H J; P A; M D; M T
Abstract
Evapotranspiration of orchard crops is often determined by indirect method and based on meteorological data due to the difficulties inherent in direct measurement instruments such as installation of large lysimeters or precision equipment, and long growing seasons of tree crops. Evapotranspiration estimation ...
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Evapotranspiration of orchard crops is often determined by indirect method and based on meteorological data due to the difficulties inherent in direct measurement instruments such as installation of large lysimeters or precision equipment, and long growing seasons of tree crops. Evapotranspiration estimation with sufficient accuracy is not feasible due to spatial variability of meteorological parameters and, sometimes, due to inappropriate distribution of meteorological stations. Therefore, using methods based on remote sensing, which account for these variations, is much more desirable. In this research, evapotranspiration of olive trees at different phonologic stages was measured using direct and indirect methods in Tarom district of Zanjan Province. In the direct method, actual evapotranspiration was determined by measuring moisture balance components, whilst in the indirect one, it was specified with the help of satellite imagery, the SEBAL algorithms, and Penman-Monteith equation. Olive crop coefficient was subsequently calculated and evaluated by determining reference crop evapotranspiration. The results indicated that evapotranspiration calculated by the remote sensing method at different stages of the growth had acceptable conformity with soil moisture balance data and evapotranspiration values obtained from the Penman–Monteith equation (the respective correlation coefficients were 0.95 and 0.88) and both evapotranspiration curves along the growing season had a similar increasing and decreasing trend. Moreover, crop coefficient obtained by the SEBAL algorithm and the water balance methods were well correlated (R2=0.86) and the remote sensing method with the aforementioned advantages can be used in predicting evapotranspiration.
n k; a a; k d
Abstract
Plant yield is a function of root distribution and its activity. Under limited water conditions, adequate root growth and efficiency are essential for crop productivity. To study the relationship between the dynamics of corn (Zea Maize L., variety single cross 704) root growth and soil available water ...
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Plant yield is a function of root distribution and its activity. Under limited water conditions, adequate root growth and efficiency are essential for crop productivity. To study the relationship between the dynamics of corn (Zea Maize L., variety single cross 704) root growth and soil available water uptake under drip-tape irrigation system, an experiment was conducted in a randomized complete block design with three replications. Experimental variables were three irrigation treatments including: 100% (I1), 80% (I2), and 60% (I3) of the actual plant water requirement calculated by the Penman–Monteith formula using meteorological data. The roots were collected from the beginning to the end of the growing season at four stages including: 25, 55, 85 and 115 days after planting. Samples were taken from 5 depths: 0-10, 10-20, 20-30, 30-40, and 40-50 cm. The results showed that irrigation treatments had significant effect (p=0.01) on root length density at different depths. About 60% of the corn root length density was up to the depth of 20 cm. On the other hand, the surface layers of the soil at this depth lost their moisture rapidly and, therefore, the plant needed to absorb water from the lower layers (below 20 cm) to survive. In low irrigation treatment (60% water requirement) up to the depth of 40 cm, root growth was low and, as a result, water absorption was also low. Higher irrigation had a positive effect on corn yield as the highest yield (7769 kg/ha) was obtained with the irrigation treatment of 100% water requirement.