Impact of Commercial Organic Ameliorants on Nitrogen and Phosphorus Concentrations of Maize Biomass at Ninth Leaf and Silking Growth Stages

The response of grain yield, biomass yield and harvest index of maize to the application of commercial organic ameliorants was inconsistent and poor. Hence it was hypothesized that the supply of N and P to maize plants was inadequate during vegetative growth, resulting in low concentrations of the two nutrients in maize biomass. The effects of nine ameliorants on the N and P concentrations of maize plants at ninth leaf (V9) and silking (R1) stages of maize were studied over three years at Bothaville (8% clay), Ottosdal (12% clay) and Potchefstroom (34% clay). All ameliorants were applied as prescribed by manufacturers. The N and P concentrations in maize biomass of the ameliorants at V9 and R1 were lower, comparable or higher, showing that the inconsistent and poor response of yield parameters can not be ascribed to inadequate uptake of N and P. A matter of concern that justifies thorough investigation, is the prescribed use of Crop care and Growmor with partial and of Montys and Promis with no NPK fertilization, an unsustainable practice over the long term. Characterization of the active ingredient(s) of the ameliorants is deemed also of importance for better insight.

The effects of straw‑returning and inorganic K fertilizer on the carbon–nitrogen balance and reproductive growth of cotton

Background:Many studies have indicated that straw-returning could meet part or even all of the potassium(K)demand for crop growth in the field,but few have compared the effects of crop straw as K source and inorganic K fertilizer on carbon–nitrogen(C–N)balance of cotton and the reproductive growth.To address this,field experiments were conducted using the cotton cultivar,Siza 3,under there treatments(CK as control group one,no crop straw and inorganic K fertilizer were applied;K150 as control group two,150 kg·ha^(-1) of K2O was applied;and W9000,9000 kg·ha^(-1) wheat straw,which could provide K2O about 150 kg·ha^(-1),was incorporated into soil).Results:Although the final reproductive organ biomass did not differ between W9000 and K150,W9000 had a higher ratio of reproductive organ biomass to total biomass(RRT),suggesting that straw-returning was more conducive to the allocation of biomass to reproductive organs.The theoretical maximum biomass of reproductive organ was higher,but the average and maximum accumulation rates of reproductive organ biomass were 2.8%∼8.3%and 2.5%∼8.2%lower under W9000 than K150.Also,the duration of rapid-accumulation period for reproductive organ biomass(T)was 2.0∼2.8 d longer under W9000 than K150,which was a reason for the higher RRT under W9000.Straw-returning altered the dynamics of leaf K with the growth period,so that W9000 had a more drastic effect on leaf C metabolism than K150.Consequently,lower soluble sugar/free amino acid and C/N ratios were measured under W9000 than K150 at boll-setting(BSS)and boll-opening(BOS)stages.Higher leaf net photosynthetic rate,sucrose phosphate synthase and sucrose synthase activities,and lower acid invertase activity were observed under W9000 than K150 at BSS and BOS and these were more conducive to sucrose accumulation.However,less sucrose was measured under W9000 than K150 at these stages.This should be because straw-returning promoted the assimilate transport capacity when compared with inorganic K fertilizer application,which also explained the higher RRT under W9000 than K150.The lower acid invertase activity under W9000 inhibited the conversion of sucrose to other sugars,hence lower contents of soluble sugar and starch were measured under W9000 than K150.Conclusion:Under low K condition,crop straw as K source can increase the assimilate transport from source to sink,leading to lower C/N ratio in leaf and higher allocation of biomass to reproductive organs than inorganic K fertilizer.

Study on Reproductive Growth Characteristics and Seed Germination of Eucalyptus dunnii in Sichuan Province

Studying the flowering development and seed germination of Eucalyptu dunnii and mastering the reproductive growth law can provide a theoretical basis for seed garden construction. In this study,a blooming plant growing in Zitong County was selected as the experiment subject. The results were as follows： florescence date of Eucalyptus dunnii was Mid-late February to mid to late October. Depending on morphologic change,flowering can be divided into 6 phases： Flower bud differentiation stage,inflorescence formation stage,opercle color change stage,capsule enlargement and shedding ring formation stage,flowering period,seed development stage. The development process of the buds on the same inflorescence was basically the same,the growth of buds near the base of the same branch was faster than that of the top buds,and the development of flower buds in different positions was random. There were 3-4 ovary cavities in a capsule. The number of shriveled seeds was far more than the number of effective seeds,and the average of each capsule contained five normal seeds which could develop into seedlings.

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment,photosynthesis in plants can be regulated systemically.Currently,the majority of studies are carried out with various plants during the vegetative growth period.As the reproductive sink improves photosynthesis,we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.Therefore,changes of light intensity within canopy,chlorophyll content,gas exchange,and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.In this study,a high planting density of maize drastically reduced the light intensities in the lower canopy,and increased the difference in vertical light distribution within the canopy.With the increase of vertical heterogeneity,chlorophyll content,light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf(EL) and the fourth leaf below the ear(FLBE) were decreased gradually,and the ranges of declines in these parameters were larger at FLBE than those at EL.Leaves in the lower canopy were shaded artificially to further test these results.Partial shading(PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.Removing the tassel and top leaves(RTL) not only improved the vertical light distribution within the canopy,but also reduced the differences in photosynthetic characteristics between the two leaves.Taken together,these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment;slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Effects of sand burial on dune plants: a review

Burial of different growth stages of plants （e.g., adult plants, seedlings and seeds） is frequent in dune ecosystems. The soil micro-environment, which differs from surface conditions, influences the survival and growth of dune plants. To sum up knowledge about the survival mechanisms of plants under sand burial and to promote practical rehabilitation of dune vegetation, we reviewed relevant published literature and concluded that： （1） Focus in recent years has been on impacts of sand burial on seed germination and seedling emergence. Generally, shallow burial increased seed germination and seedling emergence, but deeper burial was negative. Buried at the same depth, large seeds showed higher germination and seedling emergence rates, attributed to larger energy reserves. （2） Survival, growth and reproduction rates of dune plants show plasticity in response to sand burial. Long-term deep burial is fatal because it creates a physical barrier which overcomes the vertical growth of plants, reduces photosynthetic leaf area, and limits oxygen availability to roots. Modest burial, on the other hand, is advantageous for growth and reproduction of many dune plants, due to protection from excessive temperature and drought. （3） There are few reports concerning effects of sand burial on plant physiology, but a limited number of studies indicate that partial burial increases water use efficiency, chlorophyll content, transpiration rate and net photosynthetic rates. The antioxidant protective enzyme system and osmolyte balance were reported to be involved in the mechanisms of dune plant resistance to burial.