1. The Impact of Nanophase Iron-Oxide Coated Clinoptilotite Zeolite On Nutrient Retention in A Sand-Based Root Zone Mix Peter Ampim 1, John Sloan 1, Rajan K. Vempati 2 and Yingzhe Wu 1 1 Soil and Crop Sciences, Texas AgriLife Research, Dallas, TX; 2 ChK Group Inc., Plano, TX INTRODUCTION Sand-based growing media generally lack the capacity to retain nutrients in the root zone because they have low cation exchange capacities (CEC). Adding organic matter to improve CEC of these media may lead to nitrification of ammonium fertilizers and leaching (Brown et al., 1977). However, natural clinoptilotite zeolites coated with with nanophase iron-oxide (NPNZ) adsorb both cations and anions. Thus mixing them into a sand based growing medium may enhance nutrient retention and reduce leaching losses. Additionally, the iron coated zeolites can be pre-charged with fertilizer nutrients prior to blending it with greens-grade sand in order to reduce future fertilization requirements. 43-5 MATERIALS AND METHODS 1.Nanophase iron oxide-coated natural zeolites (NPNZ) were charged with soluble fertilizer (15-30-15 plus micronutrients) and air dried (Fig. 1A). 2.Fertilized NPNZ was blended with USGA greens grade sand (Fig. 1B) at rates of 0, 5, 10, and 20% (w/w) to create the experimental root zone mixes (RZM) (Fig. 1C). 3.RZMs were placed in 25.4 cm dia. X 35.6 cm greenhouse lysimeters and planted with 49 kg/ha Crenshaw bentgrass seeds (Fig. 1C). 4.Equal volumes of water were added to each lysimeter as needed. All leachate water was collected for nutrient analysis (Table 1). 5.Since the initial amount of fertilizer present in each treatment depended on the amount of NPNZ in the RZM, five additional fertilizer applications were made throughout the study to make up for the deficit (Table 1). 6.Grass clippings were collect 4 to 5 weeks after each fertilizer application, dried at 60ºC and weighed, and then ground to <1mm and analyzed for total N and P (Table 2). Fig. 2. Experimental set-up in the green house. Crenshaw bentgrass (planted at 49 kg/ha) Leachate Lysimeter (Lys) Table 2. Chemical Analyses ~ pH and EC of leachate samples Used Acumet AR 50 (Fisher Scientific) ~ Nutrients in Leachate Used colorimetric methods with spectrophotometer (Shimadzu) P - Olsen et al. (1982) NH 4 -N - Mulvaney (1996) NO 3 -N – Cadmium Reduction Urea-N - Douglas and Bremmer (1970) ~ Nutrients in Grass Tissue Tissue C & N determined by CNS analyzer (Elementar) Tissue P analyzed by dry ashing followed by Olsen et al. (1982) method Acumet AR 50 Spectrophotometer CNS Analyzer Fig. 1. Root Zone Mix (RZM) Constituents: A) nanophase iron oxide-coated natural zeolite (NPNZ); B) USGA greens grade quartz sand; C) blended NPNZ plus sand. Fe-oxide coated Zeolite (A) USGA Sand (B) Fertilized NPNZ (C) CONCLUSIONS Nanophase iron oxide-coated natural zeolites (NPNZ) increase the retention of fertilizer nutrients (P > N) in sand-based root zone mixes (RZM). Increased nutrient retention in the RZM comes at the cost of reduced plant availability. The amount of fertilizer added to NPNZ prior to blending with greens grade sand should not exceed its nutrient absorbing capacity in order to prevent excessive leaching of nutrients. Urea-based fertilizer should be avoided in sand-based RZM that contain NPNZ. A 5 to 10% addition of NPNZ to a sand-based RZM is sufficient to protect nutrients from leaching without excessively decreasing plant availability of those nutrients. Table 1. RZM treatments with initial nutrients levels, additional nutrient applications, and total amounts applied. OBJECTIVE Investigate the influence of nanophase iron-coated natural zeolite (NPNZ) on the growth of Crenshaw Bentgrass and leaching of fertilizer nutrients in a sand-based growing medium. Fig. 3. Electrical conductivity levels in leachate from 0, 5, 10, and 20% NPNZ treatments after the (A) first, (B) second, (C) third, and (D) fourth+fifth fertilizer applications. Fig. 4. Leachate pH from 0, 5, 10, and 20% NPNZ treatments after the (A) first, (B) second, (C) third, and (D) fourth+fifth fertilizer applications. ACDB A C D B RESULTS AND DISCUSSION Most of the initial fertilizer leached quickly from the RZM (Fig. 3A). Subsequent fertilizer applications leached easily from the sand (Fig. 3B-D), but the amount leached was also proportional to the amount of fertilizer added (Table 1). Increases in pH following addition of urea-based 15-30-15 fertilizer suggested that the presence of NPNZ in the RZM enhanced urea hydrolysis and production of the intermediate (NH4) 2 CO3 (Fig. 4A). As acidity was generated by nitrification, pH was decreased in the unbuffered sand RZM compared to the NPNZ treatments (Fig. 4B-D). NPNZ greatly reduced the amount of fertilizer N and P leached from the lysimeters during the course of the study (Fig. 5A-B), especially when using split fertilizer applications. Bentgrass clipping weights demonstrated that fertilizer nutrients added to a RZM containing NPNZ are less available for plant uptake compared to those added to a pure sand RZM (Fig. 6A-C). Fig. 6. Effect of 0, 5, 10, and 20% NPNZ additions to USGA greens sand on (A) bentgrass clipping weights, (B) bentgrass tissue N content, and (C) bentgrass tissue P content for the first four harvests. ACB Fig. 5. Total amount of fertilizer N and P leached from sand based RZM containing 0, 5, 10, or 20% NPNZ.