[Distribution characteristics of soil nitrogen and its influence factors in different typical zonal soils.] / ä¸åŒå ¸åž‹åœ°å¸¦æ€§åœŸå£¤æ°®ç´ åˆ†å¸ƒç‰¹å¾åŠå ¶å½±å“å› ç´ .

On the basis of field soil sampling, this paper investigated the distribution characteristics of soil different nitrogen (N) forms and its influence factors in the different typical zonal soils. The results showed that the concentrations of soil extractable total N, extractable organic N and adsorbed amino acids extracted with 0.5 mol·L-1 K2SO4 significantly increased along the altitudinal gradient in the different vertical soils, and their mean concentrations were greater than that in the horizontal soils. The concentrations of soil different N forms widely varied with the soil type in the different horizontal soils. On average, the concentration of soil adsorbed amino acids was approximately 5-fold greater than that of the free amino acids, representing 21.1% of soil extractable organic N. It indicated that the soil adsorbed amino acids extracted with the strong salt solution could serve as an important form of soil organic N. Pearson correlation analysis showed that extractable total N, extractable organic N, ammonium and amino acids in vertical soils were positively correlated with soil organic matter and total N (r=0.57-0.93, P<0.05), but negatively correlated with soil pH and nitrate (r=-0.37--0.91, P<0.05). In the horizontal soils, soil extractable total N, nitrate, organic matter, total N, alkali-hydrolyzable N and cation ions (e.g. K+, Ca2+, Mg2+) were all positively correlated with soil pH (r=0.36-0.85, P<0.05), whereas negatively correlated with soil ammonium and amino acids (r=-0.39--0.81, P<0.05).

[Effects of straw incorporation on rice carbon sequestration characteristics and grain yield formation].

A field experiment was conducted to study the effects of straw incorporation on rice dry matter accumulation and transportation, rice carbon sequestration and grain yield formation. The experiment included four levels of straw incorporation: 0 (control), 4000, 6000 and 8000 kg · hm(-2). Hybrid rice cultivar Zhongzheyou 1 was used in this experiment. The results showed that the average rice dry matter accumulation amount of the three straw incorporation treatments was increased by 63.03 g · m(-2) compared with the control, and that of straw incorporation of 6000 kg · hm(-2) showed the most favorable result, which was 154.40 g · m(-2) higher than the control. Effects of straw incorporation on rice dry matter accumulation showed the best performance from the maximum tillering stage to the full heading stage, and the dry matter accumulation at this stage was 71.25 g · m(-2) higher than the control. Compared with the control, the average dry matter exportation rate and apparent transformation rate from rice stem and leaf in the straw incorporation treatments were increased by 4.2% and 3.7%, respectively. The highest dry matter exportation rate and apparent transformation rate from rice stem and leaf were observed in the straw incorporation treatment of 6000 kg · hm(-2), which were increased by 12.8% and 11.1% compared to the control, respectively. The average rice carbon sequestration from the straw incorporation treatments was increased by 55.38 g · m(-2) compared with the control, and straw incorporation of 6000 kg · hm(-2) performed best with an increase of 17.8% compared with the control. Straw incorporation played a positive role in regulating the carbon sequestration of stem and leaf at the early growth stage and carbon sequestration of spike at the late growth stage. The average grain yield from the straw incorporation treatments was increased by 794.59 kg · hm(-2) (9.5% higher) compared with the control. Rice grain yields from the straw incorporation treatments of 6000 and 4000 kg · hm(-2) were significantly higher than the control, while rice grain yield from the straw incorporation treatment of 8000 kg · hm(-2) did not show a significant increase compared to the control. The rice grain yield was closely related to the yield components, and the increase of effective panicles may be the main reason for the higher grain yields in the straw incorporation treatments. Effective panicles in the straw incorporation treatments was averagely 8.41 spikes · m(-2) more than the control.

[Selenium cycling and transformation in paddy field and selenium nutrition of rice: a review].

Due to the alternate variation of soil redox potential and the particularity of soil components in paddy field, the selenium (Se) cycling and transformation in paddy soil are obviously different from those in upland soil, and can affect the Se availability in soil and the Se absorption and accumulation by rice. To deeply understand the Se cycling and transformation in paddy soil and the Se absorption and accumulation by rice is of great importance in studying the transformation of soil inorganic Se to organic Se. This paper summarized the researches on the cycling mechanisms and form transformation of Se in paddy soil and the metabolic mechanisms and absorption characteristics of Se by rice, and discussed the present status and development trend of the studies on the Se transformation in soil-rice system and the Se translocation in rice plant, which could provide references for the study of soil Se availability and the cultivation of Se-enriched rice.

[Dynamic changes of rice (Oryza sativa L.) tiller angle under effects of photoperiod and effective accumulated temperature].

Using rice variety DI508 as test material, a field experiment of different seeding dates and a test with plant growth chamber were conducted to study the dynamic changes of rice tiller angle under effects of different photoperiod and effective accumulated temperature. Under field condition, the tiller angle of DI508 plants changed gradually into erect after 10-15 days of photoperiod becoming shorter (since the Summer Solstice on 21st June), irrespective of seeding dates (4th April, 5th May, and 4th June). Under controlled photoperiod, the tiller angle changed in the same way as in the field. Shorter lighting treatment (10 hours) advanced the tiller angle change, while longer lighting treatment (14 hours) delayed the change. Effective accumulated temperature had no effects on the tiller angle change of DI508.

[Effects of rice-duck farming system on biotic populations in paddy field].

A field experiment was conducted to study the effects of rice-duck farming on the related biotic populations in paddy field. The results showed that rice-duck farming had greater effects on the occurrence and damage of pests, pathogens and weeds, as well as the amount of pests' natural enemies in paddy field. The population of rice planthopper and leafhopper decreased by 64.8% and 78.5% after 12 and 42 days of duck-release, and the weeds decreased by 67.7% and 98.1% after 15 and 45 days of duck-release, respectively, compared with the control. The sheath blight index at the maximum tillering stage and full-heading stage in the rice-duck plots were 40.4% and 62.0% lower than those in the control plot, respectively. The population of spiders in duck-released field was increased obviously, which in turn decreased the damage of rice pests.

[QTL mapping and interaction analysis of genotype x environment (Fe2+ -concentrations ) for mesocotyl length in rice (Oryza sativa L.)].

A recombinant inbred lines (RILs) population derived from a cross between Zhenshan97B and Miyang46 was used for detecting QTLs with additive effects and additive-by-additive epistasis for rice mesocotyl length. A linkage map consisting of 207 DNA markers,distributing on the 12 chromosomes of rice,was employed for QTL mapping by using software QTL Mapper 1.6 of mixed linear model. Rice mesocotyl length under germination conditions with 4 different FeSO4 concentrations (0, 1.79, 7.16, 14.32 mmol/L) was measured 7 days after planting. A total of 6 QTLs with significant additive effects on chromosome 1, 5 and 9, with variance explained of 3.5%-11.4%, eleven QTLs with significant additive x additive epistatic effects on chromosome 1, 2, 3, 4, 5, 8 were detected, with variance explained of 4.5%-8.1%. In addition, one QTL for environmental interaction (Fe2+ -concentrations) was detected.