emissions. Immature residues (high water soluble carbon, soluble NDS and total N concentration, low relative cellulose, hemicellulose, lignin fractions, and low C:N ratio) strongly stimulated N2O emissions, whereas mature residues with opposite characteristics had marginal effects on N2O. The most important crop types belonging to the immature residue group – cover crops, grasslands and vegetables – are important for the delivery of multiple ecosystem services. Thus, these residues should be managed properly to avoid their potentially high N2O emissions.

Dry Matter Production and Nitrogen Uptake as Influenced by Irrigation and Nitrogen Levels in Maize

A field experiment was conducted at Agro Climate Research Center, Agricultural Research Institute, P.J.T.S Agricultural University, Rajendranagar, Hyderabad, India during rabi 2019-20. The field experiment was laid out in a split plot design with three replications. The treatments comprising of three irrigation scheduling based on (Depletion of Available Soil Moisture) at 60% DASM, 40% DASM and 20% DASM as main plots and three nitrogen levels viz., 90, 180 and 240 kg N ha-1 as sub-plots. The experiment was laid out in split plot design. The results indicated that, among the different treatment combinations, the crop irrigation scheduled at 20 % DASM in conjunction with 240 kg N ha-1 accumulated significantly more dry matter of 34.2 g, 149.2 g, 233.7 g and 284.8 g plant-1, at 6th leaf, silking, dough and physiological maturity stages, respectively. The nitrogen uptake was found to be more when the crop was irrigated at 20 % DASM in conjunction with 240 kg N ha-1 (67.1 g, 231.8 g, 294.7 g and 305.3 g plant-1) at 6th leaf, silking, dough and physiological maturity stages, respectively.

Warming changed seasonal water uptake patterns of summer maize

Warming affects tremendously agricultural water cycle though crop evapotranspiration, soil evaporation, crop water uptake pattern etc. Crop water uptake pattern plays an important role on water cycle of the groundwater-soil-plant-atmosphere continuum (GSPAC). A comprehensive assessment of climatic factors, water sources supply dynamics and crop seasonal water uptake pattern under warming is lacking. Here, climatic factors, water sources supply dynamics during the whole growing stages for summer maize under warming 2 ℃ were monitored by a Water Transformation Dynamical Processes Experimental Device (WTDPED). Isotopic labeling experiments by deuterium oxide (2H2O) were conducted to determine seasonal variations in crop water uptake patterns. The contributions of soil water at different depths to water uptake were quantified by the MixSIAR Bayesian mixing model and dual stable isotopes (δD and δ18O). Results showed that warming enriched the δD values in topsoil (10–20 cm) and depleted the δD values in deep soil (80–270 cm). Warming increased the proportional contributions of soil water at 0–40 cm layer to maize crop uptake by 3.5%, 19.9%, 5.3%, 14.4% and 29.8% during transplanting to maturation stage compared with ambient temperature. It means that deficit irrigation is better applied to reduce root biomass accumulation in the superficial soil layer (0–40 cm) especially at sixth leaf to 12th leaf stage and milk to physiological maturity stage for maize. To some extent, the reduced water infiltration in soil profile offset the increased soil evaporation at 0–80 cm layer under warming. Simultaneously, the maize water uptake for shallow soil layers was greatly induced due to the decrease acclimation of vapor pressure deficit (VPD) especially during tasseling-silking to maturation stage. Smaller water supply and more irrigation times were required for adapting warming condition for summer maize, particularly in water-limited regions. The study gives new perspectives of the effect mechanisms for crop water utilization and agricultural water cycles under future climate change.

Response of nitrogen and potassium fertilization on the growth performance of aromatic Boro rice

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, during December 2017 to May 2018 to study growth performance of aromatic Boro rice (cv. BRRI dhan50) in response to nitrogen and potassium fertilization. The experiment consisted of four levels of nitrogen viz., 0, 50, 100 and 150 kg ha-1, and four levels of potassium viz., 0, 30, 60 and 90 kg ha-1. The experiment was laid out in a randomized complete block design with three replications. The results revealed that nitrogen and potassium fertilization and their interaction exerted significant influence on growth performance of BRRI dhan50. Application of 100 kg N ha-1 produced the tallest plant (82.17 cm), the highest number of tillers hill-1 (10.08) and chlorophyll content (52.21) at heading stage. While, application of 90 kg K ha-1 produced the tallest plant (81.44 cm) at physiological maturity stage, the highest number of tillers hill-1 (9.66) and chlorophyll content (51.54) at heading stage. In case of interaction, the tallest plant (85.33 cm), the highest number of tillers hill-1 (10.83) and chlorophyll content (58.28) were obtained from 100 kg N ha-1 along with 90 kg K ha-1 at heading stage. Therefore, application of 100 kg N ha-1 along with 90 kg K ha-1 interaction appeared as the promising practice in aromatic rice (cv. BRRI dhan50) cultivation in terms of growth performance.

Responses of maize hybrids with contrasting maturity to planting date in Northeast China

Maize sowing in semi-humid region of Jilin province is often delayed beyond the optimum planting time window because of soil water stress typically occurring before or during the planting season. Research was conducted at Lishu city, in Jilin province from 2009 through 2010 to determine the responses of maize hybrids with contrasting maturity to planting date. Three popular hybrids with contrasting different maturity, short-season hybrid Jidan27, mid-season hybrid Xianyu335, and full-season hybrid Zhengdan958 were planted in early May and mid-May and thinned to populations of 67,500 plants ha−1. The results showed that durations from emergence to silking stage for all the hybrids consistently shortened as the planting delayed, but interaction effects of hybrids, planting date and year existed for the duration of silking to physiological maturity stage. The longer maturity hybrid usually had grain yield advantage over earlier maturity hybrid when planting at early May, but the earlier maturity hybrid often showed a greater yield than longer maturity hybrid when planting was delayed. The highest yield occurred at the treatment combination of the mid-season hybrid and delayed planting date, and the shorter season hybrid typically showed stable and higher grain yield across planting dates. Changes in grain volume per unit of land area among hybrids and planting date treatment combination were consistent with the changes in grain yields, indicating that the yield is determined usually by the sink capacity. Further research is needed to evaluate the effects of hybrids maturity and planting date on maize under different planting densities.

Growth Rate, Dry Matter Accumulation, and Partitioning in Soybean (Glycine max L.) in Response to Defoliation under High-Rainfall Conditions.

The frequency of heavy rains is increasing with climate change in regions that already have high annual rainfall (i.e., Sichuan, China). Crop response under such high-rainfall conditions is to increase dry matter investment in vegetative parts rather than reproductive parts. In the case of soybean, leaf redundancy prevails, which reduces the light transmittance and seed yield. However, moderate defoliation of soybean canopy could reduce leaf redundancy and improve soybean yield, especially under high-rainfall conditions. Therefore, the effects of three defoliation treatments (T1, 15%; T2, 30%; and T3, 45% defoliation from the top of the soybean canopy; defoliation treatments were applied at the pod initiation stage of soybean) on the growth and yield parameters of soybean were evaluated through field experiments in the summer of 2017, 2018, and 2019. All results were compared with nondefoliated soybean plants (CK) under high-rainfall conditions. Compared with CK, treatment T1 significantly (p < 0. 05) improved the light transmittance and photosynthetic rate of soybean. Consequently, the leaf greenness was enhanced by 22%, which delayed the leaf senescence by 13% at physiological maturity. Besides, compared to CK, soybean plants achieved the highest values of crop growth rate in T1, which increased the total dry matter accumulation (by 6%) and its translocation to vegetative parts (by 4%) and reproductive parts (by 8%) at physiological maturity. This improved soybean growth and dry matter partitioning to reproductive parts in T1 enhanced the pod number (by 23%, from 823.8 m−2 in CK to 1012.7 m−2 in T1) and seed number (by 11%, from 1181.4 m−2 in CK to 1311.7 m−2 in T1), whereas the heavy defoliation treatments considerably decreased all measured growth and yield parameters. On average, treatment T1 increased soybean seed yield by 9% (from 2120.2 kg ha−1 in CK to 2318.2 kg ha−1 in T1), while T2 and T3 decreased soybean seed yield by 19% and 33%, respectively, compared to CK. Overall, these findings indicate that the optimum defoliation, i.e., T1 (15% defoliation), can decrease leaf redundancy and increase seed yield by reducing the adverse effects of mutual shading and increasing the dry matter translocation to reproductive parts than vegetative parts in soybean, especially under high-rainfall conditions. Future studies are needed to understand the internal signaling and the molecular mechanism controlling and regulating dry matter production and partitioning in soybean, especially from the pod initiation stage to the physiological maturity stage.

Desiccation of corn allows earlier direct seeding of winter camelina in the northern Corn Belt

AbstractIn the U.S. Upper Midwest where growing seasons are short, establishing winter annual cover crops following corn (Zea mays L.) is challenging. Winter camelina [Camelina sativa (L.) Crantz] shows promise as a winter annual cover crop that can be dual cropped with soybean [Glycine max (L.) Merr.] to help diversify the corn–soybean rotation. This 2‐yr field study in southern and western Minnesota evaluated desiccating corn with a preharvest aid to hasten its dry‐down and hence harvest so that camelina could be no‐till drilled in a timely manner. We hypothesized that direct drilling camelina following corn harvest would improve establishment and yields. Sodium chlorate was applied as a desiccant to corn at early (D1) and mid‐R5 (D2) and physiological maturity (D3) stages of development, including an untreated check. The D1 and D2 treatments hastened corn harvest by 1 to 3 wk compared with the check. Corn grain yields were unaffected by the D2 and D3 treatments, but significantly declined by 16% in D1. Camelina seed yield did not differ among desiccation treatments and averaged 815 kg ha−1 across both locations with an average oil content of 385 g ka−1. Desiccating corn hastened its harvest allowing more time to drill‐seed camelina, thus improving establishment. However, more work is needed to improve management and genetics of winter camelina for use as a cash cover crop in corn systems.

Cultivation of maize in different environments and their effects on agronomic traits

The objective of this work was to show which traits are influenced by the interaction genotype x irrigated environment, to reveal trends of linear associations in each environment and to identify genotypic variation through canonical variable analysis in maize. The experiment was conducted in Campos Borges – RS. The experimental design used was randomized blocks organized in a factorial scheme, being two cultivation environment (dry environment characterized only by the availability of rainwater; irrigated environment where a 15 mm layer of water was applied ten days apart the crop cycle, from seedling emergence to physiological maturity stage) x 13 hybrids of maize, arranged in three replicates. The traits plant height, insertion of ear height, mass of one thousand grains and grains yield are influenced by the genotypes x environments interaction. The irrigated environment presents superiority in relation to dry environment for all the traits studied. In general, the genotype G9 performs better than others. The irrigated environment presents superiority than dry environment, in relation to the traits plant height, insertion of ear height, mass of one thousand grains, grain yield per hectare, ear length, ear diameter, ear mass, grains mass per ear and number of grains per ear row.

Growth, Yield and Shattering Dynamics of Seeds of Twelve Roselle (Hibiscus sabdariffa L.) Accessions

Roselle (Hibiscus sabdariffa L.) is an important crop grown in tropical and subtropical climates with huge nutritional, economic and industrial benefits. The plant undergoes explosive shattering to disperse seeds after physiological maturity leading to high loss of seeds at the time of harvesting. A field experiment was carried out to determine the effect of different harvesting stages on the growth, yield and shattering dynamics of seeds of twelve Roselle accessions in the Department of Horticulture, Kwame Nkrumah University of Science and Technology, Kumasi from March to November, 2019. A 3x12 factorial design in Randomized Complete Block Design (RCBD) was used for the study, where factor one was harvesting stages at three levels (physiological maturity, one week after physiological maturity and two weeks after physiological maturity) and factor two was accessions at twelve levels. The study revealed that accession HS08 performed best in terms of growth (plant height, the number of leaves, number of branches and stem girth) and reproductive parameters (number of days to flowering) and accessions HS27 and HS08 produced the highest yield (number of pods, number of seeds per pod, and total seed yield). Harvesting of seeds at the physiological maturity stage happened to be the ideal time because seeds were harvested safely without any losses (0%) due to shattering as compared to the other harvesting stages. The study also established a very strong, positive and significant relationship between seed yield and number of leaves (r=0.7093) and the number of branches (r=0.9241). However, there was a strong but negative and significant relationship between seed yield and percentage seed shattering loss (r=-0.9633). There was a very strong, positive and significant relationship between number of leaves and stem girth (r=0.7769). The number of seeds per plant correlated positively with the number of pods (r=0.7358). A regression model which was given by the equation; Y (Seed yield)=670.96-0.3152 (Shattering loss), R2=0.9279, p&lt;0.0000, indicated that shattering loss significantly affected seed yield to an extent that it contributed 93% of the variation in the seed yield.

Comparative Studies on the Fruit Yield of two Capsicum Varieties at Physiological Maturity

A study was carried out at the Busia Agricultural Training Center (A.T.C), Western Kenya in 2019 to compare the fruit yields of two capsicum varieties from Syngenta seed company at the physiological maturity stages of red and yellow colors. Commandant F1 (red) and Admiral F1 (yellow) capsicum varieties were established under greenhouse conditions in two experimental beds measuring 0.7m by 13.5m. No controls were planted. Drip irrigation system was used with a plant-to-plant and inter-row spacing of 30cm and 40cm, respectively. Both of the two varieties were planted at the same time and subjected the same fertilizer treatments, pest and disease control measures, cultural practices and moisture supply. Data was collected on growth parameters (number of vegetative branches, flower buds and flowers) and yield components (number of fruits and harvest weight). Independent sample t-test was used to compare parameters (number of flowers, flower buds, fruits and the number of branches) for the two colored capsicum varieties, at a probability of p≤0.05. Further analysis involved finding weight and harvest averages for the two varieties. All analyses were performed in IBM SPSS Statistics, version 23. The red-coloured variety produced an average of 9.36 buds per plant compared to 5.2 for the yellow cultivar (p=0.01). Significant differences in the average yield potential of the yellow and red varieties (calculated as flowers, buds, and young fruits) were found between the red and yellow varieties (p=0.02). The red variety had a higher yield potential (19.52) than the yellow one (13.46). Within-variety weight comparison showed that the yellow variety lost a significant amount of fruit mass between the second and third harvest (0.122kg or 61%) compared to the red variety which lost 0.099kg or 58%. Keywords: Capsicum; Fruit yield; Physiological maturity; Variety; Red; Yellow

Impact of glyphosate applied preharvest on oat kernel quality

AbstractBackground and objectivesPreharvest glyphosate is applied to oats for weed control and as a desiccant. The effect of glyphosate applied at various stages of oat physiological maturity on oat end product quality has not been reported previously. In this study, the effects of glyphosate application at two separate stages of physiological maturity on oat groat quality and rolled oats quality were determined.FindingsOat was grown at two locations. Glyphosate was applied at the soft dough, physiological maturity stages, or not applied. Effect of preharvest glyphosate application at the oat soft dough stage on groat hardness, groat percentage (0.7%–3.7% decrease by cultivar), and percent plump groats (0.3%–6.1% decrease by cultivar), when compared to untreated oats, was noticeable. However, glyphosate applied at physiological maturity (manufacturer's recommendation) did not detrimentally affect groat starch (average 60.3%) or end product quality.ConclusionsTherefore, from an end‐user perspective, applying glyphosate preharvest at oat physiological maturity does not impact oat quality.Significance and noveltyGlyphosate when applied preharvest to oats can control weed and facilitate harvest, a boon to farmers. Final oat quality, a decisive factor for commercial processor use, was not detrimentally affected when glyphosate was applied at oat physiological maturity.

Physiological Features of the Reproductive System of Female Nutria

This article provides information about a promising alternative field of animal husbandry – nutria breeding. This involves the production of fur and high-quality meat products, which contain a large amount of nitrogenous extractives and muscle hemoglobin. This study examined the sexual system of female nutria, and the dynamics, duration and features of each stage of the female nutria’s sexual cycle, including estrus, sexual arousal, hunting, braking and phase balancing. The methods of observation, clinical examination, research of smears and fingerprints, and analysis of the cytogram of the vaginal epithelium at different stages of sexual and physiological maturity of female nutria were used. When analyzing the cytogram of the vaginal epithelium, the structure, color, and percentage of basal, parabasal, superficial, and keratinized cells were indicated. Information about the timing of sexual and physiological maturity, their features, processes and signs of manifestation, and different timing of sexual and physiological maturity in summer and winter is provided.&#x0D; Keywords: nutria, female, puberty, physiological maturity

Dry matter partitioning, yield and grain protein content of fine aromatic boro rice (cv. BRRI dhan50) in response to nitrogen and potassium fertilization

An experiment was conducted to study dry matter partitioning, yield and grain protein content of fine aromatic Boro rice (cv. BRRI dhan50) in response to nitrogen and potassium fertilization. The experiment consisted of four levels of nitrogen viz., 0, 50, 100 and 150 kg/ha and four levels of potassium viz., 0, 30, 60 and 90 kg/ha. The results revealed that at growth stage, the highest total dry matter partitioning and accumulation were obtained from 150 kg N/ha along with 90 kg K/ha at physiological maturity stage. At harvest, the highest number of tillers/hill (8.58), number of grains/panicle (113.9), grain yield (5.15 t/ha) and grain protein content (8.30%) were obtained from 100 kg N/ha along with 90 kg K/ha. Total dry matter partitioning and accumulation were greatly influenced by the application of 150 kg N/ha along with 90 kg K/ha. Application of 100 kg N/ha along with 90 kg K/ha interaction appeared as the promising practice in fine aromatic rice (cv. BRRI dhan50) cultivation in terms of yield and grain protein content.

Winter Crop Growth Monitoring using Multi-Temporal NDVI Profiles in Kapadvanj Taluka, Gujarat State

In the present study on winter crop growth monitoring in different villages in Kapadvanj Taluka of Kheda district was carried out using multi-temporal Sentinel-2 multi-spectral data (spatial resolution 10-m). Multi-temporal Sentinel-2 data covering study area for the winter crop period from November-2018 to March-2019 was downloaded from https://earthexplorer.usgs.gov/. The major objective of this study was to monitor site-specific crop growth in different villages of Kapadvanj Taluka by generating Normalized Difference Vegetation Index (NDVI) profiles of major winter crops. The spectral behavior of wheat, potato, bajara and castor crops during active growth stages was studied and it was observed that the spectral response of wheat and potato crops have quite distinct spectral behavior. However, castor and bajara crops do not show distinct spectral behavior. In this study, from the NDVI profiles of different crops it was observed that very distinct growth stages like early growth stage to flag leaf emergence which correspondence to rising of NDVI, followed by flag leaf emergence to flowering and grain filling stages which corresponds to maximum NDVI and finally physiological maturity stages corresponding to declining of NDVI of all the winter crops.

Leaf nitrogen and phosphorus resorption improves wheat grain yield in rotation with legume crops in south-eastern Australia

Nutrient resorption from senescing leaves to grain at physiological mature stage is critical to recover nutrients and improve grain production in semi-arid environment in south-eastern Australia. The aim of this study is to examine nitrogen (N) and phosphorus (P) resorption patterns and their effects on grain yield and quality of wheat in rotation with legume crops. A range of legume crops were grown in the field followed by one and two wheat crops in contrast with continuous wheat and canola crops with N fertiliser over 3 years. The soil N and P availability, flag leaf N and P nutrient status and resorption were measured in the first and second wheat crops after legume crops. Including legume crops in crop rotation increased soil available N concentration. Green leaf N concentration, and senesced leaf N and P concentrations increased as soil available N increased. However, N resorption efficiency (NRE) and P resorption efficiency (PRE) decreased as soil available N concentration increased. The NRE and PRE were positive correlated to grain yield and 1000-grain weight, but negative correlated to grain protein. The soil N benefit from legume crops can last more than one growing season. Under moisture stress conditions increased grain yield was associated with improved nutrient resorption efficiency via increased grain size regardless soil nutrient availability.

Épocas de aplicação de azoxistrobina + mancozebe no controle de mancha branca do milho

Um dos principais métodos de controle da mancha branca do milho, o controle químico com estrobilurinas e fungicidas protetores demonstraram efeito no controle da doença, no entanto, condicionada ao momento de sua realização em estádios fenológicos da cultura. O objetivo deste trabalho foi avaliar o controle e efeito no progresso temporal da mancha branca do milho com a associação dos fungicidas mancozebe e azoxistrobina em diferentes épocas de aplicação, dois cultivares, duas localidades de plantio e o efeito na produtividade da cultura. Os experimentos foram conduzidos nos municípios de Marechal Cândido Rondon e Sertanópolis, PR. Foram utilizados dois híbridos suscetíveis, DKB230PRO3 e DKB290PRO3. O delineamento experimental utilizado foi de blocos casualizados com 4 repetições. As avaliações foram efetuadas 10 dias após cada aplicação, além de uma avaliação no estádio de maturidade fisiológica. A severidade da doença foi avaliada através da quantificação da área foliar lesionada em 10 plantas por parcela e utilizadas no cálculo da Área Abaixo da Curva de Progresso da Doença, submetidos a análise de variância e o teste de médias. As curvas de progresso da doença foram ajustadas aos modelos logístico e exponencial. A produtividade foi estimada após a colheita manual, com o peso de mil grãos e produtividade (kg ha-1). Aplicações dos fungicidas em estádios V8 e V4+V8+VT proporcionaram melhor controle da mancha branca. Aplicações no estádio V4 não proporcionaram severidades diferentes da testemunha sem aplicação. Não foram observados ganhos significativos em produtividade em função da aplicação dos fungicidas.

Timing of harvesting reverses the effect of cutting twice with ratoon rice

A new ratoon rice cropping method known as the SALIBU system, which uses the lower nodes of the stubble, is gradually spreading throughout the tropical regions. In a previous study, the technology package, ‘cutting twice’ has a large effect on the number of ratoons (tillers), and interestingly, the effect has a large positive effect under poor management conditions, but a medium negative effect under standard management conditions. The conditions included fertilizing, water management, and growth stage at harvesting; however, which of these conditions has the greatest effect on the effect of ‘cutting twice’ remains unclear. We performed a pot experiment focusing on fertilizer and timing of harvesting, to clarify which of the level of fertilizer or the delay of harvesting time affects the number of ratoons. The results showed that with a short delay in harvesting there were almost no ratoons, a long delay in harvesting resulted in many ratoons. This indicates the negative effect of cutting twice occur due to earlier harvesting. Generally, the growth of ratoons depends on the carbohydrate reserves of the stubble. Hence, in the case of a single harvest, the ratoons decrease with the delay in harvesting. On the other hand, cutting the stem increases dead buds in the nodes closer to the ground. Namely, the second cut will remove the high node buds and reduce the incidence of ratoons. As for adding fertilizer results in more ratoons steadily. Harvesting earlier (at the physiological maturation stage; 25% green husk) than normal is emphasized in the SALIBU technology package. However, our results show the ‘cutting twice’ reduces the number of ratoons when harvesting early.

New epiphytic strains of lactic acid bacteria improve the conservation of corn silage harvested at late maturity

We evaluated fifty-three strains of lactic acid bacteria (LAB) isolated from corn silages from different farms for use as inoculants in corn silages. Bacteria were characterized for growth and pH reduction in corn extract, growth at different temperatures and the ability to inhibit the growth of silage-spoilage microorganisms. The strains CCMA1362, 1363 and 1364 (Lactobacillus farraginis), CCMA1365 (L. plantarum), CCMA1366 (L. buchneri), and CCMA1367 (Pediococcus acidilactici) isolated from corn silage and CCMA170 strain (L. hilgardii) isolated from sugarcane showed good results in laboratory evaluation (good growth and reduction of pH in corn extract; good growth at different temperature and ability to inhibit silage-spoilage microorganisms). These strains were selected and evaluated in corn silages harvested at an advanced stage of physiological maturity (454 g/kg DM). Experimental silos were opened after 10, 32 and 100 days of storage. Crude protein, ash and starch contents were not affected by the inoculation or storage time. Inoculation with the obligate homofermentative strain CCMA 1367 (P. acidilactici) resulted in silages with the greatest DM loss and the lowest aerobic stability. Silages treated with the obligate heterofermentative strains (L. buchneri, L. hilgardii and L. farraginis) had the lowest DM loss, highest aerobic stability, good acid production and pH value, and lowest numbers of yeasts. The species L. farraginis is reported for the first time in studies with corn silage and in particular the CCMA1362 (L. farraginis) strain was effective in lowering DM loss and reducing the numbers of yeasts throughout the ensiling period. Our results are important because they show that silage conservation can be improved even in late maturity corn silage when treated with select lactic acid bacteria L. farraginis CCMA1362. More studies are needed to evaluate the efficiency of these strains under field conditions.