Effect of gypsum and calcium carbonate on plant yield and chemical composition and calcium availability in a non-saline sodic soil
SummaryThe availability of Ca from different levels of gypsum and calcium carbonate in a non-saline sodic soil has been investigated. Different levels of tagged gypsum (Ca45SO4.2H2O) and calcium carbonate (Ca45CO3) (i.e. 0, 25, 50, 75, and 100 per cent of gypsum requirement) were mixed thoroughly in 3.5 Kg of a non-saline alkali soil (ESP, 48.4; ECe, 2.68 millimhos/cm). Dhaincha (Sesbania aculeata) — a legume and barley (Hordeum vulgare L.) — a cereal were taken as test crops. Increasing levels of gypsum caused a gradual increase in the yield of dry matter, content of Ca and K in the plant tops and Ca:Na and (Ca+Mg):(Na+K) ratios in both the crops. Application of calcium carbonate caused a slight increase in the dry matter yield, content of Ca and Mg and Ca:Na and (Ca+Mg):(Na+K) ratios in barley, however, in case of dhaincha there was no such effect. Gypsum application caused a gradual decrease in the content of Na and P in both the crops. Total uptake of Ca, Mg, K, N and P per pot increased in response to gypsum application. The effect of calcium carbonate application on the total uptake of these elements was much smaller on dhaincha, but in barley there was some increasing trend.Increasing application of tagged gypsum and calcium carbonate caused a gradual increase in the concentration and per cent contribution of source Ca in both the crops, although, the rate of increase was considerably more in dhaincha. The availability of Ca from applied gypsum was considerably more than that from applied calcium carbonate. Efficiency of dhaincha to utilize Ca from applied sources was considerably more (i.e. about five times) than that of barley
Growth and Cationic Accumulation by Four Species of Plants as Influenced by Various Levels of Exchangeable Sodium1
SODIUM often makes up a considerable fraction of the total exchangeable cations in soils of arid regions; in many alkali soils Na is the predominant exchangeable cation present. The adverse effects of exchangeable Na upon the physical properties of soils are generally recognized and may be explained on the basis of the influence of this cation upon the swelling and dispersion of soil colloids. The causes of the poor growth of plants often observed upon soils containing a high proportion of exchangeable Na are not completely understood. McGeorge (14) and Breazeale and McGeorge (5) have shown that the high pH values of soils which are frequently associated with the presence of exchangeable Na may be responsible for various nutritional disorders in plants. There is also evidence that a high degree of saturation of the soil exchange complex with exchangeable Na may in itself be quite detrimental to plant growth. Ratner (17) studied the influence of various proportions of exchangeable Na and Ca upon the growth of oats_ and wheat in pot experiments and found that these crops failed to grow at exchangeable-Na-percentages of 60 to 70. He attributed plant failure to an insufficiency of Ca for plant nutrition and in a subsequent study (18) showed that wheat seedlings were unable to absorb Ca from soil having an exchangeable-Na-percentage of 40. In a similar study, Thorne (19) found that growth and Ca uptake by tomatoes were reduced when Na made up 40% of the exchangeable cations in the cultured media. Van Itallie (21), in a comprehensive pot study of growth and cationic uptake by Italian rye grass in relation to the proportions of various exchangeable cations supplied in soil, found that growth of this species was adversely affected at an exchangeable-Na-percentage of 26 and prevented at an exchangeable-Na-percentage of 51. Accumulation of Ca, Mg, and K by the top parts of this plant was found to decrease as the proportion of exchangeable Na supplied in the soil was increased. The influence of various levels of exchangeable Na upon growth and nutrient uptake by various plant species has also been studied in pot experiments by others including Lehr (13), Marshall (15), and Joffe and Zimmerman (12). Bower and Turk (3) have obtained evidence that natural soils containing high proportions of exchangeable Na may not furnish adequate supplies of Ca and possibly Mg to alfalfa. The purpose of the experiment reported herein was to obtain further information regarding the influence of various levels of exchangeable Na upon plant growth and cationic accumulation under controlled cultural conditions. In order to broaden the scope of the experiment four plant species thought to vary widely as regards their tolerance to exchangeable Na were studied. The species used were dwarf red kidney beans, garden beets, and Rhodes and Dallis grasses.
Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier
Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11MJ/Nm3 for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16gH2/kg biomass. For biomass oxygen/steam gasification, the content of H2 and CO reaches 63.27–72.56%, while the content of H2 and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H2/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.