Reducing Egypt rock phosphate use in Zea mays cultivation on an acid soil using clinoptilolite zeolite

Insufficient supply of P for initial growth of crops does not only limit N uptake but it also leads to poor yield of crops. In acidic soils of the tropics, sorption of P occurs mainly on surfaces of Fe and Al oxides and hydroxides. Most of the P added through mineral fertilizers is fixed by high Al and Fe oxide concentrations and transformed into insoluble P compounds. Reduction of Al and Fe is important so as to ensure adequate supply and readily available P for crops uptake. A number of studies using zeolites as an amendment in the fertilization programs of crops have improved crops production, nutrients uptake, and nutrients use efficiency. However, there is dearth of information on the use of clinoptilolite zeolite (CZ) to reduce P fixation not to mention reduction of N, P, and K fertilizers use in agriculture. This study was conducted to: (i) determine dry matter production, nutrients concentration, nutrients uptake, and use efficiency of Zea mays (Hibrimas variety) by including CZ in the fertilization program of Zea mays planted on an acidic soil, and (ii) determine the effect of including CZ in the fertilization program of Zea mays on selected chemical properties of an acidic soil. Egypt rock phosphate (ERP), urea, and muriate of potash were used in this study. Seventy five percent (w/w) of the recommended N, P, and K fertilizers for Zea mays were combined with CZ. Standard procedures were used to determine soil pH, inorganic nitrogen, available phosphorus, exchangeable aluminium, iron, potassium, calcium, magnesium, and organic matter before and after planting. Zea mays were harvested at tasselling stage and measured for dry matter production, nutrients uptake and use efficiency. The effect of CZ application with 75% of fertilizers (E2) and 100% fertilizers (E1) were statistically similar for selected soil chemical properties, dry matter production, nutrients concentration, uptake of nutrients, and nutrients use efficiency except for N. Nitrogen use efficiency for E2 was better than that of E1. These findings suggest that adoption of CZ with 25% reduction of N, P, and K fertilizers are useful. Further field trials and economic analysis are recommended to confirm the findings of this study. These aspects are being investigated in our on-going field experiments.


Introduction
Phosphorus plays an important role in plant metabolism and it is one of the essential nutrients required for plant growth and development.Its deficiency in soils does not only limit N uptake but it also leads to poor yield of crops.In acidic soil of the tropics, dominance of metal hydroxides such as Al and Fe are responsible for P sorption.Application of P from the mineral phosphate results in P sorption through physical adsorption or chemical precipitation with dissolved Fe, Al, and Mn ions to form insoluble hydroxyl-phosphate precipitates (Sims & Pierzynski, 2005;Kochian et al., 2004;Brady et al., 2004;Fontes et al., 1996).Due to high P fixation and immobilization in acidic soils, high amount of P fertilizer is applied to saturate the capacity of acidic soils for P sorption and to ensure P availability for plant uptake.Excessive use of P fertilizers will become a greater threat as cumulative accumulation of available P in soils may enter water bodies through soil erosion (Zhou & Zhu, 2003)

Materia
The clinop (Bekenu s Sarawak C pass a 5.0 The soil u method (T using a di (Piccolo,  The pot study was conducted at Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia.The experimental design was completely randomized with four replicates.An 8 kg of soil was used per pot based on the soil's bulk density and pot size of 25 cm (top diameter) × 21 cm (bottom diameter) × 21 cm (height).Maize (Zea mays L.) Hibrimas (commonly used in Malaysia) was used as test crop.The recommended rates of N, P, and K fertilizers used were 60 kg N ha -1 , 60 kg P ha -1 , and 40 kg K ha -1 (Malaysian Agricultural Research and Development Institute, 1990).The recommended rates of the fertilizers used in this study were scaled down to per plant basis equivalent [Urea (4.85 g plant -1 ), Egyptian Rock Phosphate (ERP) (7.95 g plant -1 ) and Muriate of Potash (MOP) (2.47 g plant -1 )] from the standard fertilizer recommendation (Malaysian Agricultural Research and Development Institute, 1990).Treatments evaluated were as follows: (1) No fertilizer (T0) (2) 4.85 g urea + 2.47 g muriate of potash + 7.95 g Egypt rock phosphate (E1) (3) 3.64 g urea + 1.85 g muriate of potash + 5.96 g Egypt rock phosphate + 12.75 g zeolite (E2) The treatments consisted of without fertilizer (T0), application of 100% recommended fertilizers (E1), and 75% recommended fertilizers plus clinoptilolite zeolite (E2).The quantity of the CZ used in this study was derived from a ratio of [2.5:3] CZ to 100% fertilizers (w/w).
A day before planting, CZ was mixed thoroughly with soil before the mixture was filled in the pot.The volume of water for each pot was based on 60% of field capacity (Five seeds were sown and thinned to one at seven days after sowing).The muriate of potash (60% K 2 O), and Egypt rock phosphate (28% P 2 O 5 ), and urea (46% N) were surface applied and afterwhich they were covered with soil (to avoid for example loss of urea through ammonia volatilization).Unlike CZ which applied once in the beginning of the pot study, split applications of the fertilizers (amount of treatment applied as mention above divided by half at each time of application) were carried out on 10 th and 28 th days after seeding (DAS).Plants were harvested at 50 DAS (tasseling stage).
Tasselling stage is the maximum growth stage of the plants before they go to reproductive stage (Susilawati et al., 2009).
A day before harvesting, soil samples were taken using a mini auger.Afterwards, the soil was air dried, ground, and sieved to pass 2 mm and analyzed for physico-chemical properties using standard procedures as described previously.Plant leaves and stems were harvested at 50 days after seeding.The remaining roots in the soil were removed carefully and cleaned using tap and distilled water.The plant parts (leaves, stems, and roots) were then oven dried at 60ºC until constant weight was attained afterwhich their dry matter were determined.Each plant part was ground and analyzed for tolal N using Kjedahl method (Bremmer, 1965) whereas the single dry ashing method (Cottenie, 1980) was used for the extraction of P and K in the plant tissues.The filtrates were analyzed using atomic absorption spectrometry (Perkin Elmer AAnalyst 800) for K whereas P was determined using UV-spectrometer.Nitrogen, P, and K uptake in leaves, stems, and roots were determined by multiplying their concentrations with the dry weight of the plant parts, whereas N, P, and K use efficiency (agronomic effectiveness) were determined using the formula shown below (Dobermann, 2005): Nutrient Use Efficiency (%) = × 100 Where A = uptake with fertilizer, B = uptake without fertilizer, C = total amount of fertilizer that had been applied; uptake of nutrient = nutrient concentration (%) × dry weight (g).
Analysis of variance (ANOVA) was used to test significant effect of treatments whereas means of treatments were compared using Tukey test.Statistical Analysis System (SAS version 9.2) was used for the statistical analysis.

Dry Matter Production, Nutrients Concentration, Nutrients Uptake, and Use Efficiency
Plant dry matter production and nutrients concentration results are shown in Table 1.Application of CZ in the fertilization (E2) resulted in similar dry matter production as normal fertilization (E1).The poor dry matter production of plants in T0 was due to no fertilization to sustain plant growth and development.
Regardless of treatment, nutrient concentration in stem showed no significant effect.The treatment with CZ (E2) significantly increased N concentration in leaves compared with normal fertilization (E1) and no fertilization (T0).Unlike N, concentrations P in leaves and roots of the unfertilized plants were significantly higher than those of the fertilized plants.This is because plants with low dry matter normally show higher nutrient

Charac
The select shown in T value of C K, Ca, and    Paramananthan (2000).Nd = not determine.

Conclusion and Recommendation
The effect of CZ application with 75% fertilizers (E2) compared to 100% fertilizers (E1) were statistically similar for the selected soil chemical properties, dry matter production, nutrients concentration, nutrients uptake, and nutrients use efficiency except for N. Nitrogen use efficiency of E2 was better than that of E1.These findings suggest that adoption of CZ with 25% reduction of N, P, and K fertilizers are useful.Further field trials and economic analysis are recommended to confirm the findings of this study.These aspects are being investigated in our on-going field experiments.
Figure 2. 75% fert Figure fertiliz due to litter decomposition with time at the soil surface since the experimental soil was taken from an uncultivated area.

Table 3 .
Selected Chemical Properties of soil, clinoptilolite zeolite, and Egypt rock phosphate Subjected to the soil development, standard data range by