Raul I. Cabrera

Monitoring chemical properties of container growing media with small soil solution samplers

Abstract Soil solution samples from peat-based growing media, irrigated with different nutrient solutions, were extracted at container capacity with small hydrophilic polymer soil moisture samplers (SMS), analyzed for pH, electrical conductivity (EC), NO3–N and NH4–N, and evaluated against results obtained by saturated media extract (SME) and pour-through (PT) procedures. The correlation between applied and extractable NO3–N, NH4–N and EC was excellent (r2>0.98) for all methods. Values from SMS were statistically similar to those from PT, whereas those obtained by SME were significantly lower. In contrast to the above mentioned chemical parameters, pH readings among extraction procedures were less correlated and more variable, particularly in a peat:perlite medium. Simplicity of use, non-ion exchange properties, low cost and good potential longevity make SMS promising monitoring tools for container crop production and mineral nutrition research.

Nitrogen‐form and endophyte‐Infection effects on growth, nitrogen uptake, and alkaloid content of chewings fescue turf grass

Abstract Chewings fescue (Festuca rubra L. ssp. commutata Gaud) is naturally infected by an endophyte, however, little is known about the biology of this association and the effects on host fitness. A hydroponic study was conducted in the greenhouse to determine if endophyte and/or nitrogen (N) form influenced growth, N accumulation and alkaloid production in ‘Jamestown II’ Chewings fescue. Endophyte‐infected and non‐infected grasses were established in solution culture for 5 weeks using a 1/4 strength modified Hoagland solution, and then grown for 15 d in similar solutions containing 50 mg L‐1 of N as either NH4‐N, NO3 ‐N or a 1:1 mixture of NH4‐N and NO3 ‐N. The presence of the endophyte increased total biomass 54% in this grass, but growth was unaffected by N source. Nitrogen uptake was 58% higher in endophytic grasses, but no differences were observed in N use efficiency with respect to non‐endophytic grasses. Nitrogen form affected both N uptake and N use efficiency, with significantly higher values ...

Enhancement of short-term nitrogen uptake by greenhouse roses under intermittent N-deprivation

A recirculating nutrient solution system was utilized to study the effect of intermittent N deprivation on N uptake by mature ‘Royalty’ rose over the course of one flowering cycle.Plants received a nutrient solution lacking N for 4, 8 or 16 days, after which one containing NO3−N (0.75 mM) was supplied for 4 days. N-deprivation resulted in a 2–3 fold increase in N uptake rate compared to control plants supplied continuously with N. The magnitude of this deprivation-enhanced N uptake was not affected by either the duration of N-deprivation or the plant developmental stage. Over the course of the flowering cycle, the total cumulative N uptake by the plants was 95, 66, and 44% of the control plants in the 4, 8 and 16-day deprivation treatments, respectively. A characteristic diurnal pattern of N uptake occurred in both N-starved and control plants. Uptake oscillated between minimum rates in the morning and maximum rates in the evening, the latter occurring 4–6 hr after the maximum rate of transpiration.

Mineral Nutrition and Fertilization Management

Mineral nutrition knowledge and fertilization management practices in the production of rose crops have evolved significantly in the last century, going from an organic and rudimentary methodology based in mineral soils to modern, technologically advanced nutrient delivery systems based on soilless growing media and hydroponics. This article addresses some of the key advances in these topics. While primarily addressing greenhouse-grown rose crops for cut-flower production, some of the information covered here can apply to intensively managed garden and landscape rose plantings.

Moisture and Nutrient Storage Capacity of Calcined Expanded Shale

Expanded shale (EXSH) is an important and increasingly popular soil conditioner with several horticultural applications, including its use as a soil amendment for clay textured soils (Sloan et al., 2002), as an ingredient in plant growing media (Sloan et al., 2010) or green roof substrates (Ampim et al., 2010 ). It is a lightweight material produced by firing mined lumps of shale at high temperatures in a rotary kiln in a process similar to that of clay ceramics. The resulting product can be screened to create various size fractions depending on the intended use. For example, Texas Industries (TXI) of North Texas, USA produces five size fractions of expanded shale that includes the following ranges, from smallest to largest, 0.07 to 0.60 mm, 0.60 to 2.0 mm, 2.0 to 4.8 mm, 4.8 to 6.4 mm, 6.4 to 9.5 mm, 9.5 to 12.7mm, 12.7 to 15.9 mm Expanded shale aggregates are suitable as components of planting media and soil amendments because, unlike most minerals, they are porous, stable, and resistant to decomposition (Ferguson, 2005). Expanded shale is believed to beneficially modify growth media properties by enhancing overall aeration, improving water and nutrient holding and release capacities, and promoting optimum plant growth (Blunt, 1988; Dunnett and Kingsbury, 2008). Sloan et al. (2002) found that expanded shale consistently improved overall plant performance better than quartz sand, sphagnum peatmoss and cottonseed hull when they were used as amendments for poorly-drained Austin silty clay soils suggesting its superiority as a soil conditioner for the production of horticultural crops on soils with poor tillage characteristics. In a similar way, Nash et al. (1990) found that a potting medium comprising a mixture of peat moss and expanded shale increased the growth and quality of petunia and impatiens. Smalley et al. (1993) also found that amending soils with products containing expanded shale did not hamper plant performance. Though growth index and plant dry weight of Salvia (Salvia splendens) and Vinca (Catharanthus roseus) increased with increasing fertilizer levels for all their treatments, the greatest performance of these plants were observed for treatments amended with the product containing expanded shale, granite sand and composted poultry litter. In another application, Forbes et al. (2004 and 2005) discovered that expanded shale is a potential sorbent for phosphorus in subsurface flow