Consecutive Years Of Application Research Articles

Effects of Different Proportions of Organic Fertilizer Replacing Chemical Fertilizer on Soil Nutrients and Fertilizer Utilization in Gray Desert Soil

Organic fertilizer can improve soil management and alleviate soil nutrient loss caused by excessive fertilization. This study determines a fertilization scheme that can achieve high and stable crop yield and effective soil fertilization by exploring the effects of different organic fertilizer proportions on soil nutrient content, fertilizer utilization rate, and wheat yield. The experiment was conducted from 2018 to 2020 using the Xinchun 38 wheat variety and gray desert soil. The experiment used six treatments: no fertilizer (CK), with normal nitrogen and phosphorus fertilizer (CF). The amount of conventional chemical nitrogen fertilizer was reduced by 6%, 12%, 18%, and 24%, respectively, and supplemented with organic nitrogen fertilizer of the same proportion. The experimental treatment codes were SF6, SF12, SF18, and SF24, respectively. Plant samples from six wheat growth stages and 0–20 cm soil samples were collected to analyze the nitrogen and phosphorus content and organic matter; dry matter accumulation, crop yield, and yield components were measured at the harvest stage. Soil available nitrogen, phosphorus, potassium, and soil organic matter contents increased with the replacement ratio of organic fertilizer after three consecutive years of application. The available nutrients and organic matter in soil treated with SF18 and SF24 were significantly higher than those in CK and CF. The dry matter accumulation and nutrient accumulation of wheat increased with increasing organic fertilizer replacement rates of SF18 and SF24, respectively. Nitrogen and phosphorus fertilizer utilization rates, partial productivity, and agricultural use efficiency also increased, with the SF18 and SF24 treatments having higher organic fertilizer replacement rates than those in the other treatments. The number of ears, 1000-grain weight, and yield of wheat treated with SF18 treatment produced the best results. Therefore, continuously using organic fertilizer as a partial replacement for conventional fertilizer can increase wheat growth and soil nutrient availability, which can improve the utilization rate of fertilizer, thereby achieving stability and even a significant increase in yield.

Long-Term Increases in Continuous Cotton Yield and Soil Fertility following the Application of Cotton Straw and Organic Manure

Long-term continuous cotton cropping results in a significant decrease in soil quality and soil organic carbon, threatening cotton yield. The application of organic amendments is considered an effective management practice for the sustainability of soil productivity and often increases yield. However, the sustainable improvement in the cotton yield, stability, and soil fertility over time resulting from organic amendments with cotton straw and organic manure still need to be confirmed with research, especially under a continuous cotton cropping system. This study evaluated the effect of 12 years of consecutive application of cotton straw and organic manure on continuous cotton yield, soil quality, and soil organic carbon. Four treatments, i.e., chemical N and P fertilizers (NP, control), NP plus cotton straw (NPS), NP plus manure (NPM), and NP plus cotton straw and manure (NPSM), were carried out. The results indicated that the addition of cotton straw and organic manure improved the temporal stability and sustainability of cotton yield. The combination of cotton straw and organic manure resulted in the greatest improvement, increasing the average annual cotton yield by 32.28% compared with the control (NP). A correlation analysis revealed that cotton yield was closely related to soil quality and soil organic carbon. The application of cotton straw and organic manure increased cotton yield by enhancing soil fertility, especially the quantity and quality of soil organic carbon, which improved the supply and cycling of soil nutrients and benefited the stability and sustainability of the cotton yield. Reusing cotton straw and organic manure could improve the sustainable productivity of cotton soil and provide additional environmental value as well as having great potential for cleaner and sustainable cotton production.

Biochar derived from papermill factories improves soil physical and hydraulic properties in no-till cotton fields

Whether biochar produced as a by-product of energy generation from the papermill industry, and often disposed in landfills, can be gainfully applied to commercial croplands has not been investigated. The objective of this study was to investigate the physical and hydraulic properties of soils in commercial cotton fields managed as no-till systems following repeated applications of biochar generated as a waste of a papermill plant. Undisturbed cores and disturbed soil samples were collected from 0–5 and 5–10 cm layers from five commercial no-till fields in Mississippi, USA that received 6.7 Mg ha−1 year−1 biochar for 0, 2, 3, 5 or 10 years. A number of physical, hydraulic, and chemical properties of these samples were measured in the lab. The results showed that biochar reduced the degree of soil compactness and increased soil aggregation and structural stability index. The findings were particularly apparent for the 10 years of consecutive application, which increased soil aggregate stability by up to 67%, reduced bulk density from 1.40 to 1.26 g cm−3, and reduced degree of compactness from 73.2% to 62.8%. Biochar increased soil porosity but much of this increase (55%) occurred for small pores (< 0.5 μm) with little effect on storage pores (0.5–50 μm) or transmission pores (> 50 μm). Consequently, biochar increased soil field capacity by up to 26%, but PAW increased by only 17%. Biochar significantly increased soil physical quality index score in the 0–5 cm layer from 0.16 to 0.26 and the increase was positively correlated with the number of years of application. The results suggest biochar generated as a byproduct of papermill could be land-applied in real-world crop production systems to improve soil health as an alternative to disposal in landfills.Graphical

&lt;b&gt;Chromium accumulation in maize and cowpea after successive applications of composted tannery sludge

Chromium (Cr) accumulation in soil and plants has been reported after successive applications of tannery sludge, which is a matter of concern because Cr can promote environmental contamination and affect the food chain. In this study, we evaluated the growth of and Cr accumulation in maize and cowpea after seven years of consecutive applications of composted tannery sludge (CTS) under field conditions. The experiment consisted of application of CTS at five levels: 0 (control), 2.5, 5, 10, and 20 Mg ha -1 (dry basis). The growth of and Cr accumulation in maize and cowpea were evaluated at 75 and 65 days after plant emergence, respectively. CTS application increased the shoot biomass of maize and cowpea. Accumulation of Cr was similar for both plant species, with higher accumulation in roots. However, Cr accumulation in grains differed as the CTS doses increased; cowpea accumulated more Cr while maize did not accumulate more Cr in grains with higher CTS doses. In conclusion, application of CTS led to higher growth of maize and cowpea plants, and both species exhibited similar Cr accumulation in roots and shoots.

Recycling organic wastes to agricultural land as a way to improve its quality: A field study to evaluate benefits and risks

A field study was established to assess the effects of a sewage sludge (SS), a mixed municipal solid waste compost (MMSWC) and a compost produced from agricultural wastes (AWC), in a Vertisol, using Lolium multiflorum L. The amendments were applied for two consecutive years: 6, 12 and 24t dry matter ha−1 for SS, and the amendment doses for MMSWC and AWC were calculated to deliver the same amount of organic matter (OM) per unit area. The amendments had significant beneficial effects on some soil properties (e.g. soil OM, NKjeldahl, extractable P and K), and on plant productivity parameters (e.g. biomass yield, chlorophyll, foliar area). For instance, soil OM increased from 0.78% to 1.71, 2.48 and 2.51%, after two consecutive years of application of 24t dry matter ha−1 of SS, MMSWC and AWC, respectively, while the plant biomass obtained increased from 7.75tha−1 to 152.41, 78.14 and 29.26tha−1, for the same amendments. On the plant, effects were more pronounced for SS than for both compost applications, a consequence of its higher capacity to provide N to the plant in a readily available form. However, after two years of application, the effects on soil properties were more noticeable for both composts, as their OM is more resistant to mineralization, which endures their beneficial effects on soil. Cadmium, Cr, Ni and Pb pseudo-total concentrations, were not affected significantly by the application of the organic wastes to soil, in all tested doses, neither their extractability by 0.01M CaCl2. On the contrary, Cu and Zn pseudo-total concentrations increased significantly in the second year of the experiment, following the application of the higher rate of MMSWC and AWC, although their extractability remained very low (<0.5% of their pseudo-total fraction). Trace elements concentrations in the aboveground plant material were lower than their maximum tolerable levels for cattle, used as an indicator of risk of their entry into the human food chain. Despite these results, it is interesting to note that the SS promoted a significant increase in the foliar concentrations of Cu, Ni and Zn that did not happen in composts application, which can be explained by the reduction of the soil pH, as a consequence of SS degradation in soil. Concluding, if this type of organic wastes were to be used in a single application, the rate could be as high as 12 or even 24tha−1, however, if they are to be applied in an annual basis, the application rates should be lowered to assure their safe application (e.g. to 6tha−1). Moreover, it is advisable to use more stable and mature organic wastes, which have longer lasting positive effects on soil characteristics.

Biochar Improves Soil Aggregate Stability and Water Availability in a Mollisol after Three Years of Field Application.

A field experiment was carried out to evaluate the effect of organic amendments on soil organic carbon, total nitrogen, bulk density, aggregate stability, field capacity and plant available water in a representative Chinese Mollisol. Four treatments were as follows: no fertilization (CK), application of inorganic fertilizer (NPK), combined application of inorganic fertilizer with maize straw (NPK+S) and addition of biochar with inorganic fertilizer (NPK+B). Our results showed that after three consecutive years of application, the values of soil bulk density were significantly lower in both organic amendment-treated plots than in unamended (CK and NPK) plots. Compared with NPK, NPK+B more effectively increased the contents of soil organic carbon, improved the relative proportion of soil macro-aggregates and mean weight diameter, and enhanced field capacity as well as plant available water. Organic amendments had no obvious effect on soil C/N ratio or wilting coefficient. The results of linear regression indicated that the improvement in soil water retention could be attributed to the increases in soil organic carbon and aggregate stability.

Effects of Biochar on Soil Microbial Biomass after Four Years of Consecutive Application in the North China Plain

The long term effect of biochar application on soil microbial biomass is not well understood. We measured soil microbial biomass carbon (MBC) and nitrogen (MBN) in a field experiment during a winter wheat growing season after four consecutive years of no (CK), 4.5 (B4.5) and 9.0 t biochar ha−1 yr−1 (B9.0) applied. For comparison, a treatment with wheat straw residue incorporation (SR) was also included. Results showed that biochar application increased soil MBC significantly compared to the CK treatment, and that the effect size increased with biochar application rate. The B9.0 treatment showed the same effect on MBC as the SR treatment. Treatments effects on soil MBN were less strong than for MBC. The microbial biomass C∶N ratio was significantly increased by biochar. Biochar might decrease the fraction of biomass N mineralized (K N), which would make the soil MBN for biochar treatments underestimated, and microbial biomass C∶N ratios overestimated. Seasonal fluctuation in MBC was less for biochar amended soils than for CK and SR treatments, suggesting that biochar induced a less extreme environment for microorganisms throughout the season. There was a significant positive correlation between MBC and soil water content (SWC), but there was no significant correlation between MBC and soil temperature. Biochar amendments may therefore reduce temporal variability in environmental conditions for microbial growth in this system thereby reducing temporal fluctuations in C and N dynamics.

Chromium, Cadmium, Nickel, and Lead in a Tropical Soil after 3 Years of Consecutive Applications of Composted Tannery Sludge

Agricultural use of tannery sludge (TS) may increase risks to soils. Thus, composting is recognized as one of the most suitable alternatives for TS recycling. Field experiments were carried out to evaluate the effects of composted tannery sludge (CTS) on chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb) accumulation in soil after 3 years. Soil samples were collected 60 days after CTS application. After 3 years, The CTS increased Cr and Ni content, while Cd and Pb contents decreased. The third year, Cr contents showed linear increases as CTS rates were applied. The application of CTS, after 3 years, in the 2.5, 5, and 10 Mg ha−1 increased Cr significantly (140.7%, 159.7%, and 19%, respectively) and Ni (32%, 53%, and 43.8%, respectively) contents in the soil surface layer. This means that consecutive amendments of CTS increase Cr contents in the soil and plants.

Soil microbial biomass after two years of the consecutive application of composted tannery sludge - doi: 10.4025/actasciagron.v36i1.17160

Because the agricultural use of tannery sludge may cause increased risks to soils, composting is recognized as one of the most suitable alternative for tannery sludge recycling. Experiments were conducted under field conditions to evaluate the effects of composted tannery sludge (CTS) on the soil microbial biomass and trace elements after two years of consecutive applications. The following five treatments were used: 0 (without CTS application), 5, 10, 20 and 40 ton ha -1 of CTS (dry basis). Soil samples were collected at 60 days after the CTS application at 0-20 cm depth. The CTS application promoted changes in the soil microbial biomass C (SMB-C) and N (SMB-N). In the first year, significant increases in the SMB-C and SMB-N were observed with the application of 10 ton ha -1 . Furthermore, CTS application increased the Cr content in the soil after two years of application.

Effect of biochar on soil respiration in the maize growing season after 5 years of consecutive application

The effect of biochar on soil respiration (Rs) over one maize-growing season was studied after 5 years of consecutive application in an intensive cropland in the North China Plain. The experiment was carried out in randomly arranged plots with four treatments being evaluated. Three replications were conducted per treatment: a control plot without biochar addition (CK), biochar incorporated at 4.5 t ha–1 year–1 (BC4.5), biochar incorporated at 9.0 t ha–1 year–1 (BC9.0), and incorporated wheat straw (SR). The Rs was determined throughout the growing season of maize in 2012. Soil temperature and moisture were measured simultaneously at 5 cm depth. The results showed that the seasonal and diurnal variations of Rs in the four different treatments were approximately equal, and there was a positive correlation between Rs and soil temperature. The Rs values of treatments BC4.5 and BC9.0 were significantly lower than of SR but not CK. Significant correlations between Rs and soil temperature and soil moisture were observed. Soil temperature had a stronger effect on Rs than did soil moisture, and Rs was more sensitive to soil temperature in the biochar treatments than in the SR and CK treatments. The application of biochar and straw increased the soil active organic carbon content, but an obvious relationship between Rs and the soil active organic carbon content was not found.

Impact of Fallow Programs and Fumigants on Nutsedge (Cyperusspp.) Management in Plasticulture Tomato

With the loss of methyl bromide (MeBr) and high prices of alternatives, tomato growers are applying lower fumigant rates or adopting a reduced system. Without the broad-spectrum control provided by the complete fumigant system, a fallow weed program might be needed to avoid an increase in pest pressure with consecutive years of application of the reduced-fumigant system. Nutsedges are among the pests of interest due to their fast reproduction by underground structures and ability to spread and quickly infest a field. Field trials were conducted between February and December of 2011 in Balm, FL, to evaluate the impacts of fallow treatments, fumigants, and halosulfuron on nutsedge control. The trial design was a split–split plot with main, sub-, and subsubplots being fallow, fumigant, and herbicide treatment, respectively. Fallow treatments were spaced evenly throughout the fallow season and consisted of sequential combinations of cultivation (C) and/or glyphosate (G) applied at 2.24 kg ae ha−1; including: C, CC, G, GG, CG, GC, GCG, and NO (nontreated control). Fumigant treatments included a reduced-fumigant system of 1,3-dichloropropene plus chloropicrin 40:60 (1,3-D + pic) at 281 kg ha−1, a complete fumigant system of dimethyl disulfide plus chloropicrin 79:21 (DMDS + pic) at 545 kg ha−1, and no fumigant (NoFum). Herbicide treatments were either two POST applications of halosulfuron at 39 g ai ha−1(Hal) or no halosulfuron (NoHal). In general, the fallow weed treatment GCG was the most effective in reducing nutsedge shoot emergence through the plastic mulch. When the reduced-fumigant system 1,3-D + pic was combined with GCG fallow treatment and halosulfuron (GCG:1,3-D + pic:Hal), no differences were found between this combination and the complete fumigant system DMDS + pic with halosulfuron and combined with CC, G, GG, CG, GC or GCG. This study shows the importance of adding a fallow weed program and halosulfuron to either a reduced or complete fumigation system to minimize the reproduction and growth of nutsedges.

Continuous and Residual Effects of Broiler Litter Application to Cotton on Soil Properties

The residual effect of broiler litter on soil properties is not well documented. Field studies were conducted in Coffeeville on an Ariel silt loam soil and Cruger on a Dubbs silt loam soil to evaluate the residual effect of repeated broiler litter application to cotton (Gossypium hirsutum L.) on soil properties. Broiler litter was applied at 0, 2.2, 4.5, and 6.7 Mg ha−1 and 4.5 Mg ha−1 plus 67 kg N ha−1 from 2002 to 2007. Phosphorus and K were applied as recommended by the Mississippi Soil Testing Laboratory. After 3 years of consecutive applications, in 2005 each plot was divided into two equal sub-plots where one half continued to receive the same treatments, whereas the other one half was not fertilized from 2005 to 2007. Soil samples were taken from all plots at the end of the experiment in 2007. Continuous broiler litter application over 6 years increased soil total C, N, microbial biomass C, and soil test P levels at both locations. However, soil bulk density was reduced at the highest broiler litter application rates only at Coffeeville. Three years after broiler litter application was terminated, at rates greater than 2.2 Mg ha−1 soil pH, total soil C and N, microbial biomass C, and soil test P levels were still greater than the control at Coffeeville location. In this study, we have shown that after 3 years broiler litter application to cotton resulted in positive residual effects on the soil nutrient pool and maintained soil fertility levels, particularly under no-till system.

Consecutive applications of brassica green manures and seed meal enhances suppression of Meloidogyne javanica and increases yield of Vitis vinifera cv Semillon

This study examined the result of 1–3 year application sequences of two brassica green manures (Indian mustard cv Nemfix and BQ mulch™), Nemfix seed meal and Nemacur ® on the suppression of root knot nematode Meloidogyne javanica in soil and roots, and the consequent improvement on vigour and productivity of Vitis vinifera cv Semillon. Soil examination revealed ca. 37–78% suppression of M. javanica populations when soil was amended with brassica green manures, Nemfix seed meal and Nemacur ® for 1–3 consecutive years compared to unamended soil. In all cases, M. javanica populations were significantly reduced after 1 year of treatment with a further reduction in the second year of treatment. The third year application did not have any significant reduction over the second year treatment. A suppression of M. javanica populations in soil after 3 consecutive years of application of brassica green manures, Nemfix seed meal and Nemacur ® significantly increased yield by 69–101% compared to the inoculated control (unamended) treatment. Three consecutive years of application of green manures and Nemfix seed meal significantly increased starch concentration in the roots to between 23 and 25% compared to the inoculated control treatment (concentration 14%). Fresh pruning weights were significantly increased by 35% in 2–3 consecutive years of application of Nemfix green manure treatment only compared to the inoculated control treatment. Applications of the green manures, Nemfix seed meal and Nemacur ® for 1–3 consecutive years did not have any significant effect on berry juice characteristics.

Influence of long‐term land application of Class B biosolids on soil bacterial diversity

To evaluate the effect of long-term annual land applications of Class B biosolids on soil bacterial diversity at University of Arizona Marana Agricultural Field Center, Tucson, Arizona. Following the final of 20 consecutive years of application of Class B biosolids in March 2005, followed by cotton growth from April to November 2005 surface soil samples (0-30 cm) were collected from control (unamended) and biosolid-amended plots. Total bacterial community DNA was extracted, amplified using 16S rRNA primers, cloned, and sequenced. All 16S rRNA sequences were identified by 16S rRNA sequence analysis and comparison to known sequences in GenBank (NCBI BlastN and Ribosomal Database Project II, RDP). Results showed that the number of known genera (identifiable > 96%) increased in the high rate biosolid plots compared to control plots. Biosolids-amended soils had a broad phylogenetic diversity comprising more than four major phyla: Proteobacteria (32%), Acidobacteria (21%), Actinobacteria (16%), Firmicutes (7%), and Bacteroidetes (6%) which were typical to bacterial diversity found in the unamended arid southwestern soils. Bacterial diversity was either enhanced or was not negatively impacted following 20 years of land application of Class B biosolids. This study illustrates that long-term land application of biosolids to arid southwestern desert soils has no deleterious effect on soil microbial diversity.

Mineral concentrations in herbage and soil in a Pinus radiata silvopastoral system in north‐west Spain after sewage sludge and lime application

SummarySilvopastoral systems in north‐west Spain can reduce the risk of fires and promote multi‐purpose forest land use. Fertilizer application is important for optimal pasture and tree production. The application rate of sewage sludge as a fertilizer is regulated and is based on its nutrient concentration, especially nitrogen. The aim of this study was to assess the effect of three consecutive years of application of different application rates of sewage sludge and inorganic fertilizer, with or without lime (2·5 t CaCO3 ha−1) on the ammonium, nitrate and exchangeable K, Ca and Mg contents in soil, and on the crude protein (CP), K, Ca and Mg concentrations in herbage in a silvopastoral system established under a 5‐year‐old Pinus radiata D. Don plantation with a density of 1667 trees ha−1. The experiment was started in autumn 1997, when a pasture mixture was sown (25 kg ha−1Lolium perenne, 10 kg ha−1Dactylis glomerata and 4 kg ha−1Trifolium repens). Changes in ammonium and nitrate content in the soil in response to liming and sewage sludge application reflected the initial pH of the soil. In general, liming increased the available Ca and Mg content in soil, and CP and Ca concentrations in herbage, but reduced exchangeable K content in the soil in the first year. Application of sewage sludge increased all of the measured nutrients in both soil and herbage.

A technique to produce aluminum color bands for avian research

We developed a technique to produce metal (aluminum) color bands, in response to concerns about leg injuries caused by celluloid-plastic color bands applied to Willow Flycatchers (Empidonax traillii). The technique involves color-anodized aluminum bands (unnumbered blanks and federal numbered bands), with auto pin-striping tape and flexible epoxy sealant, to create a variety of solid, half- and triple-split colors. This allows for hundreds of unique, high-contrast color combinations. During six consecutive years of application, these colored metal bands have resisted color fade compared to conventional celluloid-plastic bands, and have reduced leg injuries in the flycatcher. Although not necessarily warranted for all color-banding studies, these metal bands may provide a lower-impact option for studies of species known to be impacted by plastic color bands.

Resistance to azoxystrobin in Alternaria isolates from pistachio in California

Failure to control Alternaria late blight in a few California pistachio orchards was observed after only 3–4 years of consecutive applications of azoxystrobin-based fungicide programs. A total of 72 isolates of Alternaria alternata, Alternaria tenuissima, and Alternaria arborescens, the causal organisms of Alternaria late blight, were collected from pistachio orchards with (58 isolates) and without (14 isolates) a prior history of azoxystrobin applications. The sensitivity to azoxystrobin was determined in conidial germination assays. Isolates from orchards with a history of azoxystrobin applications had EC 50 values greater than 100 μg/ml, whereas isolates from orchards without a prior history of azoxystrobin usage had EC 50 values ranging from 0.008 to 0.045 μg/ml. Azoxystrobin resistance correlated with a single mutation in the cytochrome b (cyt b) gene causing a change of glycine to alanine at amino acid position 143. A pair of PCR primers AF and AR was developed that amplified a 226-bp DNA fragment of the cyt b gene containing the mutation site from all three Alternaria species but not from 30 other fungal species frequently found on pistachio. PCR-restriction fragment length polymorphism (PCR-RFLP) analysis using the restriction enzyme Fnu4HI allowed differentiation of the PCR fragment of wild type cyt b gene from that of mutated gene. This method will aid in a fast detection of azoxystrobin resistance in these three Alternaria species.

Global gridded emission inventories of α‐hexachlorocyclohexane

Emission factors of α‐hexachlorocyclohexane, the major isomer of technical hexachlorocyclohexane (HCH) for spray events and tilling events, are distributed on a 1°×1° longitude and latitude grid system. Estimations of global gridded α‐HCH emissions in 1980 and 1990 due to 15 consecutive years of application of technical HCH are presented. The total global usage of α‐HCH was estimated to be around 290 kt in 1980 and 59 kt in 1990. Total global α‐HCH emissions in 1980 were 184 kt, 92.5% of which was contributed by the current use of α‐HCH in 1980 and 7.5%, by the residues due to the use of technical HCH since 1966. Total global α‐HCH emissions in 1990 were 44 kt, 93% of which was contributed by the current use of α‐HCH in 1990 and 7%, by the residues due to the use of technical HCH since 1976. In 1980 approximately 74% of the global α‐HCH emissions originated in the Northern Hemisphere midlatitudes, followed by around 19% in the Northern Hemisphere tropics, while in 1990 approximately 54% of the global α‐HCH emissions originated in the Northern Hemisphere tropics, followed by around 37% in the Northern Hemisphere midlatitudes. Emissions of α‐HCH were strongly localized in Asia. Among total global α‐HCH emissions, 85% and 75% originated in Asia in 1980 and 1990, respectively. Study of trends of α‐HCH residue shows that α‐HCH can remain in the soil for more than 10 years after its ban in countries such as China and Japan. The trends of α‐HCH concentration in the soils in the Kitakyushu District, Japan, and Taihu Lake basin, China, estimated from our model fit the monitoring data in the same areas quite well. Qualitative uncertainty estimates have also been assigned on a regional basis.

Lack of Cross-Resistance of Imazaquin-Resistant Xanthium strumarium Acetolactate Synthase to Flumetsulam and Chlorimuron.

Acetolactate synthase (ALS) was isolated from a field population of cocklebur (Xanthium strumarium) that developed resistance to the herbicide Scepter following three consecutive years of application. The active ingredient of Scepter, imazaquin, gave an inhibitor concentration required to produce 50% inhibition of the enzyme activity that was more than 300 times greater for the resistant enzyme than for the wild-type cocklebur ALS. Tests with flumetsulam and chlorimuron show that the resistant ALS was not cross-resistant to these two other classes of ALS inhibitors.

Competição de adubos fosfatados no algodoeiro, em ensaio de longa duração

Após quatro anos de aplicações sucessivas de misturas de adubos contendo P ou P mais S, em ensaio permanente com o algodoeiro, fez-se rotação com cultivo de mucuna-preta na entressafra do quarto para o quinto ano, seguida de calagem visando à adequada correção da acidez do solo. No qüinqüênio 1978-1983, cultivou-se a variedade IAC 18 de algodoeiro, mantendo-se a mesma adubação da primeira fase, que, através de combinações de produtos comerciais, como sulfato de amônio, Nitrocálcio, superfosfato triplo, superfosfato simples e cloreto de potássio, forneceu anualmente às plantas N e K em doses constantes e P e S em doses variáveis. Sintomas de deficiência de enxofre, representados especialmente pelo "verde-limão" das folhas de ponteiro, tornaram-se evidentes a partir do quinto ano agrícola (primeiro da segunda fase), coincidindo com tendência para aumento de produtividade do algodoeiro. Entretanto, só após a correção da acidez do solo (pH em H2O ao redor de 6,2), é que a produtividade das plantas se estabilizou em nível alto, e as diferenças a favor das misturas contendo superfosfato simples tornaram-se estatisticamente significativas. Na segunda fase, as doses de 50 e 100 kg/ha de P2O5 proporcionaram acréscimos no volume de produção, respectivamente de 37 e 40%, quando se usou superfosfato triplo na adubação, e de 55 a 67% no caso do superfosfato simples. Em termos de lucro, o superfosfato simples proporcionou acréscimos sobre o triplo da ordem de 55 a 82%, em função da dose de P2O5 usada. Peso de capulho e comprimento de fibra também foram significativamente beneficiados pelo superfosfato simples, enquanto o fornecimento suplementar de enxofre, 120 kg/ha de S, não alterou as características gerais do algodoeiro adubado com a dose básica de 60 kg/ha de S. E proposto que se reavalie a necessidade de incorporar enxofre nas formulações comerciais de adubos, diante dos resultados obtidos.