Impacts of fertigation via sprinkler irrigation on nitrate leaching and corn yield in an acid-sulphate soil in Thailand | |
| Author | Asadi, Mohammad Esmaeil |
| Call Number | AIT Diss. no. WM-00-02 |
| Subject(s) | Plants, Effect of nitrates on Acid sulphate soils--Thailand Corn--Yields--Thailand |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Engineering Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WM-00-02 |
| Abstract | A study was conducted in an acid sulphate soil in the central region of Thailand, in 1999 and 2000 to assess the influence of different rates of N fertigation on corn (Zea mays L.) yield and nitrate leaching. Nitrofen source was urea and there were four N fertigation treatments which include 0 kg N ha- (control), 100 kg N ha-1, 150 kg N ha-1, and 200 kg N ha·1, each having three replications arranged in a randomized complete block design (RCBD). Soil was irrigated to field capacity at 50% available soil moisture depletion regime throughout the season. Leaching losses were calculated from measured daily fluxes of water percolation, while soil water N03-N concentrations were extracted by soil water sampler and obtained from a seasonal N mass balance. The average maximum corn grain yield of 3.52 t ha·1 was obtained at 200 kg N ha·1 in 1999 and 5.42 t ha·1 was obtained at 150 kg N ha·1 in 2000. But the statistical analysis did not show any significant differences in grain yield between N200 and N150 treatments in either year. The lowest yield of 0.55 and 0.98 t ha·1 were obtained at 0 kg N ha-1 in 1999 and 2000 respectively. The leaching measurements showed that the highest values were obtained in N200 treatments in both years with 23 and 5.3 kg N ha-1 in 1999 and 2000, respectively. Throughout 1999, an especially rainy year, the experimental data clearly showed that N03-N leached beyond typical maize rooting depths (30 cm). Using nitrogen balances as a tool for estimating nitrate leaching suggests that this approach can not be used as a direct measure for nitrate leaching in a specific area. Also the results showed that a fertigation system can be an efficient practice and an advanced way to give water and plant nutrients together to the crop. The CERES-Maize of DSSAT (V.3.5) computer software was used to simulate N03-N leaching, N uptake, and corn yield, and predicted values were compared with observed data. Statistical methodologies to calculate the correlation coefficient (r), average error (AE), relative error (RE), the standard error of estimate (SE), and the coefficient of variation (CV) between the observed and simulated data were also used to evaluate the performance of model. The validation results showed that the discrepancies between observed and simulated values are generally small in both years. The model overpredicted corn grain yield slightly for some treatments, underpredicted total biomass slightly for all treatments, generally overpredicted total N uptake and underpredicted total N leached. The lower observed maize grain yields at high rates of nitrogen application was due to experimental factors which the model is not sensitive. Despite this, the statistical parameters indicate that the model performed well. The relation between results obtained from experiment (Yo) and simulation (Ys) was expressed by the equation Ys= l.058Yo with r2=0.97 for grain yield, Ys=0.7396Yo with r2=0.86 for nitrate leaching, and Y s= I. l 103Yo with r2=0.99 for total N uptake. Validation results showed the reliability and good performance of the model. The study also showed that the CERES-Maize of DSSAT model may be applied with confidence to study effects of N and irrigation management on maize yield, nitrate leaching and N uptake under irrigated tropical conditions. |
| Year | 2001 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-00-02 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Clemente, Roberto S.; |
| Examination Committee(s) | Gupta, Ashim Das ;Singh, Gajendra ;Loof, Rainer ;Izumi, . Norihiro ;Jong, Reinder De ; |
| Scholarship Donor(s) | Agricultural Research, Education and Extension Organization (AREEO), Iran; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology,2001 |