Search Results

You are looking at 21 - 30 of 1,250 items for :

  • Refine by Access: All x
Clear All
Free access

Y.L. Qian, A.J. Koski, and R. Welton

Understanding the possible influence of inorganic soil amendments on salt leaching and deposition is helpful in selecting soil amendments when salinity is a problem. Greenhouse experiments were conducted to: 1) evaluate the effects of isolite and zeolite on turf quality of Kentucky bluegrass (Poa pratensis L.) under three salinity levels; and 2) determine if soil amendments affected leachate composition, salt deposition, and soil sodium absorption ratio (SAR). `Challenger' Kentucky bluegrass was grown in columns filled with 100% sand, 50 sand: 50 isolite, and 50 sand: 50 zeolite (v/v). Irrigation waters with three levels of salinity [0.25 (control), 3.5, or 6.5 dS·m-1] were applied daily for 3 months in Study I and for 6 months in Study II. Saline water reduced turf quality compared with control. Amendment of sand with isolite increased turf quality only during the third month of treatment with the most saline water in Study I. However, zeolite increased turf quality during both the second and third months at both salinity levels in both studies. The beneficial effects of zeolite on turf quality diminished 5 and 6 months after salinity treatments. Amending sand with zeolite reduced leaching of Na+ and K+, but increased the leaching of Ca2+ and Mg2+. Amending sand with zeolite increased SAR values by 0.9, 1.6, and 6.3 units in Study I and 0.9, 3.6, and 10.9 units in Study II, under control, 3.5, and 6.5 dS·m-1 salinity treatments, respectively. Isolite increased SAR by 1.1-1.6 units with 3.5 dS·m-1 and by 2.5-3.5 units with 6.5 dS·m-1 salinity treatments. Results indicate that amending with zeolite may buffer soil solution Na+ concentration in the short-term. In the long-term, however, a substantial amount of Na+ may be retained concurrent with Ca2+ and Mg2+ exchange, thereby increasing sodicity and salinity problems.

Free access

Michael C. Shannon, Catherine M. Grieve, Scott M. Lesch, and John H. Draper

Saline agricultural drainage water may be used as a resource to grow high value horticultural crops and reduce the volume of drainage for eventual disposal. To explore reuse options the effects of salinity and timing of application were tested on selected leafy vegetables grown in 24 sand culture plots in Riverside, Calif. The leafy winter vegetables included `Ruby Red Chard' Swiss chard [Beta vulgaris L. var. flavescens (Lam.) Lam.], `Space' spinach (Spinacia oleracea L.), `Vitamin Green' salad greens [Brassica rapa L. (Narinosa Group)], `Red Giant' mustard greens [Brassica juncea L. (Czerniak)], pac choi [Brassica rapa L. (Chinensis Group)], `Winterbor' kale [Brassica oleracea L. (Acephala Group)], tatsoi [Brassica rapa L. (Narinosa Group)], `Salad King' curly endive (Cichorium endivia L.), and `Red Preco No. 1' radicchio (Cichorium intybus L.). All vegetables were planted at the same time and irrigated initially with tap water and nutrients. At 3 and 7 weeks after seeding (application times), six salinity treatments were initiated by adding salts to the irrigation water to represent the chemical compositions of drainage waters found typically in the San Joaquin Valley, Calif. The six salinity treatments had electrical conductivities of 3 (control), 7, 11, 15, 19, or 23 dS·m-1. A randomized complete block design was used with (6 salinities × 2 application times × 2 replications). Within each plot a 1.5-m row of each of the nine vegetables was grown as split plots. Salinity reduced fresh weight (FW) yields of all species. Salt stress applied at 3 weeks after seeding reduced FWs for seven of the nine vegetables compared to salination at 7 weeks. Analyses of salt tolerance curves, maximum yields, and the point of 50% yield reduction (C50) were conducted. Greens produced the highest biomass at 874 g/plant, but was the most affected by application time. Swiss chard and radicchio were not significantly affected by timing of salinity application, and Swiss chard was the most salt tolerant overall. Greens, kale, pac choi, and to a lesser extent, tatsoi, have potential as winter-grown, leafy vegetables in drainage water reuse systems.

Free access

Nancy Morgan Todd and David Wm. Reed

New Guinea impatiens (Impatiens hawkeri Bull.) were grown in a recirculating ebb-and-flow subirrigation system under increasing levels of salinity stress from a mixture of NaCl and CaCl2 (1:1 equivalent ratio, 2:1 molar ratio) and recommended production levels of other nutrients. Growth and quality decreased as salinity level increased, with a 75% to 80% growth reduction at 18 mol·m-3 NaCl-CaCl2 compared to controls. Among controls, root mass distribution was 10%, 50%, and 40% in the top, middle, and bottom layers of the root zone, respectively. In the highest salinity treatment (18 mol·m-3 NaCl-CaCl2), most of the root mass was in the middle layer (80%), while the root mass in the top and bottom layers was reduced to 5% and 15%, respectively. The electrical conductivity (EC) of the growing medium was high in the top layer in all treatments, but only exceeded maximum recommended levels in the middle and bottom layers in the 4·mol·m-3 or higher treatments. Initial postproduction leaching caused the salts in the top layer to migrate to the middle and bottom layers, which in some experiments induced a rapid and transient wilting. Up to six leaching and drying cycles of a 0.20 leaching fraction were required to reduce EC in all layers to recommended levels. Overall, salable plants of good quality and size were produced with up to 2 mol·m-3 (total 152 mg·L-1) NaCl-CaCl2 in the recirculated nutrient solution.

Free access

C. M. Grieve, J.A. Poss, S.R. Grattan, P.J. Shouse, J.H. Lieth, and L. Zeng

To explore the possibility that saline wastewaters may be used to grow commercially acceptable floriculture crops, a study was initiated to determine the effects of salinity on two statice cultivars. Limonium perezii (Stapf) F. T. Hubb. `Blue Seas' and L. sinuatum (L.) Mill `American Beauty' were grown in greenhouse sand cultures irrigated with waters prepared to simulate saline drainage waters typically present in the western San Joaquin Valley (SJV) of California. Seven salinity treatments were imposed on 3-week-old seedlings. Electrical conductivities of the irrigation waters (EC) were 2.5 (control), 7, 11, 15, 20, 25, and 30 dS·m–1. Vegetative shoots were sampled for biomass production and ion analysis ten weeks after application of stress. Flower stem numbers, length, and weight were determined at harvest. Stem length of L. perezii was significantly reduced when irrigation water salinity exceeded a threshold of 2.5 dS·m–1. Salt tolerance threshold based on stem length for L. sinuatum was 7 dS m-1. The species exhibited significant differences in shoot-ion relations which appear to be related to differences in salt tolerance. Sodium, K+, Mg2+, and total-P were more strongly accumulated in the leaves of L. sinuatum than L. perezii. Both species accumulated K+ in preference to Na+, but selectivity for K+ over Na+ was significantly higher in L. sinuatum than in the more salt-sensitive L. perezii. Chloride concentration in L. sinuatum leaves increased significantly as salinity increased, whereas the 20-fold increase in substrate-Cl had no effect on leaf-Cl in L. perezii. Both Limonium species completed their life cycles at salt concentrations exceeding 30 dS·m–1, a character associated with halophytic plants. Maximum growth of each species, however, occurred under relatively low salt stress, and steadily declined as external salinity increased. Based on this crop productivity response, L. perezii should be rated as sensitive and L sinuatum as moderately tolerant.

Free access

Guiseppe Colla, Youssef Roupahel, Mariateresa Cardarelli, and Elvira Rea

A greenhouse experiment was carried out to determine growth, yield, fruit quality, gas exchange and mineral composition of watermelon plants (Citrullus Lanatus L. `Tex'), either ungrafted or grafted onto two commercial rootstocks `Macis' [Lagenaria siceraria (Mol.) Standl.] and `Ercole' (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) and cultured in NFT. Plants were supplied with a nutrient solution having an electrical conductivity (EC) of 2.0 or 5.2 dS·m–1. The saline nutrient solution had the same basic composition, plus an additional of 29 mm of NaCl. Increased salinity in the nutrient solution decreased total yield. The reduction in total yield in saline treatments compared to control was due to a reduction in the fruit mean mass and not to the number of fruit per plant. Total fruit yield was 81% higher in grafted than in ungrafted plants. The lowest marketable yield recorded on ungrafted plants was associated with a reduction in both fruit mean mass and the number of fruits per plant in comparison to grafted plants. Salinity improved fruit quality in all grafting combinations by increasing dry matter (DM), glucose, fructose, sucrose, and total soluble solid (TSS) content. Nutritional qualities of grafted watermelons such as fruit DM, glucose, fructose, sucrose, and TSS content were similar in comparison to those of ungrafted plant. In all grafting combinations, negative correlations were recorded between Na+ and Cl in the leaf tissue and net assimilation of CO2 Grafting reduced concentrations of sodium, but not chloride, in leaves. However, the sensitivity to salinity was similar between grafted and ungrafted plants and the higher total yield from grafting plants was mainly due to grafting per se.

Free access

D.A. Devitt, R.L. Morris, and L.K. Fenstermaker

We investigated foliar damage to five landscape species sprinkler irrigated with either reuse water or one of five synthesized saline waters that contained elevated single salts mixed with Colorado River water, all having similar electrical conductivities. The experiment allowed us to compare the impact of elevated concentrations of Na, Mg, Ca, Cl, and SO4 on an index of visual damage (IVD), tissue ion concentrations, and spectral reflectance. Waters containing elevated concentrations of MgCl2 or NaCl caused greater foliar damage than did MgSO4, Na2SO4, CaSO4, or reuse water, as recorded in higher IVD values (p < 0.05). Privet and elm were damaged to a greater extent (higher IVD values) than were desert willow, guava and laurel (p < 0.05). Higher IVD values were recorded for all species irrigated with the MgCl2 waters, with mortality recorded in privet. Tissue nutrient concentrations were correlated with the IVD values. In the case of guava, 61% of the variability in the IVD could be accounted for based on N, P and K (P < 0.01). On a treatment basis, the single salts added to the municipal water showed little correlation with the IVD values, except in the case of MgCl2, where Mg was included in the regression equation (r 2 = 0.82, P < 0.01, IVD↑ as S04↓, Mg and P↑). Eleven different spectral indices separated based on treatment and/or species (P < 0.05). In elm, 70% of the variability in the IVD could be accounted for by including Red Edge, Normalized Difference Vegetation Index (NDVI) and Water Band Index (WBI)/NDVI. A mixed response was observed to a post 30-day irrigation rinse in an attempt to reduce IVD values. Based on our results, care should be given to monitoring not only the EC (and osmotic potential) but also the ionic composition when saline waters are blended with other water sources, with the aim of minimizing the concentration of Mg, Cl, and Na.

Free access

Kenneth B. Marcum and Mohammad Pessarakli

( Barnett et al., 2005 ; Pearman et al., 2003 ). Demand on limited potable water resources is resulting in government-mandated water use restrictions, which limit use of potable water while requiring use of reclaimed or other secondary saline water sources

Free access

Joseph G. Robins, B. Shaun Bushman, Blair L. Waldron, and Paul G. Johnson

with sufficient salinity tolerance ( Alshammary et al., 2004 ). Additionally, large areas of the world are characterized by soils with high levels of salt. Oldeman et al. (1991) estimated that ≈80 M ha of arable soil is salt-affected worldwide. Thus

Free access

Chenping Xu and Beiquan Mou

Salinity of soil and irrigation water is a growing problem for agricultural production in the world. It is estimated that salt-affected soils impact on nearly 10% of the land surface and 50% of irrigated land in the world ( Ruan et al., 2010

Free access

Yiming Liu, Hongmei Du, Kai Wang, Bingru Huang, and Zhaolong Wang

Salinity is one of the major abiotic factors limiting plant growth in many areas of the world, which is progressively increasing as a result of the decline in fresh water for irrigation and increasing use of effluents that contain concentrations of