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Shivani Kathi, Catherine Simpson, Alinna Umphres, and Greta Schuster

because the increased yield per unit of added N diminishes as total N supply approaches the yield-maximizing level (i.e., Law of Diminishing Returns) ( Bhattacharya, 2019 ; de Wit, 1992 ). In addition to N uptake efficiency issues, leaching is another

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Catherine S. M. Ku and David R. Hershey

Single-pinched `Yours Truly' geranium (Pelargonium × hortorum) were greenhouse grown in 15-cm diameter pots. They received constant liquid fertigation with a modified Hoagland solution #1 at 0.25, 0.5, 1.0, and 1.5 strength. The 1.0 strength Hoagland solution contained 210 mg/L NO3-N and 31 mg/L P. Leaching fractions (LFs) were 0, 0.2 and 0.4. The total P applied via fertigation ranged from 33 mg at 0 LF and 0.25x Hoagland to 407 mg at 0.4 LF and 1.5x Hoagland. The leachate P concentration ranged from <5 mg/L to -60 mg/L. The P concentration in the recently matured leaves was in the acceptable range for all treatments. We were able to recover 90 to 99% of the applied P by analyzing the shoots, soilless medium, and leachate. Only 4% of the recovered P was in the leachate for plants receiving 0.5x Hoagland and a 0.2 LF. However, these plants were equal in yield to plants receiving higher fertigation rates and higher LFs.

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Clyde W. Fraisse, Zhengjun Hu, and Eric H. Simonne

production (as a response to a low probability of leaching rainfall occurrence) and, conversely, if a high probability in leaching rain occurrence would justify an increase in fertilization recommendation. Ultimately, as illustrated in the wheat and canola

Open access

T. H. Yeager and J. E. Barrett

Abstract

Polyvinyl chloride columns (4 × 15 cm) containing by volume either 2 pine bark : 1 moss peat : 0 sand, 2 pine bark : 0 moss peat : 1 sand, 0 pine bark : 1 moss peat : 1 sand, or 2 pine bark : 1 moss peat : 1 sand amended with 3 kg m-3 of 32P-superphosphate (8.7% P) were leached daily with 16 or 32 ml of deionized water (pH 5.5) in 1 hour. Irrigation rate did not affect 32P leaching nor was there a media rate interaction or difference in the percentage total 32P and dissolved 32P leached. Medium 2:1:1 had the greatest percentage (76%) of 32P leached during the 3-week experimental period, however, 55% of the 32P amendment leached from each medium the 1st week.

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Rangjian Qiu, Yuanshu Jing, Chunwei Liu, Zaiqiang Yang, and Zhenchang Wang

when irrigated with saline water, with an adverse effect on fruit yield ( Ben-Gal et al., 2008 ; Munns, 2002 ). To alleviate the effects of salinity stress on plants, the application of extra water for the leaching of salts (e.g., Na + , Ca 2+ , and Mg

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Jeff B. Million, Thomas H. Yeager, and Joseph P. Albano

irrigation demand. Beeson (2006) found that 20% MAD produced acceptable sweet viburnum growth. By minimizing leaching volume, ET-based irrigation has the potential to reduce nutrient leaching losses during production and, therefore, allow smaller quantities

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J.P. Syvertsen, M.L. Smith, and B.J. Boman

Effects of salinized irrigation water on tree canopy and root growth, water use, foliar nutrition, and leaching losses below the rootzone were studied during a 2-year period using single tree lysimeters. Eighteen 6-year-old `Valencia' orange trees on either Carrizo citrange (CC) rootstock or sour orange (SO) rootstock were each transplanted into 7.8 m3 drainage lysimeters and irrigated with water having an electrical conductivity of 0.3, 1.6, or 2.5 dS m-1 from a 3:1 ratio of NaCl:CaCl2. Six additional trees (3 on each rootstock) were transplanted into soil without tanks. Trees outside the tanks were smaller, but nutritionally similar to the low salinity trees in lysimeters. Trees on CC were larger, had greater root densities, and were associated with less leaching of ions and nutrients into drainage water from the tanks than trees on SO. High salinity irrigation water reduced canopy growth and ET, but increased fibrous root dry weight. Trees on CC accumulated more Cl in leaves and in fruit juice than those on SO. Leaching loss of total N varied from 2-8% of that annually applied to trees, but up to 70% of the applied N and up to 80% of the applied K were leached from the blank tank with no tree. Salinized trees lost more N and K to drainage water, especially those on SO. Tree size, root density, and irrigation water quality can influence leaching losses beyond the rootzone.

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Rachid Mentag, Isabelle Duchesne, and Jacques-André Rioux

The objective of this study was to determine the persistence and leaching of the herbicide oxadiazon in five substrates. The substrate mixtures consisted of the following: peatmoss, compost, and sand in the following proportions: 1:1:0, 3:3:2, 1:1:2, 1:1:6, and 0:0:1 in 5-liter containers. Rates of oxadiazon used were 4 and 8 kg a.i./ha on two separate split-split plots. Each experimental design had three factors: five substrates, four harvest times (24 h; 1, 2, and 3 months) and five soil depths (0–2, 2–4, 4–6, 6–8, 8– cm). Only herbicide persistence and leaching from the various substrates were investigated in this experiment; therefore, we did not remove plant material. Substrate oxadiazon residues were determined by gas chromatography analysis, and it was shown that leaching was more evident in media with a lower percentage of organic matter. In addition, oxadiazon did not leach below 4 cm in conventional substrate (1 peatmoss: 1 compost: 1 sand, respectively). The persistence of oxadiazon was affected by soil composition and herbicide persisted more in substrates with great percentage of organic matter.

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Yingqian Lin, Alexa R. Wilson, and Pascal Nzokou

). For example, the incorporation of cover crops has proven to significantly reduce nitrate leaching in rubber tree plantations ( Schroth et al., 2001 ) and in cereal grass-based systems where they are reported to be more efficient in the uptake of

Open access

Robert P. Wiedenfeld and Edward L. Cox

Abstract

Ground limestone (CaCO3) was applied at 0, 25, 50, 75, or 100 g/9.5-liter pot using a 1 peat : 1 perlite : 1 vermiculite (by volume) medium having an initial pH of 4.52 and an electrical conductivity (EC) of 0.2 dS·m–1. Muskmelon (Cucumis melo var. reticulatus) were grown for 56 days in the medium that had been fertilized. Irrigations were applied as the crop grew, with the levels used consisting of 0%, 20%, 40%, or 60% in excess of the amount required to bring all pots to saturation. The water had a pH of 7.44 to 7.95 and an EC from 1.5 to 1.8 dS·m–1. Measurements were taken at each irrigation. Leachate pH increased with increasing rate of limestone application, but the rate of increase with increasing limestone rate declined, with maximum benefit occurring at 75 g/pot. Irrigtation level did not affect leachate pH, which indicates a buffering capacity of the medium that was not readily diluted. Increasing limestone application decreased leachate EC, which suggests retention of the salts from the irrigation water. This retention resulted in a net accumulation of salts in the medium that could not be completely offset by the increased leaching produced as irrigation levels increased.