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991.
分蘖期土壤水分对早稻矿质养分吸收的影响 总被引:1,自引:0,他引:1
在池栽条件下研究了不同水分处理对早稻吸收氮磷钾及分蘖生产效率的影响。结果表明:土壤水分对早稻吸收N、P、K矿质元素有明显影响。随着土壤水分含量的提高,植株对矿质元素的吸收量显著提高。在分蘖初期,65%水分处理的植株对N、P、K的吸收量分别只有100%的74.1%,43.9%和50.8%,而在分蘖后期,则分别只有100%的41.4%,18.6%和27.5%。早稻矿质元素的分蘖生产效率以在85%土壤含水量时最高,其N、P、K的平均分蘖生产效率分别比100%高35.7%,140%和81.8%。平均分蘖生产效率表现为P〉K〉N。 相似文献
992.
吕志仁 《广西农业生物科学》1992,(2)
通过奇选42、广二矮104等7个水稻品种,分别配制不同的杂交组合,研究了水稻主要经济性状的遗传力,F_1与两亲本的相关,杂种各世代之间的相关,F代的主要经济性状之间的相关,F_4代构成产量的经济性状与单株谷粒产量的复相关和多元回归分析。结果表明,水稻的株高、千粒重、结实率、单株谷粒重和穗粒数的遗传力较高,这些经济性状在 F_1与两亲本的相关中,在杂种各世代之间的相关中,都表现出中度或高度的显著或极显著的正相关。每株穗数和每穗实粒数与单株谷粒产量,每株穗数和每穗粒数与单株谷粒产量,每株穗数和结实率与单株谷粒产量,在复相关和多元回归中,都表现为显著或极显著的水平。 相似文献
993.
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996.
On-farm varietal diversity is now highest in marginal agricultural environments because, unlike the case in more favourable
areas, modern varieties have not been a sufficiently attractive option for farmers to replace their landraces. However, the
continued survival of landraces on farm is dependent on the continuing failure of plant breeding to provide better alternatives.
Highly client-oriented breeding can produce suitable modern varieties for areas that were dominated by landraces. We examine
here the case of the adoption of two upland rice varieties in three states in eastern India, Jharkhand, West Bengal and Orissa,
where our surveys had confirmed low adoption of modern varieties in the upland ecosystem. The two new upland varieties were
readily accepted by farmers who rapidly adopted them on large proportions of their land. On-farm diversity is maintained by
the need to trade-off among varieties but once a variety with overall superiority was found this incentive was removed. The
new varieties from the client-oriented breeding did not have weaknesses that farmers had to trade-off against their landraces
so they were more likely to replace them. They also replaced older modern varieties. Farmers had previously maintained them
along with landraces because they had to trade-off the higher yield of Kalinga III against the more stable yield of landraces
or the higher yield of Vandana against the higher gain quality of the landraces. Only mean count per household could be used
to test the significance of the differences between individual years. In all states, this revealed a significant reduction
in landrace diversity with the adopting farmers when the addition of the two new varieties was not considered. Trends across
years for mean varietal count, total count and Shannon–Wiener index showed a significant decline in Orissa, irrespective of
whether the two new varieties were included in the analysis or not. In Jharkhand there was a significant decline only for
mean count when the new varieties were not included. In Orissa, it was possible to test if rare landraces were as readily
replaced as more common ones. Landrace replacement was unmitigated by increasing rarity yet the most rare landraces have the
highest priority for genetic conservation. Some landraces were completely replaced by the farmers in the sample despite a
diverse variety portfolio being a risk-reducing strategy in a region where there is a high risk of crop failure. There was
little environmental heterogeneity in the marginal, drought-prone areas to slow this decline. The new varieties had an impact
on the farming system because sometimes farmers brought additional upland into cultivation. They also introduced these varieties
into more favourable, medium land. The strategy of releasing two new upland varieties met with some success in maintaining
diversity. 相似文献
997.
M. Vikram Reddy V. P. Kiran Kumar V. Ravinder Reddy P. Balashouri D. F. Yule A. L. Cogle L. S. Jangawad 《Biology and Fertility of Soils》1995,19(4):317-321
Earthworms recorded during 1989–1993 across 15 soil management treatments, comprising three different tillagexthree organic amendments (bare, farmyard manure, and rice straw) and six perennial ley treatments, belonged to two endogeic species, Octochaetona phillotti (Michaelsen) and Lampito mauritii Kinberg, while in a nearby undisturbed natural revegetation area three species were found, including the above two and Octonochaeta rosea (Stephenson). The earthworm biomass showed significant temporal and spatial variations and was higher during the post monsoon period than in the early rainy season. No worm biomass was recorded during the dry season. In the tillage and organic amendment treatments, the biomass was drastically reduced from September 1989 to September 1991 after the application of carbofuran and some herbicides, and was significantly reduced during these two years compared to that of 1992. The maximum monthly earthworm biomass ranged between 2.5 and 17.9 g m-2 across the treatments and increased several-fold in the nearby natural revegetation area (75.9 g m-2). It significantly increased in perennial ley treatments compared to annual treatments with organic amendments. Thus the earthworm biomass varied significantly (P<0.01) across the 15 treatments, indicating discernible effects of soil management.Visiting Scientist (under the Rockefeller Foundation Environmental Research Fellowship in International Agriculture) 相似文献
998.
R. Maggs A. Wahid S. R. A. Shamsi M. R. Ashmore 《Water, air, and soil pollution》1995,85(3):1311-1316
Open-top chambers ventilated with ambient or chiarcoal-filtered air were used to assess the impact of air pollution on the yield of local cultivars of wheat and rice, at a site on the outskirts of Lahore. At this location, 6-h mean O3 concentrations reach 60 ppb in certain months, and annual mean NO2 concentrations are 20–25 ppb. The experiments showed significant yield reduction in two successive seasons which ranged from 33% to 46% in wheat and from 37% to 51% in rice. The major yield parameter affected was the number of ears or panicles per plant, although there was also evidence of small effects on 1000 grain weight and on the number of grains per ear/panicle. These results have significance in terms of the maintenance of agricultural yields as pollution emissions rise in south and south-east Asia. 相似文献
999.
1000.
水稻强化栽培下不同氮肥管理对产量与氮素利用的影响 总被引:2,自引:0,他引:2
以籼型单季超级杂交稻中浙优1号为材料,研究水稻强化栽培氮肥管理对产量与氮素利用率的影响。结果表明:水稻强化栽培与常规栽培对照比较,增产达11.1%-15.2%,氮肥回收率比对照高5.3%~26.9%,农学利用率比对照高67.2%~92.2%,生理利用率比对照高6.0%~80.5%。因此,在水稻生产上应用水稻强化栽培可以提高氮肥的利用,降低氮肥在环境中积累及对环境造成污染。此外,本文对水稻强化栽培下氮肥管理的高产机理进行了探讨。 相似文献