Edgar L. Vinson

Plastic Mulches and Row Covers on Growth and Production of Summer Squash

ABSTRACT Row covers and colored plastic mulch are used routinely throughout the United States to grow vegetables but are rarely used in conjunction to produce a crop. Summer squash (Cucurbita pepo L.), cv. Prelude II, was grown on an Orangeburg sandy loam soil in Shorter, AL. The summer squash was direct seeded in single rows. The experiment consisted of 12 treatments including: (1) black plastic mulch (BPM)+spunbonded row cover (RC), (2) BPM alone, (3) white plastic mulch (WPM)+RC, (4) WPM alone, (5) red plastic mulch (RPM)+RC, (6) RPM alone, (7) bare soil (BS)+RC, (8) BS alone, (9) silver plastic mulch (SPM)+RC, (10) SPM alone, (11) blue plastic mulch (BLUPM)+RC, and (12) BLUPM alone. Year and mulch color affected all variables, row cover affected plant height and stem diameter, and the mulch color × row cover interaction affected yield variables. Mulch color and year significantly affected air and soil temperatures and row cover significantly affected air temperature. Soil temperatures were more than 5°C lower than air temperatures in all treatments and air temperatures were 2–5°C higher with row covers than without. Increased soil and air temperatures did not always result in yield increases. Colored plastic mulch with or without row covers did not increase early fruit yield in squash. Lack of a mulch/row cover induced temperature effect on yield was attributed to the relatively high mean air temperatures that may have masked treatment temperature effects.

COMPARISON OF THREE CONTROLLED-RELEASE NITROGEN FERTILIZERS IN GREENHOUSE CROP PRODUCTION

Controlled-release nitrogen fertilizers allow growers to reduce nitrogen loss from leaching in comparison to soluble formulations. Plant growth and nitrogen leaching during greenhouse production of Begonia   ×   semperflorens-cultorum Hort. cv. “Brandy” (Begonia), Euphorbia pulcherrima Willd. ex Klotzch cv. “Freedom Red” (Poinsettia), Ficus benjamina L., and Nephrolepis exaltata (L.) Schott cv. “Bostoniensis” (Boston Fern) were evaluated for eight weeks using three commercial controlled-release nitrogen fertilizers in combination with phosphorus and potassium sources to maintain a 3 : 2:1 NPK ratio. Mini Polymer Coated Urea (MPCU) 41-0-0, Trikote 42-0-0, and Regalite Nitroform (RN) 38-0-0 were incorporated into the substrate at rates of 0.9 kg nitrogen (N) m−3 and 1.5 kg N m−3 prior to potting. Total soluble salts in the leachates reflected the initial leaching of salts from the substrate, some increase or maintenance of salt levels through the third week, and lower levels from the fourth through eighth weeks. The high and low rates of Trikote and the high rate of MPCU provided acceptable levels of NH4 + for production purposes through the fourth or fifth week, the low rate of MPCU provided low levels through the third week and minimal levels thereafter, while both levels of RN showed progressive decreases from the outset. NO3 − levels varied within treatments during the eight-week period, with levels suitable for production observed during the trial with MPCU and Trikote, and declining to low levels with RN. Growth indices were similar among treatments, with the exceptions of Begonia and Poinsettia, which were larger with a low rate of RN 40 days after potting (DAP). Begonia was also larger with a low rate of Trikote 40 DAP. Shoot fresh weights (SFW) of Begonia and Poinsettia were higher with a low rate of Trikote than with MPCU or RN 40 DAP, and higher for Poinsettia with low rates of both MPCU and Trikote compared to RN 57 DAP. SFW and shoot dry weights (SDW) were similar among treatments with Boston Fern and Ficus benjamina.

EFFECT OF CURRENT FERTILIZATION PRACTICES ON NUTRITIONAL STATUS OF DOUBLE-CROPPED TOMATO AND CUCUMBER PRODUCED WITH PLASTICULTURE

When vegetables are double-cropped on polyethylene mulch, fertilizer recommendations for each crop may need to be adjusted because liming and preplant applications are done prior to laying plastic. When current fertilizer recommendations for single crops were used for cucumber following tomato, the cucumber plants looked like green, indicating a nitrogen (N) and/or potassium (K) deficiency was developing, suggesting that nutrient availability for the second crop was not adequate for producing the highest yields. Therefore, the nutritional status of both crops was diagnosed using sufficiency range data and DRIS norms to determine which nutrient(s) was limiting crop nutrition. Regardless of N source used as a sidedress injection material (at a rate of 7 kg N ha−1wk−1 as ammonium nitrate or calcium nitrate) or liming material used to adjust soil pH to 6.5 (carbonate- or oxide-based calcitic or dolomitic lime), foliar levels of N and K, and possibly phosphorus (P) were found to be limiting factors according to sufficiency range data and DRIS norms. This study suggests that current fertility recommendations for tomato and cucumber grown as single crops in Alabama need to be reevaluated for double crops.

EFFECT OF LIMING MATERIALS ON SOIL AVAILABLE NUTRIENTS, YIELD, AND GRADE DISTRIBUTION OF DOUBLE-CROPPED TOMATO AND CUCUMBER GROWN WITH PLASTICULTURE

For economical reasons, cucumber (Cucumis sativus L.) may be grown as a double crop after tomato (Lycopersicon esculentum Mill.). In this production system, plant nutrition may be limited for the second crop due to pH change or insufficient levels of calcium or magnesium. The objective of this 2-year field study was to compare the effects of selected liming materials on yield and grade distribution, and soil available nutrients of a tomato/cucumber double crop produced with plasticulture. Liming materials were compared to a control and a CaSO4 treatment based on the same neutralizing value as standard agricultural limestone. Supplemental N fertilization was provided by weekly injections at a rate of 7 kg/ha/week from ammonium nitrate (NH4NO3) or calcium nitrate [Ca(NO3)2]. Each year, soil samples were collected at the beginning of the study and after each crop to determine nutrient availability. All liming materials raised soil pH in 1998 and 1999 over the unlimed control, though not to the target level for tomato and cucumber production (pH 6.5). Throughout the study, agricultural limestone, a high CaO-containing blend (calcitic blend) and a CaO/MgO (dolomitic blend), resulted in greater fruit weights compared to the control and CaSO4. These materials, along with quick lime (CaO), provided higher levels of soil Ca and Mg available for plant growth. However, it was found that current recommendations for potassium (K), regardless of liming source, were not adequate for optimal soil reserves and yields in this tomato/cucumber cropping system. Ammonium nitrate as a source of N for fertilization was as effective as Ca(NO3)2.

Nitrogen Release Rate Differs by Fertilizer Source

Abstract Controlled-release fertilizers allow growers to reduce leachate nitrogen loss and better manage crop nutrition in comparison to water-soluble fertilizers. Nitrogen leaching and plant growth were evaluated in a container production system using a granular water-soluble (GWS) ammonium nitrate fertilizer (34-0-0), a controlled-release fertilizer (CRF) (18N-6P-12K), and a non-fertilized control (NFC). Selected plant species were grown for ten weeks using 1,485 g N per cubic meter (2.5 pounds N per cubic yard) CRF or the GWS fertilizer. Leachate pH was higher (7.0+) for the GWS and NFC treatments than the CRF (6.5 to 7.0). Total soluble salts in the leachates reflected the initial leaching of salts from the substrate, with a continued decrease in soluble salts for the GWS fertilizer and NFC treatments. With the CRF, soluble salts decreased slightly during the first five weeks, but then increased over the next five weeks. The CRF provided acceptable ammonium levels for production purposes throughout the ten-week period, while the GWS fertilizer and NFC treatments both showed progressive decreases in ammonium levels throughout the ten-week period, becoming inadequate for production. Nitrate levels varied during the ten-week period, with levels declining to insufficient amounts with the GWS fertilizer and NFC treatments, while the levels for the CRF were suitable for production throughout the study. Growth indices, fresh matter weights, and dry matter weights were higher with the CRF than with both the GWS fertilizer and NFC treatments.