An approach to soil testing with special reference to the zinc requirement of rice paddy soils

Abstract

Experiments were conducted to seek a better basis for soil testing of rice paddy soils. Soils were incubated under variable conditions of simulated flooding, and then extracted with DTPA⁵ . The amounts of Cu, Zn, Mn and Fe extracted were sensitive to the imposed soil conditions. Good correlations between Zn extracted from simulated flooded soils and Zn uptakes by rice from flooded soils in pots, suggest that this approach to soil testing may be more useful for paddy soils than existing tests on air dried soils.     

Mild drying of sandy soil can physically limit the uptake of phosphorus by rainfed lowland rice in northeast Thailand

ABSTRACT

Poor response of rice to phosphorus (P) fertilization and low phytoavailability of soil P have been reported in sandy rainfed fields in northeast Thailand. In order to evaluate the effects of mild soil drying on the uptake of P by rainfed lowland rice, we carried out nutrient omission trials for nitrogen (N) and P at Ubon Ratchathani Rice Research Center under rainfed and flooded conditions. The surface soil was classified as sandy loam. To avoid severe soil drying and drought stress in the rainfed field, soil water potential at a depth of 20 cm was maintained at the field capacity (> ?20 kPa) by flush irrigation. The effects of flooding and drying on the soil properties were also evaluated in the laboratory using soils with diverse textures in and around the center. In the field experiments, the above-ground biomass of rice plants (RD6) did not respond significantly to P fertilization in the rainfed field, although it responded positively to N fertilization. Root length in the surface 10 cm under the rainfed condition was significantly smaller than that under the flooded condition due partly to the increased soil hardness upon drying, but this could not quantitatively explain the large discrepancy of P uptake observed between the rainfed and flooded conditions. Under the rainfed condition, the P uptake did not increase significantly, even when the concentration of soil Bray P was tripled by transferring the surface soil from the flooded to the rainfed field. From the laboratory experiments, it was further suggested that soil P was supplied mainly by diffusion and that the effective diffusion coefficient for P can become less than one-tenth of the value in the flooded field when the sandy soil with clay at around 10% dried to ?100 kPa. Our results suggest that the uptake of P by the rainfed lowland rice grown in sandy soil can be limited physically by mild soil drying that reduces the supply of P to roots by diffusion rather than the chemical extractability of soil P.     

水稻专用配方肥增效剂的应用及其作用机理研究

以中稻培两优 93为材料 ,对配方肥增效剂的增产机理进行了研究。盆栽试验结果表明 ,配方肥增效剂能显著促进根系的生长 ,极显著提高根系体积、总吸收面积和活跃吸收面积 ,但对根系活力影响不大。增效剂对水稻植株下部叶片光合性能有一定影响 ,促进叶绿素含量增加、光合速率增大 ;还可提高处理水稻植株的气孔导度和蒸腾速率 ,改善养分在植物体内的运输条件 ,增加根系吸收养分的动力。配方肥增效剂能提高水稻植株的分蘖能力 ,增加干物质积累量。配方肥增效剂处理比配方肥处理增产约 8.6% ,减少化肥用量 10%和 20%。     

The uptake of phosphate by barley plants from soil under aseptic and non-sterile conditions

The uptake of phosphorus by barley plants growing in soil has been compared in the presence and absence of microorganisms. The soil chosen for study was basaltic loam which earlier investigations had shown required the addition of supplementary phosphate to obtain successful growth of plants.Despite a rapid turnover of the phosphorus in microorganisms as a result of death and lysis, less was absorbed by plants grown under non-sterile conditions causing a considerable reduction in the yield of dry matter. These microbial effects were obviated by the addition of a small quantity of KH₂PO₄ (0.15 m-equiv/500 g soil). In this soil therefore, competition appears to exist between microorganisms and plants similar to that demonstrated previously in water culture.     

Tubificid role in soil mineralization and recovery of algal nitrogen by lowland rice

Uptake of blue-green algal nitrogen (N) and total N uptake by lowland rice (Oryza sativa) was affected by tubificid (Oligochaeta) presence in submerged soils. Recovery of algal ¹⁵N by the first crop was 24–43% but only 4–7% for the second, and recovery was determined by both the method of algal application (surface vs buried) and the presence of tubificids. Tubificid activities reduced recovery of algal N by rice, increased its total N content and doubled losses of ¹⁵N to the atmosphere. Soil N uptake by rice was increased by tubificid presence. Soil N mineralization, measured as NH₄⁺ production, was doubled over 7 days by their activities and algal mineralization was also apparently enhanced. The NH₄⁺ release rate of Limnodrilus sp. was 4.11 ± 0.06 ng NH₄⁺-N mg ash free dry wt^?1 h^?1. Effects of tubificids on rice nutrition are discussed.     

Evolution of dinitrogen and nitrous oxide from the soil to the atmosphere through rice plants

Summary It is commonly assumed that a large fraction of fertilizer N applied to a rice (Oryza sativa L.) field is lost from the soil-water-plant system as a result of denitrification. Direct evidence to support this view, however, is limited. The few direct field, denitrification gas measurements that have been made indicate less N loss than that determined by ¹⁵N balance after the growing season. One explanation for this discrepancy is that the N₂ produced during denitrification in a flooded soil remains trapped in the soil system and does not evolve to the atmosphere until the soil dries or is otherwise disturbed. It seems likely, however, that N₂ produced in the soil uses the rice plants as a conduit to the atmosphere, as does methane. Methane evolution from a rice field has been demonstrated to occur almost exclusively through the rice plants themselves. A field study in Cuttack, India, and a greenhouse study in Fort Collins, Colorado, were conducted to determine the influence of rice plants on the transport of N₂ and N₂O from the soil to the atmosphere. In these studies, plots were fertilized with 75 or 99 atom % ¹⁵N-urea and ¹⁵N techniques were used to monitor the daily evolution of N₂ and N₂O. At weekly intervals the amount of N₂+N₂O trapped in the flooded soil and the total-N and fertilized-N content of the soil and plants were measured in the greenhouse plots. Direct measurement of N₂+N₂O emission from field and greenhouse plots indicated that the young rice plant facilitates the efflux of N₂ and N₂O from the soil to the atmosphere. Little N gas was trapped in the rice-planted soils while large quantities were trapped in the unplanted soils. N losses due to denitrification accounted for only up to 10% of the loss of added N in planted soils in the field or greenhouse. The major losses of fertilizer N from both the field and greenhouse soils appear to have been the result of NH₃ volatilization.     

The relationship between boron soil test results and boron uptake by bean plants

Abstract

Boron sensitive crops, kidney beans and soybeans, were grown in pots containing soil collected from a beet field and a nearby pasture. Two soil extraction procedures were used to measure boron concentrations in the soils. Dilute acid was used to extract what is believed to be readily available boron. A modified‐Soxhlet apparatus, which employed continuous leaching with hot water, measured what is believed to be slowly available boron. Plant boron status was determined by analyzing the above ground portion of the plants grown in two soils. The amount of boron in the plant tops provides an indication of biologically available boron or that boron actually available to plants. Although kidney beans and soybeans extracted more boron from the beet soil, both soil extraction procedures indicated that the concentration of boron was higher in the pasture soil. Neither extraction procedure proved reliable in predicting plant response.     

Studies on the nitrification in soil,with special reference to the population of nitrifier

A number of papers have been published on nitrification in soil. The problem of the nitrification has become increasingly important because of the appearance of new forms of nitrogenous fertilizers such as ammonium chloride or urea, etc.     

Solubilization of phosphate by rice plants growing in reduced soil: prediction of the amount solubilized and the resultant increase in uptake

Previous work has shown that rice plants growing in reduced soil are able to solubilize P by inducing an acidification in the rhizosphere through H⁺ produced in Fe²⁺ oxidation by root–released O₂, and by the direct release of H⁺ from the roots to balance excess intake of cations over anions. In this paper, equations for the diffusion and interaction of P and acid in soil are developed to predict the resultant increase in P uptake by the roots. Good agreement was obtained between the profiles of P and pH in the rhizosphere measured in the previous experiments, and those predicted using the equations with independently measured parameter values. The equations showed that solubilization accounted for over 80% of the P taken up. Measurements of the solubilization parameters in a range of reduced rice soils showed that H⁺ addition increased the quantity of P that could be desorbed per unit weight of soil and the concentration of P in solution, in all the soils tested. The quantity of P solubilized per unit H⁺ added at a given solution P concentration varied about 50–fold between soils, with a median of 11.9 mmol P per mol H⁺. The native soil solution P concentration varied 50–fold (median = 0.91 UM) and the soil pP buffer power (the quantity of P desorbed per unit decrease in –log of the P concentration in solution) varied 100–fold (median = 0.36 mmol kg^?1 pP^?1); the soil pH buffer power varied 7–fold (median = 0.075 mmol kg^?1 pH^?1). Calculations indicated that, in most of the soils tested, rice plants would depend upon solubilization for the bulk of their P.     

水稻对氮素的吸收、分配及其在组织中的挥发损失

应用¹⁵N示踪技术研究了水稻不同生育期吸收的¹⁵N在各器官中的分配,以及后期植物组织中的挥发损失。结果发现,水稻在分蘖期吸收的氮量少于在幼穗分化期吸收的氮量;在分蘖期吸收的¹⁵N,标记结束时氮素主要分配于水稻的叶片中,至成熟期¹⁵N有39%转运至水稻子粒中;水稻在幼穗分化期吸收的¹⁵N,标记结束时氮素主要分配在水稻茎和叶鞘中,至成熟期¹⁵N有46%转运至水稻的子粒中;水稻在分蘖期和幼穗分化期吸收的氮素在后期可以通过植株组织挥发损失,至成熟期损失的比例分别达16.7%和13.4%。     

Background level of indium and gallium in soil with special reference to the pollution of the soils from zinc and lead smelters

The mean and range of indium content in unpolluted soils (Humic Andosols, Eutric Fluvisols, and Mollic Gleysols) was found to be 0.037 (0.016–0.078) μg/g dry wt. In soils polluted by common heavy metals, elevated values of indium up to 1.92 μg/g dry wt were observed together with an increase of cadmium, zinc, and lead. In contrast to indium, gallium content in polluted soils was nearly the same as that in unpolluted soils throughout the profiles. The mean and range of gallium content in all unpolluted and polluted samples was 14.2 (12.8–16.3) μg/g dry wt. The indium and gallium contents in 4 Canadian reference soils were also analyzed.     

Copper and zinc uptake by celery plants grown on acidic soil amended with biosolids

For trace elements, such as copper (Cu) and zinc (Zn), the bioavailability of these elements, Cu and Zn, in biosolids is important because both are essential elements and both are potential contaminants when biosolids are land applied. A greenhouse study was conducted in factorial experiment based on a completely randomized design (CRD) with four replications on a soil treated with four rates of Cu (0, 50, 100, and 150 mg/kg) and four rates of Zn (0, 150, 300, and 450 mg/kg) on celery plants to investigate the distribution and mobility of these elements as well as growth and antioxidant changes of celery. The results of antioxidant changes were inconclusive due to irregular changes with Zn and Cu applications. However, generally the results show that Cu did not affect superoxide dismutase (SOD) or peroxidase (POD) activities in most of the treatments. On the other hand, Zn stimulated SOD and POD activities in most of the treatments. The photosynthesis rate decreased with the applications of Cu and Zn at the rates above 100 and 300 mg/kg and increased in low Cu concentration (50 mg/kg) compared to S (soil without biosolid).     

Studies on microbial population in the rhizosphere of higher plants with special reference to the method of study

Introduction

Many previous investigations, beginning with the observations of Hiltner¹⁹, have established the fact that soil in the rhizosphere contains a higher quantity of microorganisms than soil which is not within the influence of the plant root. It has been shown also that the balance between certain physiological groups^4,21,43,45, as well as that between morphological types of bacteria or fungi^30,50 is changed in the rhizosphere. In addition, Canadian investigators^23,34,62) have reported a change in the balance of certain nutritional groups of soil bacteria in the rhizosphere. Two excellent reviews^6,22) covering these papers have recently appeared. Since then a number of papers^{2,7,9,11,13,15-18,25,26,33,36,38-40,48,54,57-60,63)} concerning various aspects of the microbial population of the rhizosphere have been published.     

The significance of plant energy status for the uptake and incorporation of NH4-nitrogen by young rice plants

Uptake and assimilation of inorganic N in young rice plants has been studied with labelled N (N-15). Depletion of the plants' carbohydrate content, obtained by a preceding dark period, resulted in a drastic reduction of NH₄ ⁺-N uptake. Plants exposed to low light intensity showed diminishing NH₄ ⁺-N uptake rates as compared with plants exposed to full light intensity, the latter showing constant NH₄ ⁺-N uptake rates during the whole experimental period. The percentage of labelled insoluble N in total labelled N was not significantly affected by a preceding dark period, whereas the low light intensity resulted in a lower proportion of insoluble N in roots and shoots. The incorporation of labelled N into the insoluble fraction (proteins, nucleic acids) was higher in plants fed with NH₄ ⁺-N than in those fed with NO₃ ^-.

The uptake of NH₄ ⁺-N was not significantly affected by NO₃ ^-, whereas the NO₃- uptake rate was considerably reduced in the presence of NH^{4 +}-N. Low energy status of plants affected the nitrate uptake more than the uptake of NH₄ ⁺-N. The results show that uptake and assimilation of inorganic N depend much on the energetic status of plants. Nitrate uptake and assimilation is more sensitive to low energy conditions than NH₄ ⁺-N.     

Dissolution of slag fertilizers in a paddy soil and Si uptake by rice plant

Abstract

Maize (Zea mays L.) cv. Ganga 2 was grown in refined sand at three levels of copper: deficient (0.00065 mg L^-1), adequate (0.065 mg L^-1), and excess (6.5 mg L^-1), each at three levels, deficient (0.00065 mg L^-1), adequate (0.065 mg L^-1), and excess (6.5 mg L^-1) of zinc. Excess Cu magnified the zinc deficiency effects in maize by lowering further the biomass, the concentration of leaf Zn, activities of carbonic anhydrase, aldolase, and ribonuclease and intensified the visible foliar symptoms of Zn deficiency. The effects of Cu deficiency, low dry weight, the concentration of leaf Cu and activities of cytochrome oxidase and polyphenol oxidase were enhanced by excess Zn. Synergism was observed between combined deficiency of Cu and Zn and Cu or Zn deficiency, because the depression in the parameters characteristic of Cu or Zn deficiency was more pronounced when both Cu and Zn were deficient than when Cu or Zn was deficient. Antagonism was observed in some parameters between combined excess of Cu and Zn and Cu or Zn excess. Dry weight was decreased further when both Cu and Zn were in excess than when either Cu or Zn was in excess. After the infiltration of Cu and Zn together to the leaf discs from deficient Cu-deficient Zn treatment, the increase in the concentration of leaf Zn and the activities of aldolase, carbonic anhydrase, polyphenol oxidase, and cytochrome oxidase was more pronounced than after the infiltration of Cu or Zn singly. Discontinuance of excess Zn supply from the excess Zn-deficient Cu treatment increased the concentration of leaf Cu and activities of polyphenol oxidase and cytochrome oxidase and lowered the concentration of Zn. Similarly the discontinuance of excess Cu supply from the leaf discs in the “excess Cu-deficient Zn” treatment increased the leaf Zn concentration and the activities of carbonic anhydrase and aldolase.     

A radiotracer technique for studying the nutrient release from different fertilizer materials and its uptake by plants

Abstract

In the technique presented, ³⁵S was used to label the soil available sulfur pool in intact pasture cores, which were subsequently treated with different sulfur fertilizers. Dilution of the ³⁵S in the soil by sulfur released from the fertilizers was monitored by measuring the changes in specific radioactivity of sulfur in plants growing in the cores. The results showed the effects of fertilizer form, particle size and application rate on the supply of sulfur to plants. This technique will be useful for making direct comparisons of the ability of commercially available fertilizers to maintain the supply of sulfur to plants.     

Physicochemical properties of the soils associated with shifting cultivation in Northern Thailand with special reference to factors determining soil fertility

Abstract

Recently agricultural activity in the mountainous area of northern Thailand has increased and problems relating to soil fertility have arisen. In order to gain basic information about the soil properties associated with shifting cultivation, physicochemical properties of the surface soils (0–10 cm) and subsoils (30–40 cm) were investigated in selected villages in the area. The physicochemical properties of the soils studied are summarized as follows: 1) The soils were rich in organic matter, content of which ranged from 11.4 to 63.3 g C kg^?1 in the surface soil. 2) The pH(H₂O) of the soils mostly ranged from 5 to 7 and soil acidity was more pronounced in the deeper horizons. In the surface soils, exchangeable Ca and Mg were generally dominant, whereas exchangeable Al was often predominant in the subsoils. 3) Most of the soils showed a medium to fine texture with more than 30% clay. The clay mineral composition was characterized by various degrees of mixture of kaolin minerals and clay mica with, in some cases, a certain amount of 2:1-2:1:1 intergrades. 4) According to the ion adsorption curves, most of the B horizon soils were characterized by the predominance of permanent negative charges. On the other hand, organic matter contributed to the increase of variable negative charges in the surface soils. The content of organic matter and the percentage of the clay fraction were essential for determining the CEC of the soils of the surface 10 and 30–40 cm depths, respectively. Under the field conditions, the composition of exchangeable cations largely reflected the soil acidity. In addition, the content of organic matter also showed a significant correlation with that of available N in the surface soils. Thus, soil acidity both in the surface soils and subsoils, organic matter content in the surface soils, and clay content in the subsoils were considered to be the main factors that affected soil chemical fertility in the area.     

The effect of wind force with reference to lodging of paddy rice

The lodging of crops is usually caused by wind and/or rain. However, few have studied the influence of wind force in relation to lodging. Grafius (1) blew wind of about 2.6 meters per second on barley plants and oats, and discovered that the moment of force per square centimeter on the leaves and culms was approximately one-fourth that on the heads.