George H. Snyder

Silicon Management and Sustainable Rice Production

Publisher Summary Rice is a Si accumulator; therefore, adequate attention should be given to the beneficial role that Si nutrition and its management can play in a balanced integrated nutrient management system for increasing and sustaining rice yields. Large amounts of Si as monosilicic acid [H 4 SiO 4 , or Si(OH) • 4 ] are absorbed by the rice plant. Subsequently, Si is deposited as amorphous SiO, and is mainly associated with cellulose and hemicellulose in the rice plant tops (leaves and hulls) in the form of so-called cuticle-Si double layer. The solubility of soil Si is low. Si in soil solution (intensity factor) is largely influenced by its dissolution kinetics, which in turn is influenced by various soil factors such as Al, Fe oxides, organic matter, redox potential, and moisture. This chapter summarizes the past and current literature on Si nutrition of rice. A Si management agenda is presented, and its potential beneficial role in increasing and sustaining rice productivity in the future is discussed. A few suggestions for future research on Si are indicated that should help to meet a critical need for Si to increase rice yields on a sustained basis.

Silicon nutrition and sugarcane production: A review 1

Abstract Silicon (Si) is one of the most abundant elements found in the earths crust, but is mostly inert and only slightly soluble. Agriculture activity tends to remove large quantities of Si from soil. Sugarcane is known to absorb more Si than any other mineral nutrient, accumulating approximately 380 kg ha−1 of Si, in a 12‐month‐old crop. Sugarcane (plant growth and development) responses to silicon fertilization have been documented in some areas of the world, and applications on commercial fields are routine in certain areas. The reason for this plant response or yield increase is not fully understood, but several mechanisms have been proposed. Some studies indicate that sugarcane yield responses to silicon may be associated with induced resistance to biotic and abiotic stresses, such as disease and pest resistance, Al, Mn, and Fe toxicity alleviation, increased P availability, reduced lodging, improved leaf and stalk erectness, freeze resistance, and improvement in plant water economy. This review ...

Silicon fertilization for disease management of rice in Florida

Abstract Although silicon is not considered an essential element; plant development, growth and yield has been increased in many graminaceous and some nongraminaceous crop species. Silicon also is known to reduce plant diseases especially in rice. Silicon fertilization has become a routine practice in Florida rice production. The information within provides an overview on the history of silicon in Florida, application of silicon and disease suppression by silicon and its interaction with fungicides and rice genotypes. Although the focus is on rice and organic soils, this information should be of interest to those working on other grass crops on organic soils as well as rice production on weathered, low-silicon mineral soils. An outlook and future research needs also are presented.

Depletion of plant-available silicon in soils : A possible cause of declining rice yields'

Abstract The phenomenon of yield decline in different rice ecosystems from many parts of the world has been reported to be associated with decreases in the effective nitrogen (N) supply from soil. However, many reports in the literature suggest that silicon (Si) is an agronomically essential element for sustainable rice production. Depletion of plant‐available Si in soils where rice is grown could be a possible limiting factor contributing to declining yields. In order to address this problem of yield decline or stagnation, it seems necessary to survey Si status of soils and rice grown in different ecosystems throughout the world and develop region‐specific integrated nutrient management systems that include the element Si.

CALIBRATION OF SOIL AND PLANT SILICON ANALYSIS FOR RICE PRODUCTION

Calibration of field crop response to nutrient availability is the bases for making a fertilizer recommendation from soil and tissue analyses. The purpose of this study was to evaluate and summarize results from a series of experiments on silicon (Si) fertilization of rice in the Everglades Agriculture Area. Twenty-eight rice field experiments were conducted from 1992 through 1996. The experiments consisted of 2 to 5 rates of calcium silicate applied to soils (Histosols) of varying Si soil-test values. Soil samples were taken before planting and analyzed for acetic acid (0.5 mol L−1) extractable Si. Straw samples were collected at harvest and analyzed for total Si. Grain yield was determined. The “critical” levels for Si in the soil (point below which response to Si fertilizer is expected) calculated by the Cate & Nelson procedure was 19 mg Si L−1 soil. The amount of silicon to correct Si deficiency in the soil and to obtain optimum rice yield was 1500, 1120 and 0 kg ha−1 for low (<6 mg L−1), medium (6 to 24 mg L−1), and high (>24 mg L−1) level of soil Si, respectively. Silicon in the straw was classified as high when Si concentration was >34 g kg−1, medium when in between 17 and 34, and low when <17 g kg−1 (3.4 and 1.7%, respectively). *Florida Agricultural Experiment Station Journal Series No. R-06752.

Variable silicon content of rice cultivars grown on everglades histosols 1

Abstract Two experiments were conducted to investigate silicon (Si) content in a group of rice cultivars. Ten cultivars were grown in the greenhouse under three levels pf Si fertilization on a Si‐deficient Histosol. In a second experiment, 18 ‘cultivars were grown at three field locations which varied in plant‐available soil Si. In both experiments, cultivars varied in their percentage of Si in rice straw. There was no significant (P > 0.10) genotype by environment interaction. The genotypes with the greatest and lowest percentage of Si were consistently so over all Si environments and treatments.

Chapter 11 Methods for silicon analysis in plants, soils, and fertilizers

The classical method for determining total silicon (Si) content of various materials has been conversion of insoluble silicates into sodium silicate through high temperature fusion with sodium hydroxide, or other sodic bases. The Si can then be determined by a variety of methods, including gravimetric, colorimetric, and absorption/emission spectrometry. Silicon also has been determined gravimetrically in plant tissue as the residue after acid digestion. We have developed a simple inexpensive, and rapid method for solublizing Si in plant tissue that facilitates analysis of a large number of samples. When analyzing soils and fertilizers, a method for gauging the plant-available Si, rather than total Si, generally is desired. A number of soil-test methods have been developed. Some require extended incubation periods, field-moist soil, or other procedures that inhibit adoption by routine soil-testing laboratories. Silicon extracted by acetic acid has been correlated to Si uptake by rice (Oryza sativa L.) and rice grain yield. Using this method, the Everglades Soil Testing Laboratory analyses nearly five thousand samples annually. Since Si fertilizer sources differ in Si content and Si solubility, analytical methods have been developed for predicting their relative ability to provide plant-available Si. We use a column leaching method based on Si elution in Tris buffer (pH 7) for the evaluation of potential Si soil amendments. However, greenhouse and field evaluations are essential for making final determinations.

Leaf‐tissue silicon content of sugarcane genotypes grown on everglades histosols 1

Abstract On soils low in plant‐available silicon (Si), fertilization of sugarcane (Saccharum spp.) with calcium silicate slag increases plant Si content and sugar yield. However, Si fertilization is costly. Plants which are more efficient in accumulating available Si may have an economic advantage, and selection for genotypes with greater Si content may be warranted. The purpose of this study was to determine if there was genetic variability for plant‐tissue Si content in selected populations of commercial‐type sugarcane clones in the Canal Point (CP), Florida breeding program. A total of 52 sugarcane genotypes from the third and fourth stages of the sugarcane breeding program were evaluated for Si content in leaves. Clones were evaluated as plant cane in randomized complete‐block experiments at four sites which varied in plant‐available Si. Soils at three sites were organic Histosols; the fourth was a sand. The locations and the forty Stage HI clones varied significantly (P<0.01) in plant‐tissue Si. Stag...

INFLUENCE OF SILICA ON GROWTH, QUALITY, AND WEAR TOLERANCE OF SEASHORE PASPALUM

Wear is a predominant stress affecting growth of turfgrass. Silica, which is deposited in epidermal cells of leaf blades, may potentially increase rigidity of a turfgrass stand. This research was undertaken to determine if application of silicon (Si) would enhance turfgrass wear tolerance, growth, and quality. This research was conducted during two consecutive field trials in 1998 on two greens-quality ecotypes established on a native Applying (Typic Kanhapludult) soil at the University of Georgia Experiment Station in Griffin, GA. Silica was applied to two ecotypes of seashore paspalum (Paspalum vaginatum Swartz.) as potassium (K) silicate at two foliar rates (1.1 and 2.2 kg Si ha−1) and as a soil drench rate of 22.4 kg Si ha−1. Potassium chloride, which added K at the amount in the drench treatment (15.6 kg K ha−1), was also applied as a K check. Best turf quality responses on nonwear plots resulted from highest rates of Si application as well as from the K only treatment. A positive association was found between leaf tissue K concentration and turf quality scores, while increasing Si concentration reduced quality scores. Wear tolerance was enhanced either by K alone or by the high rate of Si and K. Turf growth was not affected by fertility treatments. Enhanced wear tolerance, due to application of either K alone or Si and K, reduced wear injury from 35% to 14% (K) or 20% (Si and K) averaged across both studies. This may be attributed to increased leaf turgor pressure or reduced total cell wall (TCW).

Evaluation of soil test procedures for determining rice-available silicon

Soil testing for silicon (Si) in the predominantly organic soils of the Everglades Agricultural Area has not been sufficiently investigated. The objective of this study was to identify a suitable Si extraction method for these soils for rice (Oryza sativa L.). Twenty-two surface soil samples were collected from 10 farms. Of these 22, 10 samples were from fields that had received Si fertilization at some time in the past, and 12 were from fields that had not received Si fertilization. Rice was grown for 80 days in each soil in the greenhouse. Subsequently, the straw and immature panicles were harvested, dried, weighed, and analyzed for Si. In the laboratory, seven different methods were used for extracting Si from the soils. The methods were: (1) 0.5 M acetic acid extract, 10:25 (soil:extract, v/v ratio), (2) citric acid 1%, 1:10, (3) demineralized water, 1:10, (4) TRIS buffer pH 7.0, 1:10, (5) water-bath shaking (Batch method) 1:10 v/v ratio plus cation exchange resin (Amberlite IRC-50 H type), (6) soil incubated with water for 1 week at 40°C, 1:6 (Incubation method), and (7) soil incubated with water for 4 weeks at 30°C, 1:4 (Extended Incubation method). The concentration of dissolved Si in soil extracts from all methods was determined colorimetrically. Soil Si values were correlated with straw Si and panicle Si content. Among the methods studied, extraction with 0.5 M acetic acid appeared most suitable for evaluating Si availability, followed by extraction with citric acid at 1%. These methods provided the best correlations with rice straw and panicle Si percentage (r2 = 0.899***, r2 = 0.768***, and r2 = 0.839***, r2 = 0.774*** respectively). These methods, being rapid and effective in extracting Si in comparison to other methods, appear to be the most suitable for routine soil testing for Si in the Everglades Agricultural Area in South Florida.