Irrigation scheduling based on penetrometer depth technique.
| dc.contributor.author | Moses, Chibuye Mambwe | |
| dc.date.accessioned | 2025-11-20T07:51:17Z | |
| dc.date.available | 2025-11-20T07:51:17Z | |
| dc.date.issued | 2001 | |
| dc.description | Dissertation | |
| dc.description.abstract | Efficient and profitable irrigation scheduling strategies are needed particularly in the arid and semi arid regions where available water resources are becoming more limited due to population growth and/or climate. Salinisation of ground water resources due to inappropriate water use is equally threatening large areas of productive irrigated land. To help sharpen the predictive capability of farmers with regard to soil water status, a study to model a simplified approach to irrigation scheduling based on soil resistance to penetration was undertaken at Sokoine University of Agriculture in Tanzania. Two locations representing two different soil types namely clay soil (SI) and sandy clay loam soil (S2) were used. Each location comprised of three blocks which were further subdivided into three plots. Three irrigation timing schedules were allocated to the plots in a Complete Randomised Block Design. Penetration depth at randomly selected spots was measured before and after irrigation for all the plots. The gravimetric determination of soil moisture content for each of the four penetrometer legs up to the penetration depth was done.Thereafter, two of the plants around the penetrometer were randomly selected, dug out and their tap length measured. The corresponding soil moisture content for the root length starting from average penetration depth to the entire extent of the root was then determined. The results showed that penetration depth is linearly related (r = 0.91 for SI and r = 0.82 for S2) to soil moisture content within the zone of penetration. Beyond average penetration depth, the soil moisture content for SI correlated poorly (r = 0.32) with average penetration depth while S2 correlated relatively high (r = 0.78). However, the multi variable model (i.e. root length and average penetration depth as variables) showed improved and highly positive correlation coefficients (r = 0.94 for SI and r = 0.96 for S2) with root zone moisture content beyond the penetration depth. Calibration of an individual soil type would make possible the relationship to be developed between penetration depth and depth of irrigation application otherwise the models would simulate soil moisture content.Model validation by using the t-test showed no significant difference (p < 0.05) between observed and simulated values for all the three models developed. The observed and simulated moisture contents of both models 2 and 3 in each of S1 and S2 were compared by using the t-test. The results showed no significant difference (p<0.05) although the mean simulated root zone moisture content of model 2 was closer to the mean observed root zone moisture content than the mean simulated value of model 3 for both locations. The results have shown that the penetrometer depth approach can be used to indicate soil moisture status and/depth of irrigation application in the upper soil of 0 - 30 cm which is used by farmers as an indicator of the soil water status and hence influences irrigation scheduling decisions. | |
| dc.description.sponsorship | Belgian Agency for Development Cooperation (BADC) | |
| dc.identifier.uri | https://www.suaire.sua.ac.tz/handle/20.500.14820/7148 | |
| dc.language.iso | en | |
| dc.publisher | Sokoine University of Agriculture | |
| dc.subject | Water resources | |
| dc.subject | Soil organic matter | |
| dc.subject | Soil Movement | |
| dc.subject | Geology | |
| dc.title | Irrigation scheduling based on penetrometer depth technique. | |
| dc.type | Thesis |