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PubMed2006

[Effects of tillage-cropping systems on methane and nitrous oxide emissions from permanently flooded rice fields in a central Sichuan hilly area of Southwest China].

Using the static opaque chamber method, a field experiment was conducted in situ for two years to study the effects of three cultivation systems on CH4 and N2O emissions from permanently flooded rice fields in a hilly area in Southwest China. The results show that the average CH4 fluxes from a permanently flooded rice field with a single middle rice crop and flooded with no winter crop (PF) were (21.44 +/- 1.77) mg x (m2 x h)(-1) and (3.77 +/- 0.99) mg x (m2 x h)(-1) during rice-growing and non-rice growing periods, respectively, where both values were much lower than many previous reports from similar regions in Southwest China. The annual CH4 emission was mainly occurred in the rice growing period, being only 23.2% of the total annual CH4 flux emitted from the non-rice growing period, though the latter occupied two thirds of a year. The annual average flux of nitrous oxide was (0.051 +/- 0.008) mg x (m2 x h)(-1) and the N2O emission also intensive in the rice growing period. However, being only 8.1% of total annual N2O flux emitted from the non-rice growing period. After implementing the rice-wheat rotation (RW) and rice oil-seed rape rotation (RR), the CH4 emissions were reduced substantially, only 43.8% and 40.6% of those of PF, respectively. However, the N2O emissions were increased after conducting RW and RR systems, which were 3.7 and 4.5 times larger than those of PF. The global warming potentials (GWPs) of the CH4 and N2O emissions under the three tillage-cropping systems were assessed in an integrated way. The results show that the integrated GWPs of the CH4 and N2O emissions are in the following sequence: PF>>RR approximately equal to RR. Within 20, 100 and 500 years spans, the GWPs of the CH4 and N2O emissions of PF were 2.6, 2.1 and 1.7 times larger than those of RW (or RR), respectively. After introducing rice-wheat or rice oil-seed rape rotation systems into the permanently flooded rice fields, the integrated GWPs of the CH4 and N2O emissions were decreased largely.

Air Pollutants↗
PubMed2004

[Accumulation and translocation of lead in soil-crop system of green food production].

In this paper, the accumulation and translocation of lead in soil-crop ecosystems were studied through fertilization with chemical fertilizer, manure and bio-fertilizer. The results showed that the soil total Pb content was decreased with soil depth. It was 11.14 and 9.37 mg x kg(-1) in 0-15 and 15-30 cm after harvest, respectively. Rice root absorbed lead from soil, and transferred it to stem-leaf and grain. The Pb content in rice plant was root>stem and leaf>grain, which was increased with rice growth. The grains of 606-14 and Liao 294 contained 0. 008 and 0.007 mg x kg(-1) of Pb, respectively, which is under the standard of green food. Variance analysis indicated that the grain yield of different varieties had a significant variance, but no significant variance was found among different treatments. It could be summarized that manure or bio-fertilizer could be the substitute of chemical fertilizer in producing rice.

Absorption↗
PubMed2004

Evaluating legume species as alternative trap crops to chickpea for management of Helicoverpa spp. (Lepidoptera: Noctuidae) in central Queensland cotton cropping systems.

Mounting levels of insecticide resistance within Australian Helicoverpa spp. populations have resulted in the adoption of non-chemical IPM control practices such as trap cropping with chickpea, Cicer arietinum (L.). However, a new leaf blight disease affecting chickpea in Australia has the potential to limit its use as a trap crop. Therefore this paper evaluates the potential of a variety of winter-active legume crops for use as an alternative spring trap crop to chickpea as part of an effort to improve the area-wide management strategy for Helicoverpa spp. in central Queensland's cotton production region. The densities of Helicoverpa eggs and larvae were compared over three seasons on replicated plantings of chickpea, Cicer arietinum (L.), field pea Pisum sativum (L), vetch, Vicia sativa (L.) and faba bean, Vicia faba (L.). Of these treatments, field pea was found to harbour the highest densities of eggs. A partial life table study of the fate of eggs oviposited on field pea and chickpea suggested that large proportions of the eggs laid on field pea suffered mortality due to dislodgment from the plants after oviposition. Plantings of field pea as a replacement trap crop for chickpea under commercial conditions confirmed the high level of attractiveness of this crop to ovipositing moths. The use of field pea as a trap crop as part of an area-wide management programme for Helicoverpa spp. is discussed.

Agriculture↗
PubMed2005

Possibilities for improving nitrogen use from organic materials in agricultural cropping systems.

Nitrogen release from organic nutrient sources in soil is influenced by a range of factors such as soil temperature and moisture, and chemical composition of the organic material. Chemical composition can, to a certain degree, be controlled to increase the synchronization of nitrogen (N) release with plant N demand, whereas climatic factors cannot be controlled and so must be taken into account when planning management measures. In this paper, we discuss different ways to affect N release through manipulation of the chemical composition of fresh or pretreated plant materials and animal manures, timing of incorporation, and intentional distribution during application. We conclude by giving an overview of off-farm options that may need to be implemented to achieve improved use of N, especially in agricultural systems with surplus N.

Agriculture↗
PubMed2001

Increasing nitrogen use efficiency of corn in midwestern cropping systems.

Nitrogen (N) loss from agricultural systems raises concerns about the potential impact of farming practices on environmental quality. N is a critical input to agricultural production. However, there is little understanding of the interactions among crop water use, N application rates, and soil types. This study was designed to quantify these interactions in corn ( Zea mays L.) grown in production-size fields in central Iowa on the Clarion-Nicollet-Webster soil association. Seasonal water use varied by soil type and N application rate. Yield varied with N application rate, with the highest average yield obtained at 100 kg ha(-1). N use efficiency (NUE) decreased with increasing N application rates, having values around 50%. Water use efficiency (WUE) decreased as N fertilizer rates increased. Analysis of plant growth patterns showed that in the low organic matter soils (lower water-holding capacities), potential yield was not achieved because of water deficits during the grain-filling period. Using precipitation data coupled with daily water use throughout the season, lower organic matter soils showed these soils began to drain earlier in the spring and continued to drain more water throughout the season. The low NUE in these soils together with increased drainage lead to greater N loss from these soils. Improved management decisions have shown that it is possible to couple water use patterns with N application to increase both WUE and NUE.

Agriculture↗
PubMed1985

Cropping systems and household food security: evidence from three West African countries.

The following four articles describe several aspects of the complex yet basic processes of food production and consumption in African settings. Three elements in the picture stand out as subjects of current research and development action: traditional food crops, seasonality and women's activities. It is important that specialists enhance their understanding of those processes and the dynamic interrelations among particular elements, in the interests of improved nutrition and rural development.

Agriculture↗
PubMed2002

Cadmium and zinc interactions and their transfer in soil-crop system under actual field conditions.

The transfer of Cd and Zn from calcareous soils nearby a non-ferrous mining and smelting bases to the spring wheat (Triticum aestivum L.) and corn (Zea mays L.) tissues and the interactions between the two metals concerned were investigated under actual field conditions. Samples of soils and entire crops were randomly collected during harvest time in 1998 in the Baiyin region. The soil metal contents showed that the furrows had been polluted (mean values: 3.16 mg kg(-1) for Cd; 146.78 mg kg(-1) for Zn) and the significant spatial variation of the soil contamination existed here (ranges, Cd: 0.14-19.3 mg kg(-1); Zn: 43.5-565.0 mg kg(-1)). The translocation ratios of the two metals from soil to crop parts in the region studied were relatively lower and the order of the element transfer in different plant tissues was root > stem > grain. The transfer ratio of element Cd was lower than that of element Zn. Cd and Zn uptake by the crop structures could be best described by four models (P < 0.01): linear; exponential; quadratic; and cubic. Apart from a linear relationship between the element Cd in the corn grains and soils, models were generally non-lincar. An analysis of Cd-Zn interaction mechanism led to the conclusion that the effects of the two metals were synergistic to each other under field conditions, in which increasing Cd and Zn contents in soils could increase the accumulations of Zn or Cd in the two crops.

Cadmium↗
PubMed2001

Economy of fertilizer nitrogen through organic sources in rain-fed rice-legume cropping systems in West Bengal, India.

Field experiments were conducted at a farmers" plot adjacent to the Regional Research Station, red and laterite zone, Sub-center Sekhampur (Birbhum district) of West Bengal, India, situated 23 degrees 24' N latitude, 87 degrees 24' E longitude, to study the effect of different bio- and organic sources of nutrients instead of total fertilizer N in terms of crop productivity in the sequence and building up of soil fertility. During the wet seasons of 1997 and 1998, 12 combinations of bio- and organic sources (crop residues, well decomposed cow dung, dhanicha as green manure) were substituted for 25-50% of N fertilizer applied on transplanted rice (Cv. IR 36). Subsequently, during the winters of 1997-1998 and 1998-1999, leguminous pulse crops like lentil (Lens culinaris [L.] Medic.), gram ( Cicer arietinum L.) and lathyrus (Lathyrus sativus L.) were grown with and without inoculation of Rhizobium. Results revealed that the application of inorganic N in combination with organic sources exhibited a significant increase in rice yield (3.60-3.84 t ha(-1) ) compared to the yield from sole application of N (3.19-3.26 t ha(-1) ). The study showed that about 25% of total applied N was saved without significant yield reduction with simultaneous improvement of soil physical properties (pH, organic matter, available N, P, K, and CEC). Seed yield of pulses (lentil, gram, and lathyrus) were more pronounced in the treatment inoculated with Rhizobium, with a saving of 42.6-48.4 kg N ha(-1). Therefore, the results suggest that the combined application of inorganic and organic N sources in a 75:25 ratio is a superior N-management practice with regards to crop yields as well as improvement of soil fertility.

Agriculture↗
PubMed2001

Chemical composition, ensiling characteristics, and apparent digestibility of summer annual forages in a subtropical double-cropping system with annual ryegrass.

A 2-yr study was conducted to determine the chemical composition and digestibility of silages made from forage sorghum, pearl millet, and tropical corn managed to optimize forage quality. Silages were ensiled in upright concrete silos lined with plastic and fed to heifers to determine in vivo apparent digestibility. Samples were collected before and after ensiling to determine ensiling characteristics and forage quality. After ensiling, tropical corn had the greatest dry matter (DM), the lowest crude protein, and the greatest water-soluble concentrations. Tropical corn silage had a pH of 3.96. The pH of forage sorghum silage was 4.09, and pearl millet had a pH of 4.50. Pearl millet had the lowest concentration of preensiled water-soluble carbohydrate, which likely caused the high pH in the silage. There were no differences among the forages in DM loss during ensiling in yr 2. Heifers fed pearl millet silage consumed more DM, but digestible DM intake was not different among the three groups of heifers. The results of this experiment indicate that pearl millet would be less desirable as a crop intended solely for silage production. Both forage sorghum and tropical corn could be grown specifically for ensiling based on DM digestibility. The decision on which crop to use should be based on factors such as production costs, forage yields, and local growing conditions rather than silage quality.

Animal Feed↗
PubMed2006

Behavior and fate of chlorpyrifos introduced into soil-crop systems by irrigation.

The effect of chlorpyrifos added in irrigation water to a red soil from Central South China on the growth of wheat and oilseed rape seedlings, together with its uptake, was studied in a pot experiment. Addition of chlorpyrifos (1-10 microg g-1) in a single irrigation with distilled water resulted in absorption of chlorpyrifos by wheat (0.257-4.50 microg g-1) and also oilseed rape seedlings (0.249-2.02 microg g-1) during 20 d of plant growth. An initial concentration of chlorpyrifos in soil that is equivalent to or below 10 microg g-1 did not significantly influence the growth of wheat seedlings. Similarly, an initial concentration equivalent to or below 5 microg g-1 did not significantly influence the growth of oilseed rape seedlings. The degradation rate of chlorpyrifos was 1.4-4.2 times larger in oilseed rape rhizosphere soil than in unvegetated soil. The numbers of bacteria and fungi in oilseed rape rhizosphere soil were 3.18 times and 1.84 times larger, respectively, than those in unvegetated soil. This helps to explain the difference in degradation rates obtained.

Biodegradation, Environmental↗
PubMed2006

Effect of cultivar, year grown, and cropping system on the content of tocopherols and tocotrienols in grains of hulled and hulless barley.

In a three-year period (2000-2002) total tocols (tocopherols and tocotrienols), content of vitamin E and its isomers (alpha-, beta+gamma-, delta-tocopherols and tocotrienols) were assessed in grain of 13 barley genotypes. The highest content of tocols (60.3-67.6 mg kg(-1)) and content of vitamin E (Vitamin E equivalent-18.0-20.1 mg kg(-1)) were determined in the waxy varieties Wanubet, Wabet, and Washonubet. Standard varieties, i.e. of a malting type (Krona and Kompakt), had statistically significantly lower content of tocols (49.9 and 53.6 mg kg(-1)) and vitamin E (15.7-16.1 mg kg(-1)) compared to the waxy varieties. The hulless waxy variety Washonubet had statistically significantly higher total content of tocols (67.6 mg kg(-1)) and alpha- tocotrienols isomer (42.1 mg kg(-1)) versus all other genotypes in the set. Chemical treatment and fertilization statistically significantly increased the content of tocols (by 4.7 mg kg(-1)), vitamin E (by 1.9 mg kg(-1)), isomer alpha-tocopherol (by 0.9 mg kg(-1)) and isomer alpha- tocotrienols (by 3.3 mg kg(-1)). The average values of alpha-tocopherols and alpha-tocotrienols in the set were 6.7 mg kg(-1) and 29.7 mg kg(-1), respectively. Some of the reciprocal lines created by us from the malting and waxy varieties are suitable for food use for high contents of all tocopherols and alpha-tocotrienols.

Agriculture↗
PubMed2006

Changes in the soil environment from excessive application of fertilizers and manures to two contrasting intensive cropping systems on the North China Plain.

Effects of excessive fertilizer and manure applications on the soil environment were compared in greenhouse vegetable systems shifted from wheat-maize rotations 5-15years previously and in wheat-maize rotations. N, P and K surpluses to the greenhouses were 4328, 1337 and 1466kgha(-1)year(-1), respectively compared to 346, 65 and -163kgha(-1)year(-1) to wheat-maize fields. Subsequently, substantial mineral N and available P and K accumulated in the soil and leaching occurred down the soil profile in the greenhouses. Soil pH under vegetables was significantly lower than in the wheat-maize fields, while the EC was significantly higher in the vegetable soils. The mean Cd concentration in the vegetable soils was 2.8 times that in the wheat-maize rotations. Due to excessive fertilizer application in greenhouse vegetable production in northeast China, excessive salt and nitrate concentrations may accumulate and soil quality may deteriorate faster than in conventional wheat-maize rotations.

Agriculture↗
PubMed2006

Analysis of denitrification genes and comparison of nosZ, cnorB and 16S rDNA from culturable denitrifying bacteria in potato cropping systems.

Bacterial denitrification in agricultural soils is a major source of nitrous oxide, a potent greenhouse gas. This study examined the culturable bacterial population of denitrifiers in arable field soils in potato (Solanum tuberosum L.) production and denitrification genes (nir, nor and nos) and 16S rDNA in those isolates. Enrichments for culturable denitrifiers yielded 31 diverse isolates that were then analysed for denitrification genes. The nitrous oxide reductase (nosZ) gene was found in all isolates. The majority of isolates ( approximately 90%) contained the cnorB nitric oxide reductase gene, with the remainder containing the qnorB gene. Nitrite reductase genes (nirS and nirK) were amplifiable from most of the isolates, and were segregated between species similar to previously isolated denitrifiers. Isolated strains were preliminarily identified using fatty acid methyl ester analysis and further identified using 16S rDNA sequencing. The majority of isolates (21) were classified as Pseudomonas sp., with smaller groups of isolates being most similar to Bosea spp. (4), Achromobacter spp. (4) and two isolates closely related to Sinorhizobium/Ensifer spp. Phylogenetic trees were compared among nosZ, cnorB and 16S rDNA genes for a subset of Pseudomonas strains. The trees were mostly congruent, but some Pseudomonas sp. isolates grouped differently depending on the gene analysed, indicating potential horizontal gene transfer of denitrification genes. Although Bosea spp. are known denitrifiers, to the best of our knowledge this is the first report of isolation and sequencing of denitrification genes from this bacterial genus.

Bacteria↗