Agronomic effectiveness of cationic phosphate impurities present in superphosphate fertilizers as affected by soil pH

The general concept that low-water-soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)-P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)-potassium (K)-P compounds present in superphosphates [Fe 3 KH 8 (PO 4 ) 6·6H 2 O, H8, and Fe 3 KH 14 (PO 4 ) 8·4H 2 O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg -1 as neutral ammonium citrate (NAC)+H 2 O-soluble P. Reagent-grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg -1 included. Also, mixtures of both Fe-K-P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg -1 ) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water-soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low-water-soluble P source cannot be deemed as ineffective at high soil pH. Copyright © Taylor & Francis Group, LLC.

Estudo da degradação do herbicida propanil em campos de cultivo de arroz

Pós-graduação em Química - IQ

Estrutura genética de populações de Rhizoctonia oryzae-sativae do arroz em São Paulo, Brasil, e em meta, Colômbia, e potencial adaptativo do patógeno à Urochloa spp

Pós-graduação em Agronomia - FEIS

Susceptibility of adult and larval stages of the horn fly, Haematobia irritans, to the entomopathogenic fungus Metarhizium anisopliae under field conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Gas exchange rates, plant height, yield components, and productivity of upland rice as affected by plant regulators

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Rapid degradation of propanil in rice crop fields

Propanil and its major degradation product, 3,4-dichloroaniline (DCA), were monitored in surface water and soil samples from two rice fields of the Ebre Delta area (Tarragona, Spain) following agricultural application. On-line solid-phase extraction (SPE) (water) and Soxhlet extraction (soil) followed by liquid chromatography/diode array detection (LC/DAD) were used for the trace determination of both compounds. Unequivocal confirmation/identification was conducted by using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry, LC/APCI/MS (using negative and positive ionization modes). Concentrations of the herbicide propanil in water samples varied from 1.9 to 55.9 mu g/L. Propanil degraded very rapidly to DCA, and high concentrations of this product were found, varying from 16.5 to 470 mu g/L in water and 119 +/- 22 mu g/kg in soil samples. No detectable DCA (<0.001%) was found in the applied pesticide formulation, indicating that DCA formation took place after propanil application. These field results compared favorably with laboratory experiments showing that humic interactions had a strong influence on the pesticide degradation. The half-lifes under real conditions for propanil and DCA, calculated using a first-order decay, were 1.2 and 1.6 days, respectively.

Level crossing rate of Nakagami-m fading signal: Field trials and validation

Field trial measurements are used to validate the level crossing rate formula derived in an exact manner recently for the Nakagami-m signal. The formula reveals an excellent fit to measurements in situations other than those for which the Rice model is more appropriate.

Degradation of rice pesticides and their stability during storage of samples

Transformation of pesticides is directly related to the environmental conditions during application and transport of these compounds in the ecosystem. Rice fields include peculiar conditions, relatively high temperatures and wet conditions, leading to degradation processes, different from that observed in other agricultural systems. This article presents the degradation routes of some characteristic rice insecticides and herbicides under field conditions. A compilation of the pesticides that are usually applied during rice cultivation is included, with their main physico-chemical parameters. The stability of the pesticides by solid phase extraction systems during storage of rice samples is also discussed.

Root distribution, nutrient uptake, and yield of two upland rice cultivars under two water regimes

Upland rice (Oryza sativa L.) cultivation has been increasing in global importance due to the decreasing water availability for flood- irrigated rice. The use of sprinkler irrigation to supplement rainfall and the identification of cultivars more adapted to lower water availability could be effective alternatives for producing upland rice without yield losses while using less water. The objective of this field study was to evaluate the root distribution, plant nutrition, and grain yield of two drought tolerant upland rice cultivars under two water regimes in the Cerrado Region of Brazil during two growing seasons. The main plots were two water regimes (rainfed and sprinkler-irrigation plus rainfall). Subplots were two upland rice cultivars Carajás and IAC 201. Low water availability reduced root growth by 7% and grain yields were from 2644 to 4002 kg ha-1 on average for rainfed and sprinkler irrigation treatments, respectively. Carajás had a significantly better root distribution, nutrient uptake, and higher grain yield (3732 kg ha-1) compared with IAC 201 (2914 kg ha-1) averaged over two growing seasons and water regimes. There were no treatment interactions. Our results suggest that, even when cultivars with a higher tolerance to less water availability are used, using sprinkler irrigation to augment limited rainfall during dry periods may be a viable method to increase upland rice grain yields. © 2013 by the American Society of Agronomy.

The no-tillage system and cover crops-Alternatives to increase upland rice yields

Upland rice (Oryza sativa L.) cultivation has been increasing in importance in Asia while water availability for irrigation has been decreasing because of rapid growth in industry and urban centers. Therefore, the development of technologies that increase upland rice yields under aerobic conditions, thereby saving water, would be an effective strategy to avoid a decrease in global rice grain production. The use of the no-tillage system (NTS) and cover crops that maintain soil moisture would prove advantageous in the move toward sustainable agriculture. However, upland rice develops better in plowed soil, and it has been reported that this crop does not perform well under the NTS. Therefore, the aim of this study was to investigate the effect of cover crops on upland rice grain yield and yield components sowed in a NTS. A field experiment was conducted during two growing seasons (2008-2009 and 2009-2010), and treatments consisted of growing rice under five cover crops in a NTS and two control treatments under the conventional tillage system (plowing once and disking twice). Treatments were carried out in a randomized block design with three replications. Our findings are as follows: On average, Brachiaria brizantha (12.32Mgha-1), Brachiaria ruziziensis (11.08Mgha-1) and Panicum maximum (11.62Mgha-1) had outstanding biomass production; however, these grasses provided the worst upland rice yields (2.30, 2.04, and 2.67Mgha-1, respectively) and are not recommended as cover crops before upland rice. Millet and fallow exhibited the fastest straw degradation (half-lives of 52 and 54 days, respectively), and millet exhibited the fastest nitrogen release (N half-life of 28 days). The use of a NTS was promising when millet was used as a cover crop; this allowed the highest upland rice yield (3.94Mgha-1) and did not statistically differ from plowed fallow (3.52Mgha-1). © 2012 Elsevier B.V.

Population genetic evidence that basidiospores play an important role in the disease cycle of rice-infecting populations of Rhizoctonia solani AG-1 IA in Iran

The fungus Rhizoctonia solani AG-1 IA causes sheath blight, one of the most important rice diseases worldwide. The first objective of this study was to analyse the genetic structure of R. solani AG-1 IA populations from three locations in the Iranian Caspian Sea rice agroecosystem. Three population samples of R. solani AG-1 IA isolates were obtained in 2006 from infected rice fields separated by 126-263km. Each field was sampled twice during the season: at the early booting stage and 45days later at the early mature grain stage. The genetic structure of these three populations was analysed using nine microsatellite loci. While the population genetic structure from Tonekabon and Amol indicated high gene flow, they were both differentiated from Rasht. The high gene flow between Tonekabon and Amol was probably due mainly to human-mediated movement of infested seeds. The second objective was to determine the importance of recombination. All three populations exhibited a mixed reproductive mode, including both sexual and asexual reproduction. No inbreeding was detected, suggesting that the pathogen is random mating. The third objective was to determine if genetic structure within a field changes over the course of a growing season. A decrease in the proportion of admixed genotypes from the early to the late season was detected. There was also a significant (P=0·002) increase in the proportion of loci under Hardy-Weinberg equilibrium. These two lines of evidence support the hypothesis that basidiospores can be a source of secondary inoculum. © 2012 BSPP.

Alternative substrates in the production of lettuce seedlings and their productivity in the field

Based on the hypothesis that alternative substrates should improve the yield of lettuce crops by producing better quality seedlings, the objective of this work was to evaluate the effect of different substrates on the production of seedlings of this species, and their growth in the field. The study was in two stages. The first consisted of the production of lettuce seedlings, and the second assessed their development in the field. Four alternative substrates were tested, obtained by mixing together a sieved vermicompost from which all clumps had been removed, sterilized sand, charred rice husks and basalt powder. The commercial substrate, Plantmax HA®, was also tested. In the first phase, which was conducted in a completely randomised design with four replications, the height, root length, number of leaves, leaf area and dry weight of the seedlings were all evaluated 28 days after sowing. In the second phase, which was carried out in the field in a randomised block design with four replications, the plants were harvested 50 days after transplanting and the head diameter, fresh weight, number of leaves and leaf and stem dry weight were evaluated. The alternative substrates produced larger seedlings in less time than the commercial substrate, resulting in a reduction of 10 days in the total crop cycle. The reduction in the time between sowing and harvesting, together with those aspects relating to sustainability, are the main advantages of the use of alternative substrates, since in the field crop production did not differ between treatments.

Cover crops affecting levels of ammonium and nitrate in the soil and upland rice development

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Leaf gas exchange and yield of three upland rice cultivars

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)