Abstract
Seedlings of ‘Lovell’ and ‘Elberta’ peach [Prunus persica (L.) Batsch] were grown in the greenhouse for 29 or 50 days in nutrient solutions containing 8, 16, 33, 66, 132, 264, or 660 µM Ca at pH 4.5. Relative growth rate was unaffected by Ca concentrations. Calcium concentration in the stems was increased from 700 to 4330 µg/g dry weight and in the roots from 348 to 1787 µg/g dry weight by Ca treatments for the 29 days of growth. No Ca deficiency symptoms were observed on the seedlings when the Ca concentration in the leaves exceeded 2300 µg/g dry weight. The Ca uptake rates during the 29 days of growth for ‘Lovell’ increased from 0.46 to 3.77 and for ‘Elberta’ from 0.44 to 2.84 µmoles/g fresh-weight-root/day. After 50 days of growth, Ca uptake rates increased for ‘Lovell’ from 0.58 to 3.51 and for ‘Elberta’ from 0.52 to 3.02 µmoles/g fresh-weight-root/day. Calcium accumulated in stems when Ca concentration in the nutrient solution exceeded 264 µm Ca with no change in total Ca content in the roots. The K and P uptake rates were increased by higher Ca treatments but the Mn uptake rate was decreased when the Ca concentration in nutrient solution was greater than 66 µm.
Pelargonium hortorum Bailey `Pinto Red' plants were grown with 220 mg·L−1 N (20N-4.4P-16.6K) using hand (HD), microtube (MT), ebb-and-flow (EF), and capillary mat (CM) irrigation systems. At harvest, root balls were sliced into three equal regions: top, middle, and bottom. A negative correlation existed between root medium electrical conductivity (EC) and N concentration to root number such that the best root growth was obtained with low medium EC and N concentrations. EF root numbers were greatest in the middle region. The two subirrigation systems (EF and CM) had higher average root numbers than the two surface-irrigation systems (HD and MT). For all irrigation systems, root numbers were lowest in the top region. In general, less difference in medium soluble salt and N concentrations existed between regions for surface-irrigated than for subirrigated root balls. Soluble salt concentration was lowest in the bottom and middle regions of EF and the bottom region of MT and CM. For subirrigation, the highest medium soluble salt and N concentration was in the top region. For all systems, pH was lowest in the bottom region. Plant growth for all irrigation systems was similar. EF and MT systems required the least water and EF resulted in the least runoff volume.
The primary component in greenhouse potting substrates is sphagnum peatmoss. Substrate solution pH of nonamended peatmoss ranges from 4.0 to 4.5 ( Landis, 1990 ). Optimum substrate pH has been determined for economically important crops such as
pH, and inconsistency between batches ( Hummel et al., 2014 ; Stoffella and Kahn, 2001 ). Since there are endless ingredients for making compost, the efficacy and rates for using each of these in greenhouse production are not well-understood ( Murray
will allow for efficient Sedum plant production to meet the increasing industry demand. Growing substrate pH influences plant growth and performance, and different plant species have optimal substrate pH ranges that are unique ( Reed, 1996
rates, target tissues, environmental conditions at application, and dosage ( Whipker et al., 2003 ). Spray solution water quality, particularly pH and alkalinity [presence of bicarbonates (HCO 3 − ) and carbonates (CO 3 −2 )], may also play a role in PGR
., 2012 ). Poinsettia grown in a Pythium -infested potting medium adjusted to pH 4.0–4.5 remained healthy compared with plants grown in an infested potting medium at pH levels >5.5 ( Bateman, 1962 ; Bolton, 1980 ). Substrate pH can also influence the
During the 1980s, many geranium producers observed a sporadic, unexplained decline in substrate pH. During the same time period, they also reported the occurrence of toxic concentrations of Fe or Mn in leaf tissue ( Bachman and Miller, 1995 ). In
the influence of root substrate and fertilizer on substrate pH. The addition of 20% sphagnum peat to fir bark resulted in a lower initial pH and more severe decline in substrate pH than fir bark alone ( Wang, 1998 ; Wang and Konow, 2002 ). Since the
Sudden pH decline (SPD) describes the situation where crops growing at an appropriate pH rapidly (within 1–2 weeks) cause the substrate pH to shift downward one to two units. Phosphorus (P) deficiency has been shown to cause plants to acidify