Use of Nuclear Techniques in Fertigation Studies at NRCAM

Transcription

1 Proceedings of The Fourth International Iran & Russia Conference 332 Use of Nuclear Techniques in Fertigation Studies at NRCAM Nosratollah Sagheb, Mehdi Naseri, A. Mousavi Shalmani, Mohammad Sadegh Hobbi, Hosein Abbasalian. Nuclear Research Center for Agriculture and Medicine Atomic Energy Organization of Iran Is. R., P.O. Box: 31485/498, Karaj- IRAN, Phone: , Fax: Abstract: Recognizing the potential use of nuclear techniques in fertigation studies, the Nuclear Research Center for Agriculture and Medicine (NRCAM) implemented a series of experiments. The main objective was to improve water and fertilizer management in field and green house using nuclear and fertigation technibgies. The techniques included the use of 15 N and 32 P isotopes and neutron moisture gauge for N, P and water management respectively. Non-isotopic fertilizers applied through drip irrigation system and labeled fertilizer applied for isotopic subplots through bottles. The amount of water and fertilizers applied through the bottles was equivalent to the concentration applied through a single dripper. In the studies such parameters like evaluation of 1) nitrogen and phosphorus amounts derived from soil and fertilizer 2) the fertilizer use efficiency 3) water use efficiency and 4) yield, were taken into consideration. For tomato fertigation the N- urea, P- phosphoric acid and water use efficiencies was found, 63, 23 and 16kg/m 2 respectively. As a whole, results are indicative of significant role played by combined nuclear and fertigation technologies in developing more efficient fertilizer and water management strategies for crop production in arid and semi- arid zone. Key words: crop yield, fertigation, fertilizer use efficiency, Isotope techniques, water use efficiency Introduction The only direct means of measuring nutrient uptake from the applied fertilizer is through the use of isotopes. Extensive work has been conducted using N- fertilizers labeled with the stable isotope 15 N and P- fertilizers labeled with the radioactive isotope 32 P. Initial work has been done with N and P utilizing isotopic methods, (Broeshart, 1978, Fried, 197, IAEA, 1970a, 1970b, 1971, 1974, 1975, 1978a, 1980, 1983a, FAO, 1980, Zapata and Hera, 1995). In isotopic- aided fertilizer experiments, a labeled fertilizer is added to the soil and the amount of fertilizer nutrient that a plant has taken up is determined. In this way, different fertilizer practices (Placement, timing, sources, etc.) can be studied. The first parameter to be determined when studying the fertilizer uptake by a crop by means of the isotope techniques is the fraction of the nutrient in the plant derived from the (labeled) fertilizer (IAEA, 2001). The nitrogen isotope composition, i.e. the 15 N/ total N ratio, of any material can be expressed as atom 15 N or simply 15 N abundance. This isotopic ratio of a sample is measured directly in a single determination by optical emission or mass spectrometry. Phosphorus has one stable isotope ( 31 P) and several radioisotopes but only two of them ( 32 P and 33 P) are suitable for agronomic studies. Detection efficiencies for both radioisotopes are high using modern liquid scintillation counters/ analyzers. The 32 P can

2 Proceedings of The Fourth International Iran & Russia Conference 333 be easily monitored because of its high beta energy and its use is limited to P uptake studies with duration of 60 up to 90 days due to its short half life (IAEA, 2001). Research on soil water and irrigation often depends on determination of actual soil moisture at many different experimental sites, at different depths in the soil and with different irrigation and other treatments. Soil water measurement based on neutron scattering has been a valuable tool for the past 50 years because it possesses many of qualities such as simplicity, reliability, repeatability, cost effectiveness, and the method is non-destructive (IAEA, 2001). Recognizing the potential use of nuclear techniques in soil water and plant nutrition studies, the NRCAM implemented a series of experiments. The main objective was to improve water and fertilizer management in field and green house, using nuclear and fertigation technologies. Chemigation is the application of any chemical through irrigation water. This may include insecticides, fumigants, nematicides, fertilizers, soil amendments, and other compounds. By far, the most common form of chemigation is fertigation, which refers to fertilizer application in the irrigation water. Fertigation as an attractive technology in modern agriculture increases yield, fertilizer and water use efficiencies (Burt et al., 1995). Materials and methods The 15 N and 32 p methodologies are used for evaluation of N and P nutrients derived from urea and phosphoric acid fertilizers by plant. Neutron moisture gauge used for soil water measurements and irrigation program. Recorded data 1- Dry matter yield (Dm) for plant parts. 2- Total N and P concentrations in dry matter. 3- Plant 15 N abundance and 32 P specific activity analyzed by emission spectrometry and LSC respectively. 4- Fertilizers 15 N abundance and 32 P specific activity. 5- The rates of N and P applications. Calculations for experiment with 15 N 1-15 N abundance = 15 N excess 15 atom N exces s in plant sample 2- Ndff = atom N exces s in fertilizer (m / ha) SDW(kg) 3- Dry matter yield (kg/ha) =FW(kg) 2 area harvested(m ) SFW(kg) Where FW is fresh weight per area harvested and SDW and SFW are sub sample dry and fresh weights, respectively. 4- N yield (kg/ha)= DM yield (kg/ha) N 100 Ndff 5- Fertilizer N yield (kg/ha)= N yield(kg/ha) 100 Fertilizer N yeild 6- Fertilizer N utilization = 100 Rate of N application

3 Proceedings of The Fourth International Iran & Russia Conference 334 Calculations for experiment with 32 P Spesific activity of plant sample Pdff = 100 Spesific acticivity of labelled fertilizer Dry mater yield, P yield, fertilizer P yield and fertilizer p utilization percent calculated as for 15 N equations. Calculations for soil water measurement Soil water storage in the plant rooting zone is calculated using water distribution profiles, which are assessed with neutron moisture gauge. The following equation is used to calculate the soil water storage. S(t)=Σφ Ζ Where S(t) is soil water storage, φ is the volumetric soil water content and Ζ is the depth of soil. The water balance approach was used to estimate crop water consumption. The difference between gain and losses of water over the depth L (plant rooting zone) gives rise to a net change of soil water storage (± s) which is measured with a neutron moisture gauge. The water balance equation is given as I+P-(D+ET)-R=± s Where, I is irrigation, P is rainfall, D is drainage, ET is evapotranspiration and R is run off. Following experiments were conducted at the Nuclear Research for Agriculture and Medicine in Rajaie- Shahr, Karaj about 60 km west of Tehran. Located at altitude of 1310 m, latitude 36N, longitude 51E, with average 250 mm annual rainfall and 13.6ºc air temperature. Experiment 1. In year 1998 urea fertilizer and water use efficiency by tomato (Early Urbana VF) in sandy loam soil were investigated comparing trickle fertigation and conventional furrow irrigation band fertilization. Following five treatments are replicated four times in a randomized complete block design. 1- Urea- N0= 0 mgnl -1 trickle fertigation 2- Urea- N1=38 mgnl -1 trickle fertigation 3- Urea- N2= 76 mgnl -1 trickle fertigation (equivalent NS treatment) 4- Urea- N3=114 mgnl -1 trickle fertigation 5- Urea- NS=500 kgnha. -1 conventional fertilization/ furrow irrigation On the trickle irrigated plots, fertilizers were applied through the irrigation system by the use of two fertigators: one for the application of urea and the other one for the application of diammonium phosphate and potassium sulfate. Installed micro tubes in the system splitted the urea. Six drippers in the middle row of each plot were blocked and the plants received 2 15 Na.e. urea through bottles. The amount of water and fertilizers applied through the bottles was equivalent to the concentrations applied through a single dripper. Access tubes for neutron probe reading in all treatments were installed in two replications at the depth of 100 cm below the drippers in the middle of second row. Readings with the neutron gauge were taken before and after each irrigation at 30, 45, 60, 75 and 90 cm soil depth. Water consumption (ET) was calculated on the basis of the ratio of fruit canopy dry matter weight to the unit of water consumed. As it is shown on Table1. the highest total dry matter yield was found 11.4 tons/ ha for the N2 treatment. Where as, the NS treatment produced the lowest (6.5 ton/ha) dry matter yield. Highest value for total nitrogen use efficiency percent (N.U.E

4 Proceedings of The Fourth International Iran & Russia Conference 335 ) in comparison belonged to N1 treatment with 54, which both parameters show statistical significance. The amount of irrigation water applied was 6450 and m 3 /ha for trickle irrigation and conventional furrow irrigation treatments respectively. As it is shown in table2. The highest water consumption was 99.4 cm for the NS treatment and the lowest water consumption was 52.9 cm for the N0 treatment. The water use efficiency was the highest for N1 treatment (94.4kg/ha.cm). It was the lowest for NS treatment (33.2 kg/ha.cm). Experiment 2. The effect of fertigation intervals on nitrogen, phosphorus and water use efficiencies on tomato (Early Urbana VF) evaluated using 15 N, 32 P and neutron gauge in at the N.R.C.A.M experimental field. The following five fertigation treatments were replicated four times in a randomized complete block design. T1: fertigation in every irrigation. T2: fertigation in every second irrigation. T3: fertigation in every third irrigation. T4: fertigation in every fourth irrigation. The amounts of fertilizer used were in accordance with the soil chemical analysis. The experimental field received 344 and 250 kgn/ha in 1999 and 2000 as urea, 97 kgp/ha as phosphoric acid and 266 kgk/ha as potassium sulfate through the irrigation system by use of one fertigator. Four drippers in the middle row of each plot were blocked and the plants received 2 15 N a.e urea through plastic containers. In order to study phosphorus fertilizer use efficiency, 15 plants were separated by the fence and three drippers in the middle of each fence were blocked and plants received 32 P labeled phosphorus through containers. Ortho phosphoric acid (4.5ml with activity of 17 mci) was made in the experimental reactor of Tehran. After dilution, the specific activity of the labeled fertilizer was MBq/gm. The total amount of labeled fertilizer divided into 36 units and applied with each irrigation. The amount of water, fertilizer, fungicide and micronutrients applied through a single dripper. Determination of the activity (dps) of the plant materials was done by radio assay technique using appropriate detector (Beta Counter). Access tubes (for neutron probe readings) were installed in duplicate to a depth of 100 cm below the drippers in the middle of the second row. Readings with neutron gauge were taken before and after each irrigation at 30, 60, 75 and 90 cm soil depth. Table 3 shows the results of the experiment. The highest N.U.E was found with T 1 treatment for 1999 and They were 42.0 and 62.8 respectively. The lowest N.U.E was found with the T4 treatment being 35.3 and 47.8 for 1999 and 2000 respectively. The highest total dry matter yield was observed for T1 treatment for 1999 and They were 10.9 and 11.5 ton/ ha (122 ton/ha fresh fruit yield) respectively. The lowest total dry matter yield was found with the T4 treatment being 8.7 and 8.8 ton/ha for 1999 and 2000 respectively. The results indicate that urea fertigation frequencies were not significant at 5 level related to dry matter, total nitrogen percentage and finally nitrogen use efficiency. This means that under general farm condition one can apply urea, phosphoric acid and potassium sulfate all together using one of the surveyed frequencies in this experiment. Table 4 shows the results of phosphorus isotopic analysis in different parts of tomato. The highest amounts of dry matter yield were recorded for fruits (5.81 Ton/ha). In this respect, phosphorus fertilizer uses efficiency were 11.7, 7.8, 2.2 and 1.6 for fruit, leaf, stem and root respectively percent of phosphorus fertilizer transferred to plant organs and 76.7 percent remained in the soil.

5 Proceedings of The Fourth International Iran & Russia Conference 336 Table 5 shows the fluctuation of phosphorus fertilizer use efficiency during six weeks of harvesting period. The highest amounts of dry matter yield and phosphorus yield were recorded during second and third weeks. Mutual effects of D.M.Y, total P and PdfF were affected in the phosphorus use efficiency and consequently 65 percent of P was absorbed by the fruit during these two weeks. The amount of irrigation water applied was 8215 and 7596m3/ha in respectively as it is shown in table 6 the highest fresh fruit yield were and ton/ha for T1 treatment in respectively, while the lowest fresh fruit yield were and ton/ha for T4 treatment in respectively. The highest water use efficiency was 14.2 and 16 kg/m3 for T1 treatment and the lowest (12.6 and 13.9 kg/m3) for T4 treatment in respectively. Conclusion Two out of a series of experiments have been presented in this paper specifically on their methodologies. Application of nuclear techniques in evaluation of water and fertilizer use efficiencies in this research improved precision in interpretation of nutrients, water and plant relationships. Fertigation technology is recognized as a desirable system for crop production in arid and semi arid regions and finally its potential use in our country requires more research. References 1- Broeshart H., (1974) Quantitative measurement of fertilizer uptake by crops. Netherlands Journal Agriculture Science 22, Burt C., O'Connor and Ruehr T., (1995) Fertigation. 3- FAO, (1980) Maximizing the efficiency of fertilizer use by grain crops. FAO Fertilizer and Plant Nutrition Bulletin No. 3. Rome. Italy. 4- Fardeau, J. C., Guiraud G., Marol C., (1996). The role of isotopic techniques on the evaluation of the agronomic effectiveness of P fertilizers, Fertilizer Research 45, Fried M., (1978) Direct quantitative assessment in the field of fertilizer management practices Trans. 11 th Int. Congress Soil Sci., Edmonton, P IAEA, (1971) Nitrogen 15 in soil plant studies. Panel Proceeding Series. STI/PUB/278. Vienna, Austria. 7- IAEA, (1974) Isotope studies on wheat fertilization. Technical Report Series No Vienna, Austria. 8- IAEA, (1975) Root activity patterns of some tree crops. Technical Report Series No Vienna, Austria. 9- IAEA, (1976) Tracer Manual on Crops and Soils. Technical Report Series No Vienna, Austria. 10- IAEA, (1978a) Isotope studies on rice fertilization. Technical Report Series No Vienna, Austria. 11- IAEA, (1980) Soil nitrogen as fertilizer or pollutant. Panel Proceedings Series. Vienna, Austria. 12- IAEA, (1970a) Rice fertilization. Technical Report Series No Vienna Austria. 13- IAEA, (2001) Training Course series 14. Use of isotopes and radiation methods in soil and water management and crop nutrition. 14- Zapata F, Hera C., (1995) Enhancing nutrient management through use of isotopic techniques. In: Proc Int. Symp. Nuclear and Related Techniques in Soil/ Plant Studies for Sustainable Agriculture and Environmental Preservation, October 1994, Vienna. IAEA bsti/pub/947, Vienna, Austria. pp

6 Proceedings of The Fourth International Iran & Russia Conference 337 Tables Table1. Total dry matter and urea N utilization of tomato Treatment D.M.Y T.ha -1 Total N N. yield Kg ha -1 Ndff F.N.Y Kg ha -1 N.U.E Fruit N0 3.0 B N1 5.1 A A N2 5.2 A B N3 4.6A B B NS 3.3 B C Canopy N0 4.3 AB N1 5.2 AB A N2 6.2 A A N3 4.7 AB A NS 3.2 B B 22 7 B Total N0 7.3 AB N A A N A B N3 9.3 B B NS 6.5 AB C - Values in columns followed by the same letter are not significantly different at the 5 probability level. Table 2. Effect of irrigation method and N rates on fruit dry matter yield, evopotranspiration (ET) and water use efficiency (WUE) according to neutron probe calculation for tomato in Treatment Dry matter (ton/ha) ET(cm) WUE(kg/ha.cm) N N N N NS Table 3: Dry matter yield, total N, NdfF, fertilizer N yield and N use efficiency of tomato (Total) as affected by different intervals urea application during ( ). Trea. D.M.Y ton/ha Total N NdfF F.N.Y kg/ha N.U.E T T T T CV

7 Proceedings of The Fourth International Iran & Russia Conference 338 Table4. Dry mater yield, Total phosphorus, P yield, Phosphorus derived from fertilizer (PdfF), Fertilizer Phosphorus yield (F.P.Y), Phosphorus fertilizer use efficiency (P.U.E), in different parts of tomato Plant parts Leaf Root Stem Fruit CV. D.M.Y Ton/ha 3.3 B 0.87 C 1.83 C 5.81 A 21 Total P 0.57 A 0.40 B 0.28 C 0.54 A 9 P yield B 3.52 C 5.04 C A 24 PdfF 39.8 ns 44.1 ns 42.2 ns 35.9 ns 32 F.P.Y Data : mean of four replications - The same letter in a column, refers to no significant difference in 1 level (Duncan's test) - P.U.E 7.76 A 1.60 B 2.20 B A 33 Table 5. The comparison of fertilizer phosphorus use efficiency during six harvesting times of tomato fruit2000. Harvesting time D.M.Y P yield F.P.Y (Days after Ton/ha cultivation) CV 0.58 C 2.16 A 1.58 B 0.52 C 0.71 C 0.26 C 24 Total P 0.52 B 0.43 B 0.57 B 0.47 B 0.80 A 0.81 A B 9.31 A 9.03 A 2.44 B 5.69 AB 2.12 B 33 PdfF AB A AB A B B Data : mean of four replications - The same letter in a column, refers to no significant difference in 1 level (Duncan's test) - P.U.E 1.04 B 4.41 A 3.23 A 1.14 B 1.29 B 0.57 B 29 Table6: Effect of different fertilization intervals on fresh fruit and water use efficiency (WUE) for tomato Treatment Fresh 1999 Fruit (ton/ha) Water use Efficiency (Kg/m 3 ) 2000 T A T A T A T A Values in columns followed by the same letter are not significantly different at the 5probability level.