Nuclear techniques and DSSAT for optimizing Nitrogen Fertilizer Application under Irrigated Wheat

Transcription

1 Nuclear techniques and DSSAT for optimizing Nitrogen Fertilizer Application under Irrigated Wheat L.K. Heng, P. Moutonnet and W.A. Baethgen Introduction About 4% of the wheat produced in developing countries is irrigated. However, efficient use of water, nutrients and pesticides under irrigated conditions in these countries is low by international standards. It was reported that approximately 6% of the N fertilizer used in developing countries was lost. Recognizing the importance and implications, the Joint FAO/IAEA Division implemented a Co-ordinated Research Project (CRP) on The use of nuclear techniques for optimizing fertilizer application under irrigated wheat to increase the efficient use of nitrogen fertilizer and consequently reduce environmental pollution, to investigate fertilizer N uptake efficiency of wheat crops under irrigation through an interregional research network involving countries growing large areas of irrigated wheat. The aim was to use 15 N and the soil-moisture neutron probe to determine the fate of applied N, to follow water and nitrate movement in the soil, and to increase the nitrogen and wateruse efficiency in wheat cropping systems, consequently reduce environmental pollution. At the same time a database was constructed and the CERES-Wheat crop simulation model was used within the decision support system of DSSAT (Decision Support System of Agrotechnology Transfer) to formulate specific management strategies and fertilizer N-rate recommendation for the various production conditions. The project was carried out between 1994 and 1998 through the technical co-ordination of the Soil and Water Management and Crop Nutrition Section of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture ( Fourteen Member States of the IAEA and FAO participated: Austria, Bangladesh,, Chile,, Egypt, France,, Mexico,,, Syria, and United States of America. Table 1 gives a brief description of the participating institutions and the experimental design. The types, rates, methods of N fertilizer applied, and the timing of N application are also shown in Table 1. A full description of each experimental setup and the specific objectives of each participating institution can be found in the relevant document (IAEA, 2). In general, the rates of N chosen represent %, 5%, 1% and 15% of the regionally recommended application rate. 1

2 Table 1. Experimental setup of all participating countries Country Experimental site Wheat cultivars Fertilizer rates/type Application Method Bangladesh Experimental farm, Wheat Research Centre, Dinajpur cv. Kanchan, 6, 12, 18 kg N Topdress Chile Egypt Mexico-1 Mexico-2 Syria Research farm, Instituto Agronômico de Campinas, São Paulo State Irrigation Universidad de Concepción Agricultural Hebei Academy of Agricultural Sciences, Shijiazhuang city -Old irrigated clay soil Giza site -Newly reclaimed land (Ismailia & Nubaria sites) -Salt-affected El Serw soil n Agricultural Research Institute farm, New Delhi Experimental station at Yaqui Valley, Sonora Farmers fields in Yaqui Valley, Sonora Doukkala region Agricultural and Zootechnical Research Station, Oradea Wheat-growing area, 3 km SW of Aleppo City Research fields, Faculty of Agriculture, Çukurova University cv. IAC 24 cv. Coyan, Colono and Huayan cv cv. Sakha 69, Sids 6, Sids 1 cv. HD 2285, HD 2329 cv. Rayon F-89 cv. Altar C 84, Rayon F-89, 45, 9, 135, 18 kg N, 75, 15, 225 kg N, 75, 15, 225 kg N, Ammonium bicarbonate, 7, 14, 21 kg N as above + 28 kg N as Giza site Ammonium sulphate for all, 6, 12, 18 kg N, 84, 167, 25 kg N, ammonium sulphate, ammonium nitrate, 75, 15, 225, 3 kg N cv. Karim, 12, 18 kg N ammonium sulphate cv. Lovrin-41, 6, 12, 18 kg N Ammonium sulfate, urea cv. Sham 3 and Sham 6 cv. Seri 82, 5, 1, 15 kg N Ammonium sulfate, urea, 8, 16, 24 kg N Broadcast tillering. jointing (ZS-31). Incorporated to 1cm. - jointing (ZS-31). -three splits - jointing (ZS-31). 1/3 sowing, 1/3 knee high, 1/3 tasselling 1/3 sowing (, (NH 4 ) 2 SO 4 ), 2/ tillering ((NH 4 )NO 3 ) 1/3 planting, 2/3 six-week later. Broadcast vs banding. 1/3 at tillering, 2/3 at 1/3 at emergence, 2/3 at 1/3 at emergence, 2/3 Broadcast. 2

3 General Observations A large quantity of water was used to produce wheat. Losses of irrigation water and N-fertilizer were observed in many countries ( and Egypt on sandy soils, ). Well-scheduled sprinkler irrigation increased fertilizer-n recovery (Syria). The fertilizer recovery was relatively low. On the whole, the first one-third split application of N fertilizer (applied at planting) was usually recovered less efficiently than the second two-thirds split application (applied at the end of tillering); this observation was consistently made in seven countries during the period (Bangladesh,,,,, Syria and ). The relative amount applied in the second split may be increased as a result. Relationship between biomass and grain yield Grain Yield (kg/ha) Regression1 Regression Biomass (kg/ha) The relationship between dry matter production and grain yield for various countries DSSAT Simulations During the course of the experiments, a minimum dataset on soil, crop and climatic variables was collected for DSSAT CERES-Wheat simulation. Good agreement between observed and simulated results was obtained for most growth parameters in most of the simulations. Some of the preliminary simulations are given here. CERES-Wheat Grain Yield Simulated (kg/ha) :1 line Observed (kg/ha) 3

4 CERES-Wheat Total biomass Simulated (kg/ha) :1 line Observed (kg/ha) Individual country data were also simulated. For example, in the Doukkala region of, increasing nitrate concentrations in groundwater as a result of excessive fertilization and poor management of irrigation has been a cause for concern. It is hoped that with proper irrigation scheduling and split fertilizer application, it will be possible to reduce the amount of water loss and nitrate leached. Doukkala In Doukkala, most of the rainfall occurred at the beginning of the growing season, with about 8% falling during the first 6 days when the requirement for crop growth was minimal. This together with the sandy texture of the soil resulted in significant amounts of deep drainage. A large amount of N was also lost through leaching during the early part of the growing season. Fertilizer and irrigation timing is important. In this experiment, different rates of N fertilizer and different irrigation regimes were studied. DSSAT model was used to simulate the effect of irrigation as well as fertilizer rates on biomass production and leaching potential. Conclusion The ability to validate the model means that it can be used to refine specific management strategies with respect to fertilizer applications, yield and other parameters. 4

5 Reference Optimizing nitrogen fertilizer application to irrigated wheat. IAEA-TECDOC-1164, Vienna (2). 5