Spatial analysis of cotton (Gossypium hirsutum L.) canopy responses to irrigation in a moderately humid area

Accurate irrigation scheduling is important to ensure maximum yield and optimal water use in irrigated cotton. This study hypothesizes that cotton water stress in relatively humid areas can be detected from crop stress indices derived from canopy reflectance or temperature. Field experiments were conducted in the 2003 and 2004 crop seasons with three irrigation treatments and multiple cultivars to study cotton response to water stress. The experiment plots were monitored for soil water potential (SWP), canopy reflectance and canopy temperature. Four crop stress indices namely normalized difference vegetative index (NDVI), green NDVI (GNDVI), stress time (ST) index and crop water stress index (CWSI) were evaluated for their ability to indicate water stress. These indices were analyzed with classic mixed regression models and spatial regression models for split-plot design. Rainfall was plentiful in both seasons, providing conditions representative of irrigated agriculture in relatively wet regions. Under such wet weather conditions, excessive irrigation decreased lint yield, indicating the necessity for accurate irrigation scheduling. The four crop stress indices showed significant responses to irrigation treatments and strong correlation to SWP at shallow (0.2 m) depth. Spatial regression models were able to accurately explain the effect of irrigation treatment, while classic split-plot ANOVA models were confounded by collinearity in data across space and time. The results also verified that extreme humidity can mask canopy temperature differences with respect to ambient temperature, adding errors to canopy temperature-based stress indicators.

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Urea hydrolysis in wetland soil amended with Sesbania aculeata green manure and rice straw

Summary The effect of incorporating sesbania and rice straw and of period of decomposition on urea hydrolysis was studied in a wetland soil under laboratory conditions. Urea hydrolysis proceeded more rapidly in the crop residue-amended soil than in the control soil, and increased with increases in the rate of addition of crop residues and with longer periods of decomposition. Irrespective of amendment treatment, urea hydrolysis followed first-order reaction kinetics, and rate constants in the unamended soil ranged from 0.021 to 0.024 h^-1 after urea application of 200 g N g^-1 soil. In the amended soil, hydrolysis rates ranged from 0.033 to 0.149 h^-1 with sesbania and 0.071 and 0.250 h^-1 with rice straw, depending on the length of decomposition period.     

Field appraisal of herbicide potential of sunflower leaf extract against Rumex dentatus

Comparative evaluation of sunflower aqueous extracts and commercially available synthetic herbicides was carried out in field trials. Crude aqueous extract was tested in 80 and 100% concentrations in plots where wheat was grown with Rumex dentatus in a 1:1 mix. In comparison with the synthetic herbicides (Buctril-Super^® and Chwastox^®) the aqueous extract failed to kill 100% of selected weeds, but the highest tested extract concentration completely overcame weed crop competition by reducing the weed biomass and increasing wheat yield significantly. The trial confirmed the herbicidal potential of sunflower allelochemicals against broad leaf weeds.     

Effect of Application Method on the Efficiency of Potassium Chloride in Wetland Rice on a Beidellitic Potassium Problem Soil

A greenhouse pot experiment evaluated the effect of incorporation and placement on the efficiency of KC1 in wetland rice on a K-problem soil with beidellitic clay mineralogy and high tendency to fix added K.
Placement turned out to be superior to incorporation by increasing significantly both grain and straw yields.

Zusammenfassung

Einfluß der Anwendungsmethode auf die Effizienz von Kaliumchlorid in Wasserreis auf einem beidellitischen Kali-Problem-Boden
In einem Gewächshaus-Gefäßexperiment wurde der Einfluß des Einmischens und der Plazierung auf die Effizienz von KC1 bei Naßreis in einem K-Problemboden mit beidel-litischem Ton, der eine starke Tendenz zur Fixierung von gedüngtem Kalium aufwies, untersucht. Die Plazierung erwies sich gegenüber einer Einmischung überlegen; dies galt signifikant sowohl für Korn- als auch Stroherträge.     

Comparative Ammonium and Potassium Fixation by some Wetland Rice Soil Clays as Affected by Mineralogical Composition and Treatment Sequence

Comparative fixation of NH₄ and K by wetland rice soils in relation to clay mineral composition and treatment sequence is of agronomic interest, but information on the subject is scanty. An attempt has been made to clarify this relationship by employing the normally recommended doses of fertilizers, 3 application sequences, and 5 soil clays of divergent mineralogies. The results show that montmorillonitic clay is the greatest fixer of NH₄, but least of K. X-ray amorphous clay also prefers NH₄ over K. Vermiculitic and beidellitic clays strongly fix both NH₄ and K. Soil clay consisting of hydrous mica, chlorite, and halloysite fixes low proportions of applied NH₄ and K. The sequence in which NH₄ and K are applied does not appear to affect the relative amounts that are fixed.     

Elimination of erythromycin in milk after intramammary administration in cows with specific mastitis: relation to dose,milking frequency and udder health

Elimination of erythromycin in milk following intramammary therapy of specific mastitis in cows was studied. Five cows received therapy in one quarter (G1), and eight in two quarters with five milked twice (G2) and three thrice a day (G3). Dose infused was 300 mg/quarter 12 h × 5 times. The drug concentrations in milk were determined using microbial assay technique with Micrococcus luteus as the test organism. Considerable variations occurred in the excretion of drug; levels for treated quarters being 8.25 to 37.61 μg/ml at first milking that declined rapidly at 24 h and no drug activity was observed beyond 36 h post treatment. In total, about 6–25% of the last infused dose appeared in the milk. Drug crossed to 1/15 quarter (G1), 6/10 quarters (G2) and all the six untreated quarters (G3). Crossover levels were significantly higher in mastitic quarters and for G3 cows, but duration of excretion remained same in all cases. It seems that crossover of erythromycin to untreated quarters is related to the udder health and dose infused.     

Major constraints on shisham (Dalbergia sissoo) plantations and pathological debate on dieback disease in Punjab,Pakistan

Today,shisham plantations in Punjab,Pakistan face major constraints,especially dieback disease.This article reviews the multidisciplinary team work by forest and plant pathologists and economists to resolve the confusions in the pathology of dieback disease.It is intended to be of practical use to the foresters and plant pathologists reporting on this issue.     

Properties of thermoplastic composites with cotton and guayule biomass residues as fiber fillers

This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical properties (ash, lignin and cellulose contents). A laboratory experiment was designed with five fiber filler treatments, namely control (oak wood fiber as the filler - OWF), cotton burr and sticks (CBS), CBS with 2% (by weight) second cut linters (CBL), CBS with 30% (by weight) guayule whole plant (CGP), and CBS with 30% (by weight) guayule bagasse (CGB). The composite samples were manufactured with 50% of fiber filler, 40% of virgin high-density polyethylene (HDPE), and 10% other additives by weight. The samples were extruded to approximately 32 × 7 mm cross-sectional profiles, and tested for physico-mechanical properties. The CBS and CBL had considerably lower bulk density than the other fibers. Cotton linters had the highest α-cellulose (66.6%), and lowest hemicellulose (15.8%) and lignin (10.5%) of all fibers tested. Guayule whole plant had the lowest α-cellulose and highest ash content. Both CBS and guayule bagasse contained α-cellulose comparable to OWF, but slightly lower hemicellulose. Evaluation of composite samples made from the five fiber treatments indicated that fibers from cotton gin byproducts and guayule byproducts reduced the specific gravity of the composites significantly. However, the CBS and CBL samples exhibited high water absorption and thickness swelling, but the addition of guayule bagasse reduced both properties to similar levels as the wood fiber. The CGP exhibited significantly lower coefficient of thermal expansion. Composite samples with the five different fiber fillers showed similar hardness and nail holding capacity, yet oak fibers imparted superior strength and modulus under flexure and compression with the exception of the compressive modulus of CGB composites. In general, both cotton ginning and guayule processing byproducts hold great potential as fiber fillers in thermoplastic composites.