10 research outputs found
Effects of different on-farm management on yield and water use efficiency of Potato crop cultivated in semiarid environments under subsurface drip irrigation
In Tunisia the amount of water for irrigated agriculture is higher than about 80% of the total resource.The increasing
population and the rising food demand, associated to the negative effects of climate change,make it crucial
to adopt strategies aiming to improve water use efficiency (WUE). Moreover, the absence of an effective public
policy for water management amplifies the imbalance between water supply and its demand. Despite improved
irrigation technologies can enhance the efficiency of water distribution systems, to achieve environmental goals it
is also necessaryto identify on-farm management strategies accounting for actual crop water requirement.
The main objective of the paper was to assess the effects of different on-farm managementstrategies (irrigation
scheduling and planting date) on yield and water use efficiency of Potato crop (Solanumtuberosum L.) irrigated
with a subsurface drip system, under the semi-arid climate of central Tunisia.
Experiments were carried out during three growing seasons (2012, 2014 and 2015) at the High Agronomic
Institute of ChottMariem in Sousse, by considering different planting dates and irrigation depths, the latter
scheduled according to the climate observed during the season. All the considered treatments received the same
pesticide and fertilizer management.
Experiments evidenced that the climatic variability characterizing the examined seasons (photoperiod, solar
radiation and average temperature) affects considerably the crop phenological stages, and the late sowing shortens
the crop cycle.It has also been demonstrated that Leaf Area Index (LAI) and crop yield resulted relatively
higher for those treatments receiving larger amounts of seasonal water. Crop yield varied between 16.3 t/ha and
39.1 t/ha, with a trend linearly related to the ratio between the seasonal amount of water supplied (Irrigation,
I and Precipitation, P) and the maximum crop evapotranspiration (ETm). The maximum crop yield was in
particular obtained for a value of this ratio equal to 1.45. Moreover, when increasing the seasonal pluviometric
deficit (P-ETm) and therefore the irrigation depth (I), standard deviations of crop yield tended to decrease, as a
consequence ofthe more uniform soil water content in the root zone.
In terms of agronomic water use efficiency (AWUE),differences among the investigated treatments varied in
a quite narrow range,due to thecombined effects of seasonal precipitation and atmospheric water demand on
irrigation depths and crop yield.On the other hand, when considering irrigation water use efficiency (IWUE), more
relevant differences between treatments were observed,being the higher values of IWUEgenerally associated to
the lower irrigation depths. However, to define the best irrigation management strategy it is necessary, from one
side, to consider the availability of water and from the other, to perform aneconomic analysis accounting for the
cost of water and the related benefits achievable by the farmer
Irrigation management strategies to improve Water Use Efficiency of potatoes crop in Central Tunisia
In Tunisia, the expansion of irrigated area and the semiarid climate make it compulsory to adopt strategies of
water management to increase water use efficiency. Subsurface drip irrigation (SDI), providing the application of
high frequency small irrigation volumes below the soil surface have been increasingly used to enhance irrigation
efficiency.
At the same time, deficit irrigation (DI) has shown successful results with a large number of crop in various
countries. However, for some crops like potatoes, DI is difficult to manage due to the rapid effect of water stress
on tuber yield. Irrigation frequency is a key factor to schedule subsurface drip irrigation because, even maintaining
the total seasonal volume, soil wetting patterns can result different during the growth period, with consequence
on crop yield. Despite the need to enhance water use efficiency, only a few studies related to deficit irrigation of
horticultural crops have been made in Tunisia.
Objective of the paper was to assess the effects of different on-farm irrigation strategies on water use efficiency
of potatoes crop irrigated with subsurface drip irrigation in a semiarid area of central Tunisia. After validation,
Hydrus-2D model was used to simulate soil water status in the root zone, to evaluate actual crop evapotranspiration
and then to estimate indirectly water use efficiency (IWUE), defined as the ratio between crop yield and total
amount of water supplied with irrigation.
Field experiments, were carried out in Central Tunisia (10◦ 33’ 47.0” E, 35◦ 58’ 8.1◦ N, 19 m a.s.l) on a potatoes
crop planted in a sandy loam soil, during the growing season 2014, from January 15 (plantation of tubers) to May
6 (harvesting). Soil water status was monitored in two plots (T1 and T2) maintained under the same management,
but different irrigation volumes, provided by a SDI system. In particular, irrigation was scheduled according to the
average water content measured in the root zone, with a total of 8 watering, with timing ranging between one and
three hours in T1, and between about half-an-hour and one-hour and a-half, in T2.
The validity of Hydrus-2D model was initially assessed based on the comparison between measured and estimated
soil water content at different distances from the emitter (RMSE values were not higher than 0.036). Then,
model simulations allowed to verify that it is possible to enhance irrigation water use efficiency by increasing
the frequency of irrigation even maintaining limited water deficit conditions during the full development stage
subsequent the crop tuberization. Experimental results, joined to model simulations can therefore provide useful
guidelines for a more sustainable use of irrigation water in countries characterised by semi-arid environments and
limited availability of water resources
Optimizing subsurface dripline installation depth with Hydrus 2D/3D to improve irrigation water use efficiency in the central Tunisia
The main objective of the work is to optimize drip installation depth for Eggplant crop irrigated with surface or subsurface drip irrigation systems to improve irrigation Water Use Effeciency (WUE), by means of field measurements and simulations carried out with Hydrus-2D model. Initially, a comparison between simulated Soil Water Contents (SWC) and the corresponding measured in two plots, in which laterals with coextruded emitters are laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose the best position of the lateral, the results of different simulation run, carried out by choosing a deeper installation (T45) depth. Simulated SWC’s resulted fairly close to the corresponding measured at different distances from the emitter and therefore the model was able to predict SWC’s in the root zone with values of the Root Mean Square Error generally lower than 4%. This result is consequent to the appropriate schematization of the root distribution, as well as of the root water uptake. The values of WUE associated to the different examined installation depths tend to a very slight increase when the position of the lateral is situated on 20 cm and start to decrease for the higher depths
Effects of Saline and Deficit Irrigation on Soil-Plant Water Status and Potato Crop Yield under the Semiarid Climate of Tunisia
Water supplies have been decreasing in several semi-arid regions, and it is therefore necessary to adopt irrigation strategies aimed at maximizing water use efficiency. In this paper, the effects of saline and deficit irrigation on water use efficiency and on potato crop response, based on observations of soil and plant water status, were investigated. Experiments were carried out in Central Tunisia, by monitoring potato crop growth during two seasons in four distinct treatments (T1–T4), represented by two different irrigation doses and two water qualities. For irrigation scheduling purposes, thresholds of soil matric potential, soil water content and Crop Water Stress Index (CWSI) were identified with the aim to quantify the effects of water and/or salinity stress on the achievable yield. Experiments allowed verifying that crop yield is strongly affected by the seasonal amount and quality of applied water. Despite differences of crop yield between treatments T2, T3 and T4 not being statistically significant (P < 0.05), crop yield varied between 26.3 t/ha (T3 in 2015) to 16.3 t/ha (T4 in 2015). However, crop yield decline of 17.0 t/ha and 12.0 t/ha per each 100 mm decrease of applied water were observed under the application of water electrical conductivity of 1.6 dS/m and 4.1 dS/m respectively. On the other hand, an increase of 1.0 dS/m in water electrical conductivity caused a yield decline rate of about 10%. The results achieved showed that under the semi-arid climate of Tunisia, potato crop irrigation should be scheduled to avoid water deficit; however, the possibility to reduce water supply can be envisaged when water availability is limited, but with the awareness to accept the shortage of production. Finally, when saline water is the only source available to the farm, it is necessary to avoid the reduction of irrigation doses, to prevent excessive salt accumulation in the root zone with unavoidable effects on crop yield
Assessing Hydrus-2D Model to Investigate the Effects of Different On-Farm Irrigation Strategies on Potato Crop under Subsurface Drip Irrigation
The objective of this paper was to assess the performance of Hydrus-2D model to simulate the effects of different on-farm irrigation strategies applied on potato crop. The ability of the model to simulate the stress coefficient (Ks), obtained as the ratio between actual and maximum transpiration, and to define the productive function of potato crop under the semi-arid conditions of central Tunisia were also evaluated. Experiments were carried out on potato crop under full (FI) and deficit irrigation (DI) and two different water qualities supplied by means of a subsurface drip irrigation system. Results evidenced that the model, despite some discrepancies locally observed, can fairly accurately predict soil water contents and electrical conductivity around buried emitters. Furthermore, under water and salt stress conditions, “measured” Ks, based on crop water stress index (CWSI) obtained on thermal images, resulted in a good correlation with the corresponding estimated by the model (R2 = 0.8). The database collected during the three growth seasons also allowed the definition of the crop productive function represented by a linear relationship between the relative yield loss and Ks. This function represents a useful guidelines for the sustainable use of irrigation water in countries characterized by a semi-arid climate and a limited availability of water for irrigation
Optimizing subsurface dripline installation depth with Hydrus 2D/3D to improve irrigation water use efficiency in the central Tunisia
The main objective of the work is to optimize drip installation depth for Eggplant crop
irrigated with surface or subsurface drip irrigation systems to improve irrigation Water
Use Effeciency (WUE), by means of field measurements and simulations carried out with
Hydrus-2D model. Initially, a comparison between simulated Soil Water Contents (SWC) and
the corresponding measured in two plots, in which laterals with coextruded emitters are
laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose
the best position of the lateral, the results of different simulation run, carried out by
choosing a deeper installation (T45) depth. Simulated SWC’s resulted fairly close to the
corresponding measured at different distances from the emitter and therefore the model was
able to predict SWC’s in the root zone with values of the Root Mean Square Error generally
lower than 4%. This result is consequent to the appropriate schematization of the root
distribution, as well as of the root water uptake. The values of WUE associated to the
different examined installation depths tend to a very slight increase when the position of
the lateral is situated on 20 cm and start to decrease for the higher depths
Optimizing subsurface dripline installation depth with Hydrus 2D/3D to improve irrigation water use efficiency in the central Tunisia
The main objective of the work is to optimize drip installation depth for Eggplant crop
irrigated with surface or subsurface drip irrigation systems to improve irrigation Water
Use Effeciency (WUE), by means of field measurements and simulations carried out with
Hydrus-2D model. Initially, a comparison between simulated Soil Water Contents (SWC) and
the corresponding measured in two plots, in which laterals with coextruded emitters are
laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose
the best position of the lateral, the results of different simulation run, carried out by
choosing a deeper installation (T45) depth. Simulated SWC’s resulted fairly close to the
corresponding measured at different distances from the emitter and therefore the model was
able to predict SWC’s in the root zone with values of the Root Mean Square Error generally
lower than 4%. This result is consequent to the appropriate schematization of the root
distribution, as well as of the root water uptake. The values of WUE associated to the
different examined installation depths tend to a very slight increase when the position of
the lateral is situated on 20 cm and start to decrease for the higher depths