کم آبیاری

Nowadays, the management of water resources has become one of the major challenges in the world due to recent droughts and water shortages. Therefore, timely and non-destructive monitoring of Water use efficiency (WUE) and yield of plants to screen cultivars with high water use performance and efficiency and rational allocation of water has become one of the important goals in agriculture. Compared with traditional crop Yield and WUE monitoring and diagnostic tools, hyperspectral remote sensing technology has made it possible to obtain water use efficiency and Yield by taking advantage of large amounts of continuous data on a large scale. Therefore, this study aimed to create a model capable of estimating the WUE and Yield of tomato plants based on hyperspectral remote sensing data by establishing a relationship between common spectral indices and WUE and Yield in greenhouse conditions.

The research was carried out during the growing season of 2021 from January to June at the research greenhouse of the Department of Water and Environmental Engineering, Shahid Chamran University, Ahvaz, Khuzestan Province, The main factor was irrigation treatments in three levels including full irrigation, 20%, and 40% deficit irrigation, and the sub-main factor was silica nanoparticles with concentrations of 0 and 100 mg/lit. The pot experiment plot was laid out in a split plot in a randomized complete design (RCD) with four replications (120 pots in total). Then Tomato yield and WUE under the various treatments, were calculated. Canopy hyperspectral reflectance was measured using a portable spectrometer (ASD FieldSpec 3) operated in the spectral range of 350-2500 nm. The spectral data acquisition was conducted in four stages of plant growth during the growing season and the data were used to calculate spectral indices NWI5, WI3, WI4, NDVI, NDVI, and OSAVI. Then the ability of spectral indices to evaluate the water use efficiency and yield of tomato plants in different irrigation regimes and nanoparticles was investigated. Analysis of variance (ANOVA) was performed on spectral indices and WUE and yield of tomato plants using a split plot design. The PROC GLM method of SAS software (version 9.4, SAS Institute, Inc., Cary, NC, USA) was used for this analysis. Then, in order to compare the averages and whether they have a significant difference with each other at the 0.01 and 0.05 levels, the least significant difference (LSD) test was used.

The results showed that the Water use efficiency (WUE) under deficit irrigation treatments is increased with increasing water stress but the yield of tomato decreases with increase of water stress. In addition, the WUE and yield of tomato increases with increasing the concentration of silica nanoparticles (from 0 to 100 mg/liter). The value of NDVI and OSAVI indices decreased with the increase of water stress, while the value of RDVI, WI3, WI4 and NWI5 indices increased. The amount of NDVI and OSAVI spectral indices in the treatment containing 100 mg/liter nanoparticles was higher than the treatment without nanoparticles. Also, the amount of spectral indices RDVI, WI3, WI4 and NWI5 in nanoparticles with a concentration of 100 mg/liter was lower than the control treatment (zero concentration). The results also showed that the coefficient of determination between the different spectral indices and the WUE and Yield index was 0.55**Furthermore, among the six spectral indices, three spectral indices (NWI5, WI3, and WI4) jointly met most of the criteria used to determine the accuracy of the models for predicting yield and WUE

Maintaining existing water resources through improving irrigation management and increasing water use efficiency and Yield of plants is the main goal for the sustainable development of water agriculture. As a result, rapid and non-destructive monitoring of water use efficiency and Yield is of great importance in improving irrigation management of crops and saving water consumption. significant relationship with yield and WUE index of tomato plants in greenhouse conditions. In conclusion, Spectral indices studied in this research could be useful and non-destructive assessments of the water use efficiency and yield of tomato in greenhouse conditions.

Introduction:

 The highest amount of water consumption is allocated to the agricultural sector, which has led to a water crisis due to increasing demand for food production and non-conservative agriculture and climate change in some countries. Sugarcane needs a lot of water during the growing season and is sensitive to drought. In drought conditions and water stress, the intensity of reverse flow of water to the soil surface increases and can cause salinization of the soil around the roots of sugarcane, which is a relatively sensitive plant related to salinity. Due to the high-water consumption in sugarcane fields and also the shortage and decline of water quality in dry years, this study aimed to investigate the effect of conventional and deficit irrigation by variable and fixed alternate furrow irrigation on soil salinity and some nutrient concentration consist of phosphorous and potassium in sugarcane field.

Materials and Methods:

 To investigate the effect of irrigation methods on salinity distribution and concentration of phosphorous and potassium in soil, this experiment was conducted with independent variables of irrigation method treatment including conventional (complete) irrigation, variable alternate furrow irrigation and fixed alternate furrow irrigation, irrigation round treatment including before irrigation, after one and two times irrigation, sampling location treatment including bottom, middle and top of raised bed and sampling position treatment consist of start, middle and end of furrow. The experiment was performed factorially in a completely randomized design with three replications in sugarcane fields of MianAb in Susa. Statistical analysis was performed using SPSS software and mean comparisons were performed by Duncan's multiple range test. Charts were drawn using Excel software.

Results and Discussion:

 The results showed that irrigation method is mainly affects salinity distribution and concentration of phosphorus in soil. The fixed alternate furrow irrigation method had the greatest effect on soil salinity changes and reduced the salinity as compared to the conventional method and the variable alternate furrow irrigation. In general, in the conventional irrigation method (complete irrigation of all furrows) and variable alternate furrow irrigation, there is no constantly dry furrow as compared to the fixed alternate furrow irrigation method, and this intensifies the accumulation of salts on the sides and the top of raise beds. Increasing the frequency of irrigation (irrigation round) reduces the soil salinity so that in soil samples before irrigation, soil salinity was 2.30 dS/m and with one round irrigation, this amount decreased by 7.8% to 2.12 dS/m and with two rounds of irrigation reached to 2.09 dS/m. In terms of locative variation of salinity related to the fixed alternate furrow irrigation method, the lowest amount of salinity was observed in the bottom of the raised bed. With increasing distance from the beginning of furrow, an upward trend in soil salinity was reported. Regarding the change in the amount of available phosphorus in the soil under the influence of irrigation method, any of the deficit irrigation methods can be used as an alternative to conventional irrigation. The highest amount of soil phosphorus was reported in the middle of the raise bed. Soil potassium changes were not directly affected by irrigation method and the highest amount was assessed in the bottom of the raise bed. In terms of salinity, the lowest value was at the bottom of the furrows and the highest value was at the top of the raise bed. Unlike salinity changes, soil phosphorus had the highest accumulation in the middle of the raise bed and reached a minimum at the top of the raise bed. A relatively uniform trend was observed in changes in soil phosphorus from the beginning to the end of the furrow. Contrary to salinity changes, the highest amount of available potassium in soil was observed in the bottom of raise bed and a decreasing trend in soil potassium was reported from the beginning to the end of furrow. In general, based on the results, the average level of soil salinity and potassium and the highest amount of phosphorus were reported in the middle of the raise bed.

For optimal water use and soil salinity management, application of deficit irrigation methods especially fixed alternate furrow irrigation instead of conventional irrigation method, is recommended. In case of salinity and concentration of mentioned nutrients, the top of the raise bed in all three irrigation methods, would not be a suitable place for plant cultivation.