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Better understanding of how the loess soils respond to topography and land use under catchment‐scale vegetation restoration is needed to enable science‐based land management interventions for the policy‐driven “Grain‐for‐Green” eco‐restoration program in the Loess Plateau of China. The objective of this study was to characterize the relationships of four selected soil quality indicators to land use under vegetation restoration and topography for a small catchment (0·58 km2) in the Loess Plateau. The major land uses established in the catchment are cropland, fallow (i.e., natural revegetation), grassland, and jujube orchard. The four soil quality indicators were soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphorus (STP), and mean root zone soil water content during the wet season (MRZSWwet). SOC, STN, and MRZSWwet were significantly different (p < 0·05) for different land uses. Grassland showed the highest values for these three properties, whereas cropland had relatively low values for SOC and STN. Land use had no effect on STP, although the lowest value was observed in grassland. Spatial analysis showed that various relations between soil quality indicators and topography (slope and elevation) were observed. These relations were generally weak for most of them, and they varied with land uses. Further analyses indicated that land uses, slope, and elevation had significant effects on the relations between different soil quality indicators. The results here should provide useful information for the further development of “Grain‐for‐Green” program. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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In rice, totally one hundred and three genotypes were evaluated for resistance against blast disease in three hot spot locations of Guyana. The experiments were conducted in spring and autumn seasons of 2015, 2016 and 2017. The modified upland blast nursery (UBN) method was adopted for screening blast resistance. The Additive Main effects and Multiplicative Interaction (AMMI) analysis was applied to understand the interaction between genotype (G) and environment (E). The results of all seasons at three locations showed the consistent expression of high resistance by genotype FL 127 followed by FG12–08 and FG12–273. The AMMI analysis of variance (ANOVA) revealed that, resistance was dominated by the genotype main effect. The magnitude of genotypes by environment (G x E) sum of square (SS) was 3.64 times smaller than genotype SS, and 6.74 times larger than environment SS. The analysis has indicated that the differences of the genotypes across the environment were not substantial. All of the seven environment vectors appeared to be positively correlated. The screening at Onverwagt Back, autumn 2016 (E7) and Black Bush Polder, spring 2015 (E5) were observed to be the most representative environment. This was clearly revealed by smaller average - environment axis (AEA) angle. Likewise, E4 (Canje, autumn 2015) was observed closer to the “ideal test environment”, thus suggested as an ideal environment for blast resistant screening. Also, genotypes clustered near the origin have showed stable blast disease resistant status and contributed little to both G and G x E. These genotypes proposed as useful ones for breeding disease resistant varieties and hybrids in rice. 相似文献
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Intercropping millet with cowpea is a widespread practice throughout the semi‐arid regions of West Africa. Low soil phosphorus (P) is one of the main limiting factors for crop production in this region. The objective of this study was to determine optimum methods and rates of P application to a millet/cowpea intercrop on a sandy, dunal soil of western Niger. Triple super phosphate was applied by three different methods: broadcast, in millet hills, and in cowpea hills. Three rates (0, 22.5, and 45.0 kg P/ha) were applied by each method. Treatments were replicated four times in a randomized complete block design. Cowpea yields were not affected by P applications, but millet yields were maximum with 45.0 kg P/ha applied to the millet hills. The 45.0 kg P/ha broadcast and millet hill applications resulted in significantly higher leaf P levels for millet, but no significant differences were found in cowpea leaf P levels. The 45.0 kg P/ha treatment applied to millet hills also resulted in the maximum P uptake, greatest biomass production, and highest economic yield. However, P use efficiency was higher in the treatment with 22.5 kg P/ha applied to the millet hills. Phosphorus management systems must be developed which optimize yield and economic return, as well as nutrient and water use efficiencies. 相似文献
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Persaud Rajendra Persaud Mahendra Saravanakumar Duraisamy Homenauth Oudho 《植物病害和植物保护杂志》2020,127(2):183-196
Journal of Plant Diseases and Protection - Grain discolouration has been noticed in rice over the years in Guyana. The disease has been a serious problem in affecting quality and yield of rice. A... 相似文献
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Many bottomland tree species are tolerant of compacted soil and perform well in urban environments; however, the mechanism underlying this tolerance is unknown. Increased soil water content has been shown to alleviate some of the effects of soil compaction on plant growth, presumably because increasing soil water reduces soil strength. We hypothesized that tree species tolerant of very wet soils would have opportunities for root growth in compacted soil when high soil water contents reduced soil strength, whereas species intolerant of bottomland conditions would not. We tested this hypothesis on flowering dogwood (Cornus florida L.), a mesic species intolerant of inundation, and silver maple (Acer saccharinum L.), a bottomland species. Seedlings of both species were grown in pots for 21 and 30 days, respectively, in a growth chamber in native loam soil maintained at various combinations of soil strength and soil water tension. Downward root growth rate decreased in response to increasing soil strength in both species. At low soil strength (0.6 MPa), downward root growth rate of dogwood seedlings slowed when soil was either excessively wet or dry, whereas root growth rate of silver maple seedlings increased linearly with soil water content. In moderately compacted soil (1.5 g cm(-3) bulk density), silver maple seedlings had greater root growth rate, root length per plant, and ratio of root length to root dry weight in wet soil (0.006 MPa soil water tension) than in moist and dry soils (0.026 and 0.06 MPa, respectively), even though mean oxygen diffusion rate (ODR) was only 0.28 &mgr;g cm(-2) (SE = 0.05). No such effect was detected in highly compacted soil (1.7 g cm(-3) bulk density) in either species. Mean ODR showed a weak positive correlation with soil water tension (r = 0.40, P = 0.07), but was unrelated to soil strength. We conclude that silver maple roots can grow in moderately compacted soil when high soil water content decreases soil strength, whereas dogwood is unable to take advantage of this opportunity. 相似文献
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This study examines how institutional varieties at the subnational (state) level influence firm-level innovation in an emerging economy—India. Knowledge of how institutional varieties influence firm-level innovation is derived principally from country-level studies involving multiple developed countries. Research on emerging economies is sparse and tends to follow country-level approaches involving multiple countries. Research involving a single emerging economy where there are substantial institutional varieties between regions is thin. The institutional varieties of some emerging countries are so striking that they can be viewed as several countries within a country, for example, India, China. This study contributes to the innovation literature on the role of institutional varieties on firm-level innovation by focusing on a different level of analysis—a single, emerging economy with substantial institutional varieties across the different states of India. Innovation in emerging economies is a topic of increasing academic interest. A multilevel study involving regional- and firm-level factors is employed. Firm-level data are from the World Bank Enterprise Survey and regional-level data are from statistical agencies in India. The results confirm that institutional varieties have major impacts on firm-level innovation. The research, policy, and managerial implications are discussed. 相似文献
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Variability in millet stands in West Africa is clearly visible as early as three weeks after planting. The objectives of this study were to determine the influence of pH and chemical toxicities on millet germination and seedling growth and to compare varietal tolerance of toxic conditions. A nutrient solution study was carried out with a series of Hoagland‐based nutrient solutions. Germination percentage was calculated, and root and shoot lengths were measured for one week. Critical values were determined for toxic elements. The only treatment which reduced germination percentage significantly was copper (Cu) concentrations >0.05M. Solution pH values between 5 and 7 resulted in the best root growth, though shoot growth was unaffected by pH. The roots were more sensitive than the shoots to several [aluminum (Al), boron (B), zinc (Zn)] of the elemental toxicities studied. Soil Al and manganese (Mn) levels may be high enough to have toxic effects on millet roots. However, natural soil iron (Fe), Cu, and Zn levels were much lower than the critical levels determined in the nutrient solution study. The improved varieties were more tolerant of Fe and Zn toxicity than the LOCAL variety, but the LOCAL variety was more tolerant of high B concentrations. 相似文献
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