Effects of Mechanical Sowing and Transplanting on Characteristics of Dry Matter Production in Middle-season Hybrid Rice

To clarify the effects of mechanical sowing and transplanting on dry mat- ter production of middle-season hybrid rice, a two-factor split plot design was used to study the effects of different sowing and transplanting methods and their interac- tion with the seedling number per hill or seeding time on dry matter accumulation, distribution and transformation of F You 498, a middle-season hybrid rice variety, under field conditions in 2012 and 2013. The results showed that there was a marked effect of the sowing and transplanting methods and their interaction with the seedling number per hill or seeding time on dry matter accumulation, distribution and transformation. The total population dry matter accumulation of the treatments with mechanical direct seeding （MDS） and machine-based transplanting （MT） was lower than that of the treatment with traditional manual transplanting （TMT）. How- ever, MDS had higher dry matter accumulation and accumulating rate in the joint- ing-earing stage,and maintained higher stem-sheath exportation, export rate and transformation than MT and TMT; MT had higher dry matter accumulation and ac- cumulating rate in the heading-maturity period than MDS and TMT. Moreover, the treatments with low seedling number per hill or early seeding enhanced the assimi- lation of dry matter after heading,the ratio of dry matter accumulation after earing to biomass yield and the contribution rate of dry matter accumulation after earing, and a reasonable early sowing was favorable to increase the harvest index of middle- season hybrid rice under mechanical sowing and transplanting conditions.

Analysis on Dry Matter Production Characteristics of Super Hybrid Rice

Six middle-season indica hybrid rice combinations, including five super hybrid rice combinations with the high yield about 10.5 t/ha and a check hybrid rice combination Shanyou 63 with a yield potential about 9.5 t/ha, were used as materials to study the dry matter production characteristics. The super hybrid rice showed a high ability in dry matter production and accumulation and its yield enhanced with the increase of dry matter accumulation. The advantage period of dry matter production in the super hybrid rice was mainly at the middle and late growth stages compared with the check. The grain yield had no significant correlation with the dry matter accumulation before the elongation stage while had a significantly positive correlation with the dry matter accumulation from the elongation to maturity stages in super hybrid rice. There were more dry matter in vegetative organs at the heading stage in the super hybrid rice but its contribution to yield （apparent conversion percentage） was averagely 4.3 percent points lower than that in the check. For crop growth rate （CGR）, the comparative advantage of super hybrid rice was at the middle and late stages, especially after flowering. Moreover, as the rising of leaf area index （LAI） and leaf area duration （LAD）, CGR enhanced. The total LAD and the mean of lAD per day of super hybrid rice was about 14.79% and 10.31% higher than those of the check, respectively. The results indicate that the high yield of super hybrid rice mostly comes from the products of photosynthesis after heading, which is shown by the increased CGR at middle and later stages. It is suggested that LAD character might be used to better explain the advantage in the dry matter production of super hybrid rice than LAI.

Nitrogen Uptake Dynamics and Dry Matter Production of Rice in Response to Nitrogen Fertilizer Application

Nitrogen is one of the most important nutrients in rice production but its uptake dynamics remained relatively unexplored. The present investigation evaluated uptake dynamics over the growing season at different levels of nitrogen fertilizer application. The experiment was conducted during Boro season （November-April） at Bangladesh Rice Research Institute experimental farm, Gazipur, Bangladesh. The experiment involved two modem rice varieties-BRRl dhan28 and BRRI dhan29 and six N rates： 0, 50, 100, 150, 200 and 250 kg·ha^-1. The N uptake pattern was determined at every 15 days from transplanting to maturity. At 150 kg·N·ha^-1, initially N uptake was 0.1 kg.hal.day1 which increased to 0.2 in BRRI dhan28 and 0.4 in BRRI dhan29, respectively. During 30 to 45 DAT, per day N uptake was 2.0 kg-ha1 in BRRI dhan28 and 2.2 in BRRI dhan29 which increased to the peak at 2.4 and 2.8 kg·ha^-1·day^-1 in BRRI dhan28 and BRRI dhan29, respectively, during 45 to 60 DAT. The grain yield showed a stronger correlation with N uptake during 45 to 60 DAT in both the varieties. The highest N uptake contributed to the highest dry matter production in both the varieties.

Establishment of ANEDr model for evaluating absorbed-nitrogen effects on wheat dry matter production

Applying mathematic models to evaluate absorbed-N effects on dry matter production at different developmental stages would help determine proper nitrogen management according to crop demands and yield target. Two field trials were carried out for establishing absorbed-N effects on dry matter production（ANEDr） model, using uniform design in 2010–2011and 2012–2013 winter wheat growing seasons in Hebei Province, China. Another field trial was carried out in 2010–2011for model validation. Dry matter and N concentration in leaf and non-leaf organs were measured at setting, jointing, anthesis, and maturity. Theory of best linear unbiased prediction（BLUP） was applied to analyse the N effects of leaf and non-leaf organs on dry matter production. Within ANEDr model, four N-affected phases at each stage were concerned,leaf absorbed-N effect before this stage, non-leaf organ absorbed-N effect before this stage,leaf absorbed-N effect at this stage, and non-leaf organ absorbed-N effect at this stage. In addition, developmental processes, genotype characters and temperature were three factors that determine each N effect. It was demonstrated that ANEDr model can precisely quantify absorbed-N effects on dry matter production with high correlation coefficient（r=0.95）. Comparing with other models, ANEDr model considered both leaf and non-leaf organs according to developmental processes of winter wheat, showed higher flexibility and simplicity, thus could be applied to different environments, cultivars and crops after parameter adjustment.

The heterotic effects on dry matter production and grain yield formation in hybrid rice

We studied the characteristics of dry matterproduction and matter partitioning in hybridrice and the relationships of them with heterot-ic effect in 1993. Two popular indica hybrids, Shanyou 63(Zhenshan 97A/Minhui 63 ) and Teyou 63(Longtepu A/Minhui 63), as well as theircommon restorer line, Minhui 63 (elite cultivar

Effects of clipping on dry matter production and nutrients in the fernland of Hong Kong

The dry matter production and its nutrient amounts varied significantly with time and period from April to June was a favourable season for plant growth. Dry matter production declined significantly with clipping. Especially, repeated cutting of high frequencies for the long term had a severe effect on dry matter production. However, N, P, and K amounts in dry matter production did not significantly decline because the concentrations of N, P, and K in the plants increased with clipping. Repeated cutting for long term is a reason why net primary production has been depressed in the most of upland areas of southern China.

Growth characteristics and grain yield of machine-transplanted medium indica hybrid rice with high daily yield

High-yield rice varieties with a suitable growth duration are required for mechanical transplanting in multiple cropping systems. Daily yield is an appropriate criterion for the selection of machine-transplanted rice varieties. The aim of this study was to investigate the growth characteristics and grain production in machine-transplanted medium indica hybrid rice with a high daily yield. We conducted a field experiment on 20 medium indica hybrid rice varieties in 2017 and 2018.Grain yield decreased significantly with growth duration between jointing and heading, but it increased with dry matter accumulation, growth rate between jointing and heading, dry matter partitioning to the stem plus sheath at heading, daily yield, and number of spikelets per panicle. Compared with the medium and low daily yield variety types, the high daily yield variety type increased shoot biomass by improving crop growth rate and dry matter accumulation amount between jointing and heading and after heading. The high daily yield variety type decreased the growth duration pre-heading and the proportions of dry matter partitioned to the leaf lamina at heading and maturity, but it also increased the post-heading accumulated dry matter in the grain and the remobilization of dry matter stored in the vegetative organs. Furthermore,the high daily yield variety type significantly increased the occurrence rate of tillers, which is beneficial for the formation of a larger panicle size and an increase in the grain-filling rate. These changes contributed to a 6.51–23.16% relative increase in grain yield of the high daily yield variety type. In conclusion, the selection of high daily yield indica hybrid rice varieties with shorter pre-heading growth duration, greater tiller occurrence rate and spikelet numbers per panicle, higher post-jointing growth rates and stem plus sheath dry matter accumulation at heading is suitable for machine-transplanted rice.

Use of Mussel Shells as a Soil Amendment:Effects on Bulk and Rhizosphere Soil and Pasture Production

Large quantities of mussel shells （66000-94000 t year^-1）, an alkaline material that can be used as a soil amendment, are generated as waste in Galicia, NW Spain. A field trial was carried out by planting different pasture species in a Haplic Umbrisol using a randomized block design with four blocks and six treatments （not amended control or soil amended with lime, finely ground shell, coarsely ground shell, finely ground calcined shell or coarsely ground calcined shell） to compare the effects of lime and mussel shells additions on a soil with a low cation exchange capacity and high AI saturation. The trial was established in March 2007, and samples of plants and soil were collected when plots were harvested in summer 2008 （separating the bulk and rhizosphere soil）. The soils were analyzed for pH, total C, total N, available P, exchangeable cations, effective cation exchange capacity and available micronutrients. Dry matter yield was measured in all plots and plants were analyzed for nutrients. Application of mussel shells and the commercial lime resulted in an increase in pH and exchangeable Ca and a decrease in exchangeable Al and Al were most noticeable in the rhizosphere. The amendment of Ca in the plant. saturation. The stability of pH over time was high. These effects also had a positive effect on dry matter yield and concentration

Physiological Responses of Zea mays Seedlings to Interactions Between Cadmium and Salinity

The effects of 0, 2.5, 5.0, and 10.0 pmol/L Cd^2＋（Cd（NO3）2.4H2O） and 0, 10, 25, 50, and 100 mmol/L NaCl on growth, photosynthesis and the content of some ions in maize （Zea mays L.） were investigated in the present study. With Increasing concentrations of Cd^2＋ or NaCI alone in Hoagland nutrient solution, the chlorophylls and starch content decreased. Combination treatment with salinity and cadmium increased the negative effects observed following the two stresses alone. Plants exhibiting growth retardation in response to one mild stress factor （25-50 mmol/L NaCl） became more tolerant to the other stress factor （Cd）. The exposure of plants to cadmium caused a partial reversal of the effects of salinity. Root and shoot growth, ion accumulation and levels of photosynthetic pigments were improved at moderate concentrations of the two stress factors Imposed jointly.