Weed control and crop tolerance to propane flaming as influenced by the time of day

Time of day has been observed to affect flaming efficacy. The basis for the differential plant response is not well understood; however, daily variation in leaf relative water content (RWC) is thought to contribute to the response. Leaf RWC is the ratio of the amount of water in the leaf tissue compared to when fully turgid. To determine the influence of leaf RWC in plant response to propane flaming, greenhouse experiments were conducted during April and repeated in September of 2009. Two crops [4-leaf maize (Zea mays) and second trifoliate soybean (Glycine max)] and two weed species [5-leaf velvetleaf (Abutilon theophrasti) and 6-leaf green foxtail (Setaria viridis)] were flamed with four propane doses of 0, 29, 43 and 87 kg ha⁻¹ at 0, 4, 8 and 12 h after sunrise-HAS. Leaf RWC was measured before treatment application. Flaming treatment was conducted utilizing a hand flamer with one VT 2-23 C vapor phase burner positioned 20 cm above soil surface and angled horizontally at 30°. The propane pressure was 120 kPa and the application speeds were 1.6, 3.2 and 4.8 km h⁻¹. The plant responses evaluated were plant injury and fresh weight at 7 days after treatment (DAT). All plant species were more susceptible to flaming during the afternoon when they had lower leaf RWC at 8 HAS; however, the response of these plants did not differ with the plants flamed at 12 HAS. Green foxtail flamed at 87 kg ha⁻¹ at 0, 8 and 12 HAS had injury of 62, 76 and 82%, respectively. The same response was observed in velvetleaf which had 80% injury when flamed with 87 kg ha⁻¹ at 0 HAS and 93% injury when flamed at 12 HAS with the same propane dose at 7 DAT. Similar trends occurred for maize and soybean suggesting that leaf RWC could be one of the factors affecting plant response to flaming. Practical implication is that flaming operation should be conducted in the afternoon in order to improve efficacy of weed control and reduce propane consumption rate.     

Chlorocholine chloride mediated resistance mechanism and protection against leaf spot disease of Stevia rebaudiana Bertoni

Investigations have been carried out to determine the influence of chlorocholine chloride on induction of the resistance mechanisms of Stevia rebaudiana against leaf spot disease, caused by Alternaria alternata. The paper also focuses an impact of chlorocholine chloride induced resistance on reduction of leaf spot disease. Chlorocholine chloride is attributed to its significant role in defence responses through augmentation of phenol and salicylic acid content as well as stimulation of phenylalanine ammonia lyase and peroxidase activity in S. rebaudiana following inoculation with A. alternata. Histochemical studies revealed that fungal invasion as well as infection process was appreciably reduced in chlorocholine chloride treated plants through peroxidase-H₂O₂ mediated strengthening of cell wall. The overall study highlights the significant role of chlorocholine chloride in induction of resistance in S. rebaudiana against A. alternata.     

Citric acid loaded nano clay polymer composite for solubilization of Indian rock phosphates: a step towards sustainable and phosphorus secure future

Non-renewable nature of rock phosphate (RP) reserves coupled with open ended nature of P cycle makes it imperative for maximum utilization of available P resources. In this context, use of Indian RPs from Purulia and Udaipur along with citric acid loaded nanoclay polymer composite (CA-NCPC) as P source to costly diammonium phosphate (DAP) was investigated through an incubation experiment followed by a greenhouse experiment with wheat-rice cropping sequence in a Luvisol (pH 5.14, available P 13.5 mg kg^?1). Soil available P, crop yield parameters and dynamics of soil P fractions were taken to judge the efficacy of CA-NCPC in solubilizing RPs. Application of CA-NCPC and DAP resulted in 82% and 69% increase in available P over control, respectively under incubation study. Direct effect of treatment receiving CA-NCPC + RP on yield and P uptake by wheat was comparable with DAP but residual impact of CA-NCPC + RP (16.7 g pot^?1) was better than DAP (13.8 g pot^?1) in rice. The changes in inorganic P fractions were also significant as inclusion of RP increased calcium-P from 16.1 to 61.5 mg kg^?1. Results indicated potentiality of RPs treated with CA-NCPC as an alternate P source which could prove promising amidst P scarcity.     

Variability among isolates of <Emphasis Type="Italic">Fusarium udum</Emphasis> and the effect on progression of wilt in pigeonpea

Soft rot of Chinese cabbage is a disease of great economic importance to the State of Pernambuco, Brazil. The present study aimed to evaluate the effect of two calcium sources in different concentrations (calcium nitrate [Ca(NO₃)₂] at 0, 0.15 and 0.3 g l^?1 and calcium chloride (CaCl₂) at 0, 1 and 5 g l^?1) that were applied through two methods (leaf spraying and soil drenching) on the control of soft rot. Further, it aimed to analyze calcium absorption by the plant and to determine calcium’s role in leaf and cell structure using microscopy. Ca(NO₃)₂ applied by both methods was effective in controlling soft rot caused by Pectobacterium carotovorum subsp. carotovorum, as it reduced the disease by up to 48.5 % when sprayed onto the leaves (0.15 g l^?1). A significant increase in the leaf calcium content was observed only in the plants that were sprayed with higher doses of Ca(NO₃)₂ and CaCl₂. In all of the calcium treatments, light microscopy analyses revealed an increased number of chloroplasts and improved structuring of the palisade parenchyma, while transmission electron microscopy analyses revealed an increased cell wall thickness that was especially evident for the 0.15 g l^?1 Ca(NO₃)₂ treatment applied by leaf spraying and soil drenching.     

Polymorphism of BMPR1B,BMP15 and GDF9 fecundity genes in prolific Garole sheep

Tropical Animal Health and Production - Mutation studies in different prolific sheep breeds have shown that the transforming growth factor beta super family ligands viz. the growth differentiation...     

Application timing and adjuvant type affected saflufenacil efficacy on selected broadleaf weeds

Saflufenacil is a new herbicide being developed for pre-plant burndown and pre-emergence broadleaf weed control in field crops, including maize, soybean, sorghum and wheat. Field experiments were conducted in 2007 and 2008 in northeast Nebraska, USA to describe dose-response curves of saflufenacil applied in mid (early post-emergence, EPOST) and late May (late post-emergence, LPOST) with several adjuvants for spring emerging broadleaf weed control. Dose-response curves based on log-logistic model were utilized to determine the ED₉₀ values (effective dose that provides 90% weed control efficacy) for Convolvulus arvensis, Lactuca serriola, Lamium amplexicaule, Capsella bursa-pastoris, Taraxacum officinale, Thlaspi arvense and Conyza canadensis. In general, weed control efficacy was influenced by application timing and type of adjuvant. EPOST application of saflufenacil resulted better efficacy of saflufenacil compared to LPOST. Addition of spray adjuvants improved efficacy of saflufenacil. For example, 90% control of T. arvense was obtained at EPOST application with 251, 161, 96 and 59 g a.i. ha⁻¹ for saflufenacil applied alone, or tank-mixed with NIS (nonionic surfactant), COC (crop oil concentrate), or MSO (methylated seed oil), respectively. In contrast, the ED₉₀ values with LPOST application were 333, 201, 127 and 79 g a.i. ha⁻¹ for saflufenacil applied alone, or with NIS, COC and MSO, respectively. MSO was the best adjuvant, which provided the most enhancement of saflufenacil. COC was the second best, or similar to MSO, on many weed species. NIS provided the least enhancement of saflufenacil. The ED₉₀ values determined for different broadleaf weed species are within the proposed label dose of saflufenacil.     

Tolerance of selected weed species to broadcast flaming at different growth stages

Organic producers rank weeds as the most important pests that limit their crop production. In order to optimize the use of propane flaming as a weed control tool, the objective of this study was to test tolerance of selected weed species to broadcast flaming performed at different growth stages. Six annual species, including one grass [barnyardgrass (Echinochloa crus-galli)] and five broadleaves [field bindweed (Convolvulus arvensis), kochia (Kochia scoparia), ivyleaf morning glory (Ipomoea hederacea), velvetleaf (Abutilon theophrasti) and Venice mallow (Hibiscus trionum)] were flamed at three growth stages with six doses of propane. The propane doses applied were 0, 12, 31, 50, 68 and 87 kg/ha. Flaming treatments were applied utilizing a custom built flamer mounted on a four-wheeler moving at a constant speed of 6.4 km/h. Species response to propane were described by log-logistic models based on visual injury ratings and dry matter (DM) for each weed species. Overall response to flaming varied among species, growth stage and propane dose. Broadleaf weeds were more susceptible to flaming than the grass regardless of the growth stage. A dose of 76 kg/ha of propane was needed to obtain 90% DM reduction for 7-leaf (L) barnyardgrass compared to much lower doses of 40, 49, 55, 56 and 51 kg/ha propane for 8-L bindweed, 6-L kochia, 10-L morning glory, 7-L velvetleaf and 5-L Venice mallow, respectively. Moreover, the tolerance of both grassy and broadleaf weed species to broadcast flaming increased with increase in plant size. A 90% DM reduction in velvetleaf was obtained with 42, 56 and 102 kg/ha of propane for 5-L, 7-L and 16-L stages, respectively. The tested broadleaf weed species were effectively controlled (90% DM reduction) with propane dose of 30–60 kg/ha when flamed at early growth stages (3-L to 14-L), while the same dose of propane provided only 80% DM reduction in barnyardgrass when flamed at vegetative stages (4-L to 7-L). It was not possible to obtain 90% DM reduction in barnyardgrass when flamed at flowering stage with the propane doses tested in this experiment.     

In situ water transmission characteristics of a tropical soil under rice-based cropping systems

In soils under rice-based cropping systems in Asia water movement and distribution in the root zone of rice and dryland crops are important for efficient water management. Saturated hydraulic conductivities in the wetland soil profile were evaluated from measurements of hydraulic gradients and percolation rates in the field. The subsoil layer (15–60 cm) restricted percolation rate to a greater degree than the puddled top soil.Unsaturated hydraulic conductivities and soil water diffusivities in the soil profile under dryland conditions were obtained from simultaneous measurements of soil water content using the neutron moderation technique and the soil matric potential by tensiometers over time and soil depth. Soil matric potential versus hydraulic conductivity and soil water content versus soil water diffusivity relations of various soil depths were established. At equivalent soil matric potentials, the hydraulic conductivity of surface soil was greater than that of the subsoil layers. Soil water diffusivity at different depths responded similarly. The study describes a simple in situ technique to measure percolation rates in wetland rice fields and evaluation of water transmission properties of field soil profiles.