S. Miyamoto

Salt and Specific Ion Effects on Germination of Four Grass

Highlight: The effects of NaCI, CaCl2, MgCl2, NaSO4, CaSO4 2H2O, and MgSO4 7H20 at concentrations of 50, 100, 150, and 200 meqll were studied on germination of the following range grasses: blue panicgrass (Panicum antidotale Retz.), Lehmann lovegrass (Eragrostis lehmanniana Nees.), Wilman lovegrass (E. superba Peyr.), and weeping lovegrass (E. curvula (Schrad.) Nees.). Increasing salt concentrations decreased germination. The extent of the decrease varied with the species and the type of salt. Inhibition was greatest with Mg and least with Ca salts. When MgSO4- 7H2 0 was used, the effect was less than the equivalent concentration of MgC92. At equal osmotic pressures the effect of specific ions varied. Wilman and wveeping lovegrasses were found to be relatively salt tolerant. Economic viability of ranching depends largely upon increasing pasture output of extensive grazing areas. The introduction of nonindigenous grass species has been heralded as a major advance. Lovegrasses introduced from South Africa are good forage producers and suitable for the climatic conditions of the Southwest at lower elevations (Humnphrey, 1960). With good management, these grasses can be used for revegetation of depleted ranges as well as for prevention of soil erosion from embanktnents such as road and railways. Mine tailings have been revegetated successfully with some of these grasses (Ludeke, 1973). Blue panicgrass (Panicum antidotale Retz.)

Salt effects on germination and seedling emergence of several vegetable crops and guayule

SummarySalt effects on seed germination and seedling emergence of several crops are evaluated to understand poor plant stands occurring in furrow-irrigated fields in saline areas. The test crops were carrot (Daucus carota L. cv. Imperator 58), chile pepper (Capsicum annuum L. cv. New Mexico 6-4), tomato (Lycopersicon esculentum M. cv. Rutgers), and guayule (Parthenium argentatum G. cv. 593). Seed germination was measured in petri-dishes containing saline solutions (0.8 to 32 dSm−1 with a Na to Ca + Mg ratio of about 2 : 1); and seedling emergence in potted fine loamy sand subirrigated in a greenhouse with saline waters (0.8 to 7.6 dSm−1 with SAR < 16). Seedling emergence through a thin layer of salted-loamy sand (having ECeup to 46 dSm−1) placed on emerging seedlings was also evaluated. Germination of tomato and carrot seeds began to decline at solution salinities of 12 and 18 dSm−1, respectively, and was virtually zero at 23 dSm−1, Chile pepper and guayule germinated well at 23 dSm−1, Tomato had the highest emergence, and guayule the lowest, showing less than 20% when subirrigated at 2.2 dSm−1, Seedling emergence which increased in the order of guayule, carrot, chile pepper and tomatoes did not quantitatively correlate with seed germination. However, it did correlate with the emergence through the thin layer of the salted-sand placed over emerging seedlings except in tomato. Salinity of the saturation extract of the surface 5 mm soil increased to 21 and 31 dSm−1, in 7 days when subirrigated with water of 4.3 and 6.4 dSm−1, respectively. Poor seedling emergence of guayule, carrots and, to some extent, chile pepper appeared to be caused by hypocotyl mortality associated with the salts accumulated at the soil surface, but not by reduced seed germination. The control of surface accumulated salts should be the target of management for improved emergence of these crops.

Effects of saline water irrigation on soil salinity, Pecan tree growth and nut production

SummaryIrrigated cultivation of pecans (Carya illinoensis K.) has increased dramatically in the Southwestern USA, yet their tolerance to salinity remains largely unknown. The first part of this study was conducted to assess if stunted tree growth reported in clayey soils is related to salinity, and the second part was to evaluate changes in soil salinity and the performance of 11 year old ‘Western’ trees irrigated with water of 1.1 dSm−1 and 4.3 dSm−1 for 4 years. The first study, conducted at a commercial orchard (49 ha) in the El Paso valley (TX), showed a highly significant correlation between tree trunk size and salinity of the saturation extract (ECe) with r=−0.89. Soil salinity above which trunk size decreased in excess of the standard error was 2.0 dSm−1 in ECe from 0–30 cm depth, and 3.0 dSm−1 in 0 to 60 cm depth with corresponding Na concentrations of 14 and 21 mmol l−1. Excessive accumulation of salts and Na was found only in silty clay and silty clay loam soils. The second study, conducted at a small experimental field (1 ha), indicated that irrigation with waters of 1.1 and 4.3 dSm−1 increased ECe of the top 60 cm profile from 1.5 to 2.2 and 4.2 dSm−1 and Na concentration in the saturation extract to 17 and 33 mmol l−1, respectively. The leaching fractions were estimated at 13 and 37% when irrigated with waters of 1.1 and 4.3 dSm−1, respectively. Tree growth progressively slowed in the saline plots irrigated with water of 4.3 dSm−1, and became minimal during the 4th year. The cumulative shoot length over the 4 year period was reduced by 24% and trunk diameter by 18% in the saline plots relative to nonsaline plots. Irrigation with the saline water also reduced nut yields by 32%, nut size by 15% and leaflet area by 26% on the 4 year average, indicating that pecans are only moderately tolerant to salinity. The concentration of Na, Cl and Zn in the middle leaflet pair did not differ significantly between the two treatments. Soil salinity provided a more reliable measure for assessing salinity hazard than leaf analysis. However, soil salinity was found to be highly spatially variable following a normal distribution within a soil type. This high variability needs to be recognized in soil sampling as well as managing irrigation.

Dissolution rate of gypsum in aqueous salt solutions

We measured the dissolution rate of gypsum particles (0.5− to 1.0-mm fraction) in distilled water and in aqueous salt solutions of NaCl, MgCl2, Na2SO4, MgSO4, and CaCl2 at salt concentrations of 20, 40, and 60 mmol kg−1. Two gypsum samples were tested, one from a gypsum mine in Egypt and another from New Mexico, United States. We monitored the dissolution rate by measuring Ca concentrations in these solutions with and without shaking. The rate of gypsum dissolution increased with shaking and with increasing concentration of the salt solutions. Neither ion concentration nor species influenced the rate of gypsum dissolution when the rate was normalized by the solubility. The first-order reaction equation was unsuited for describing the dissolution process when Ca concentrations exceeded about 50% of gypsum solubility. The second-order reaction equation described the process well, providing a rate constant independent of ion concentrations or species.

SULFURIC ACID AND LEACHING REQUIREMENTS FOR RECLAIMING SODIUM-AFFECTED CALCAREOUS SOILS*

SummaryThe changes in exchangeable sodium and total dissolved salts due to the application of sulfuric acid and water to sodium-affected calcareous soils were studied for the purpose of establishing a convenient way of determining acid and leaching water requirements. Conventional methods which ignore the effect of sodium removed from soil exchange sites are inadequate for estimating amounts of acid needed to obtain a desired level of exchangeable sodium, especially at high acid application rates. Modified equations are presented which predict the changes in exchangeable sodium and total dissolved salts using essentially the same input data needed for conventional methods, and appear advantageous for estimating acid and leaching water needs.

Water quantity and quality requirements of guayule: Current assessment

Abstract Because of the stragetic and industrial importance of natural rubber, there is renewed interest in cultivating guayule (Parthenium argentatum) in the Southwestern U.S.A. and several other arid regions of the world. This review was made to assess the quantity and quality of water required to cultivate this crop under irrigation. Data from Arizona and West Texas show that under high transplant densities (44 000 to 54 000 plants per ha), shrub and rubber yields increase almost linearly with increasing irrigation up to 300 cm for the first 2 years. The amount of water required to produce a ton of dry shrub in 2 years ranges from 1200 to 1600 m3 for a wide range of irrigation regimes and irrigation water salinity. Although rubber content in the shrubs increases with increasing water stress, the increase is generally insufficient to offset the reduction in shrub yield under high plant densities. Salinity stress may increase rubber content slightly, but reduces shrub and rubber yields when salinity of irrigation water exceeds 4 to 6 dS m−1 in sandy soils. The amount of water required to produce 1 kg of rubber with existing cultivars (with rubber contents of 40 to 70 g kg−1) ranges from 20 to 30 m3, and should decrease substantially with the development of cultivars with higher rubber contents. The resin content in the shrubs does not change greatly with irrigation or salinity levels, thus the resin yield increases proportionally with shrub yield or irrigation amount. If guayule is to be established through direct seeding, additional water of low salinity needs to be allocated. Nursery grown seedlings have been transplanted successfully in spring months with 10–25 cm of water having salinity less than about 4 dS m−1. If high rubber yields are to be achieved in 2–3 years, water requirements for guayule would be comparable to those for alfalfa. However, guayule can be grown with less quantities of water because of its high drought tolerance, especially when rubber production is the sole purpose.

Relation of solute and sorbed boron to the boron hazard in irrigation water

SummaryThe current criteria for evaluating the boron (B) hazard of irrigation water for specified crops are based on the concentration of B in the irrigation water without consideration of soil properties or the leaching fraction. Experiments were conducted to determine the influence of B sorption capacity on plant uptake of B at rates of 0.1, 2.5, 5.0 and 10.0 ppm B in the irrigation water with a leaching fraction of 0.5. A relatively B sensitive crop, oats (Avena sativa), was grown on four arid-region soils of varying B sorption capacities. The results show that B in solution rather than sorbed B influenced B toxicity.

Solubility of manganese, iron, and zinc as affected by application of sulfuric acid to calcareous soils

SummaryFour calcareous Arizona soils were treated with sulfuric acid applied to varying degrees of saturation of the acid titratable basicity of the soils. At less than 100% saturation there was a significant increase in water soluble Mn and in DTPA extractable Fe and Mn compared with untreated soil. Only when the acid treatment exceeded 100% ATB did a significant increase occur in the water soluble forms of Fe and Zn. The amounts of the Fe and Zn extracted increased with the rate of application and with time of soil/acid contact at the higher level of acidification.

Comparative effects of chemical amendments on salt and Na leaching.

SummaryEfficiency of sodic soil reclamation is thought to vary with types of chemicals used. This study examined the effects of five inorganic (H2SO4, CaCl2 · 2H2O, CaSO4 · 2H2O, FeSO4, Al2(SO4)3) and two organic compounds (polyacrylamide, and trihydroxy glutaric acid) on the rate and the extent of salt and Na leaching in moderately Na-affected saline soils: Saneli silty clay loam (Vertic Torrifluvents, ESP=17.5%) and Glendale silty clay (Typic Torrifluvents, ESP=13.5%). Air-dry soil samples (<2mm) were packed in columns, and chemicals, except H2SO4, were incorporated into the surface 5 cm of the soils, and in selected cases, to 30 cm. H2SO4 was surface-applied. Application rates of the inorganic chemicals were 3.57 and 10.7 mmol(+) kg-1 (2.5 and 7.5 Mg ha-1 in gypsum equivalent weight) in the silty clay loam, and 8 and 24 mmol(+) kg-1 in the silty clay, and the organic compounds were applied at rates of less than 620 kg ha-1. The soils were then leached with simulated Rio Grande water (EC = 1.1 dS m-1, SAR = 3.5) under continuous ponding. The tested inorganic compounds removed approximately equivalent amounts of exchangeable Na after approximately 35 cm of water application. However, the rate of water percolation (consequently the rate of salt leaching) from CaCl2 treated columns, became progressively slow after about 20 cm of water intake. The combined effect of rapid electrolyte leaching and insufficient replacement of Na in the surface layer seemed to be responsible for the flow reduction. Gypsum and H2SO4 treatments provided lower ratios of sodicity to salinity in percolating solutions and relatively uniform hydraulic gradients throughout the soil depth. Incorporation of chemicals to the surface 30 cm did not alter performance, except in CaCl2 treatments where water intake rates became even slower. The tested organic amendments improved initial water infiltration, but neither increased subsequent percolation rates nor improved salt and Na leaching. The fastest reclamation may be attained when chemicals are chosen and applied to yield an electrolyte concentration that is high enough to overcome Na effects at any depth of soil profiles throughout the leaching period.

Effects of wetting agents on water infiltration into poorly wettable sand, dry sod and wettable soils

SummarySix commercial wetting agents (three nonionic and three anionic compounds) were tested for their effects on water infiltration into poorly wettable sand, a layer of dry bermudagrass sod, and two wettable soils. The poorly wettable sand and the sod of dormant bermudagrass were obtained from an old lawn area, and the wettable soils (silty clay, and saline sodic silty clay loam) from a pecan orchard and a cotton field. The infiltration of tap water (salinity of 0.8 dS m−1 and a sodium adsorption ratio of 5) was measured in laboratory columns using air-dried soil (or sod) samples after initial soil application of wetting agents at rates equivalent to 12 and 24 L ha−1. The stem of the dormant bermudagrass exuded a brownish substance, and was found to be strongly water-repellent. Application of wetting agents markedly improved initial water infiltration into both the poorly wettable sand and the sod. The effect persisted for the entire test period of four irrigations using a total of 10 cm of water. Effectiveness, however, varied significantly among the tested compounds: polyoxyethylene glycol, polyethylene glycol ether and sulfosuccinate compounds were more effective than linear sulfonate or ethoxolated alcohol. The water-repellency of the poorly wettable sand was reduced substantially without wetting agents after two irrigations (using 5 cm of water), and that of the dormant sod after three irrigations (7.5 cm of water). Water infiltration into the air-dried wettable soils also increased significantly in the 1st irrigation (using 10 cm of water) showing 10 to 25% reductions in infiltration time with the application of polyoxyethylene glycol and polyethylene glycol ether.