Abstract
In this study, the authors analyzed the consequences of irrigation management strategies as an essential factor to save water and maintain high crop yields. The present research aimed at comparing coriander (Coriandrum sativum L.), cv. Verdão, yields under fertigation via drip irrigation with a continuous application and in pulses, with 40, 60, 80, 100 and 120% of the crop evapotranspiration (ETc) being recovered. These treatments were distributed in randomized blocks in a 2 × 5 factorial scheme, with three replications, in a greenhouse located at the Federal Rural University of Pernambuco, northeast Brazil (08°01′6.50″ S and 34°56′46″ W, average elevation 6.5 m). The continuous irrigation consisted of the application of water depth in a single daily event, while pulsed irrigation comprised the application of the same irrigation depth split up into five events with a 1-hour interval between pulses. Crop evapotranspiration (ETc) was determined via the water balance by lysimetric drainage. The fertilizers were applied in every watering. The biometric and productivity crop pointed that pulsed irrigation to a mean depth of 58% of the ETc corresponds to the results obtained with the application of the depth equivalent to 100% of the ETc by continuous irrigation, consequently with reduced input costs.
HIGHLIGHTS
Drip irrigation pulsed saves 40% water compared to continuous irrigation.
Frequency of watering and fertilization determines crop yield.
Pulsed fertigation provides higher fresh and dry mass with deficit irrigation.
Graphical Abstract
INTRODUCTION
Coriander (Coriandrum sativum L.) is a widely consumed herb in the northeast region of Brazil, especially in the form of green shoots, but also as ground seeds (Silva et al. 2012). Despite the economic and social importance of this region, coriander cultivation is still practiced in an empirical way (Cavalcante et al. 2016), with few studies that seek to optimize water and nutrient use.
Although India is the largest producer, consumer and exporter of spices in the world, mainly those known seed spices, as coriander (Meena et al. 2019; Tridge 2019), and Brazil is not among the largest world producers, the high consumption of coriander in the North and Northeast of Brazil allows the inference that the future production scenario is promising. Therefore, researches that explore the way of tillage, reduction of water consumption via irrigation and use of fertigation can subsidize the increase of the production area in a sustainable way. The information available is still incipient regarding the proper irrigation management and specifically regarding the use of pulse drip fertigation. Menezes et al. (2020), in similar conditions to this study, evaluated the accumulation of nutrients in coriander under continuous and pulse drip fertigation depths, and observed that the highest accumulation of K, Mn, Cu and Zn were obtained with pulse fertigation combined with water depths lower than 100% ETc. In this sense, it is possible to define the most appropriate production strategies for coriander and other leafy vegetables, rationalizing use of agricultural inputs and reducing production costs.
The deficiency of knowledge about irrigation management techniques of the growers results in a low average yield of most vegetable crops; on the other hand, an increase in yields of drip irrigated vegetables has also been reported by several researchers (Imtiyaz et al. 2000; Jha et al. 2017; Silva et al. 2018). Water use optimization is necessary for northeast Brazil, especially in the semiarid region, where farmers are completely dependent on irrigation for plant growth. Besides that, cost reduction in terms of water, nutrients, energy and operational costs is important for the viability of agricultural businesses (Sandri et al. 2014). Therefore, the development of sustainable water use practices in agriculture is essential for the rationalization of food production.
A technique that increases the water and nutrient use efficiency is localized irrigation, applied in pulses; that is, instead of applying irrigation in a single event, it is divided into several events. Eid et al. (2013) comment that this favors the water movement in the horizontal direction, improving the distribution of soil moisture and increasing the wet soil volume in the root zone. In this sense, some researchers have also associated it with the use of lower depths for crop evapotranspiration, the so-known ‘deficit irrigation’. This statement is supported by the maintenance of soil moisture throughout the day being likely to be a suitable strategy to mitigate the harmful effects of deficit water and useful in times of limited water availability, mainly in semiarid regions (Martin et al. 2012; Eid et al. 2013; Phogat et al. 2013; Stallmann et al. 2020).
However, approaches of pulsed drip fertigation with soil water depletion are still scarce, although, in Brazil, some studies have been performed with pulse dripping on lettuce (Almeida et al. 2017), bean pod (Almeida et al. 2016) and coriander (Menezes et al. 2020). In Egypt, this approach has been tested in soybean and potato crops (Abdelraouf et al. 2012; Eid et al. 2013) as well the advantage of using composite conditioner with pulsed irrigation to reduce deep percolation and obtain a wide horizontal spread of wetting (Abd-elhakim 2019), while studies in Saudi Arabia have applied it to tomato crops (Elnesr et al. 2015).
This study evaluated the productivity of coriander (Coriandrum sativum L.), cv. Verdão, under five irrigation rates (40%–120% of estimated soil water depletion) and fertigated via a drip irrigation system in continuous and pulsed applications.
MATERIALS AND METHODS
The experiment was carried out between August and September 2017 in a greenhouse at the Federal Rural University of Pernambuco, Recife City, in northeast Brazil (08° 01′ 6.50″ S and 34° 56′ 46″ W, average elevation is 6.5 m above sea level). The local climate, as classified by Köppen, is As’ type, tropical hot and humid (Jales et al. 2012). Air temperature and relative humidity were monitored via an electronic sensor. The average maximum and minimum air temperatures registered were 34.35 and 25.66 °C, respectively, with average maximum air relative humidity of 92.22% and minimum of 55.90%.
The experimental design consisted of randomized blocks in a 2 × 5 factorial scheme, with three replicates, resulting in 30 experimental plots. Two types of water application (continuous and pulsed) and five ETc replacement depths (120, 100, 80, 60 and 40%) were evaluated. The experimental plots consisted of 30 masonry beds of 1.02 m2 (5.10 m (length) × 0.20 m (width) × 0.20 m (height)), waterproofed with polyethylene plastic film and with drainage tubes installed in the longitudinal direction of each bed. The sandy soil used in this experiment (Table 1) was characterized according to the methodologies of Teixeira et al. (2017).
Chemical and physical characterization of the soil
Chemical attributes . | |||||||||
---|---|---|---|---|---|---|---|---|---|
pH water . | Ca2+ . | Mg2+ . | Na+ . | K+ . | Al3+ . | Al + H+ . | P+ . | O.C.a . | O.M.b . |
cmolc dm³ | mg dm−3 | g kg−1 | |||||||
5.1 | 2.0 | 1.5 | 0.01 | 0.01 | 0.2 | 4.68 | 2.0 | 5.62 | 9.69 |
Physical attributes . | |||||||||
Sand . | Loam . | Clay . | Pdc . | Bdd . | θfce . | θpwpf . | . | . | . |
g kg−1 | kg dm−3 | m3 m−3 | |||||||
904 | 32 | 64 | 2.5 | 1.5 | 0.10 | 0.09 |
Chemical attributes . | |||||||||
---|---|---|---|---|---|---|---|---|---|
pH water . | Ca2+ . | Mg2+ . | Na+ . | K+ . | Al3+ . | Al + H+ . | P+ . | O.C.a . | O.M.b . |
cmolc dm³ | mg dm−3 | g kg−1 | |||||||
5.1 | 2.0 | 1.5 | 0.01 | 0.01 | 0.2 | 4.68 | 2.0 | 5.62 | 9.69 |
Physical attributes . | |||||||||
Sand . | Loam . | Clay . | Pdc . | Bdd . | θfce . | θpwpf . | . | . | . |
g kg−1 | kg dm−3 | m3 m−3 | |||||||
904 | 32 | 64 | 2.5 | 1.5 | 0.10 | 0.09 |
aOrganic carbon.
bOrganic matter.
cParticle density.
dBulk density.
eField capacity.
fPermanent wilting point.
Due to the acidic condition of the soil, acidity needed to be corrected with the application of limestone. Mineral fertilization was performed with phosphorus, P-fertilization, in planting (simple superphosphate -SSP) according to the recommendations of Cavalcanti (2008), and the other nutrients were applied daily via fertigation (Furlani 1998). The continuous irrigation consisted of the application of the calculated depth once a day; irrigation in pulses consisted of dividing to the same depth into five applications a day, with an interval of 1 hour between pulses. The fertilizers were applied in every watering. The crop evapotranspiration (ETc) replacement depths were calculated supported by drainage lysimeters, installed in the experimental environment (Figure 1). The daily water consumption (ETc) was calculated by subtracting the volume of water collected as drainage during a 24-h period from the amount that was supplied by irrigation depth during the same period. Treatments started on the 10th day after sowing; until then, 100% of the ETc was applied (Table 2).
Irrigation depth applied per treatment
Depth (mm) . | Etc . | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
120% . | 100% . | 80% . | 60% . | 40% . | ||||||
Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | |
Initiala | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 |
Treatmentb | 105.6 | 105.6 | 88.0 | 88.0 | 70.4 | 70.4 | 52.8 | 52.8 | 35.2 | 35.2 |
Totalc | 124.8 | 124.8 | 107.2 | 107.2 | 89.6 | 89.6 | 72.0 | 72.0 | 74.4 | 74.4 |
Depth (mm) . | Etc . | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
120% . | 100% . | 80% . | 60% . | 40% . | ||||||
Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | Pulse . | Cont. . | |
Initiala | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 | 19.2 |
Treatmentb | 105.6 | 105.6 | 88.0 | 88.0 | 70.4 | 70.4 | 52.8 | 52.8 | 35.2 | 35.2 |
Totalc | 124.8 | 124.8 | 107.2 | 107.2 | 89.6 | 89.6 | 72.0 | 72.0 | 74.4 | 74.4 |
aTotal depth applied in the first 10 days after sowing.
bTotal depth applied from the tenth to the thirty-fourth day after sowing.
cTotal depth applied during the cycle.
Schematic diagram of non-weighting drainage lysimeter design: pot design and collecting container.
Schematic diagram of non-weighting drainage lysimeter design: pot design and collecting container.
The gross irrigation depth (d gross) was the product of ETc and the efficiency of the irrigation system. The irrigation time was obtained considering the space occupied by each plant, the average flow of the dripper and the number of emitters per plant. The gross irrigation depth and the irrigation application times for each treatment were determined automatically using an electronic controller, commanded by ARDUINO. Thus, via a programming code, the relays were switched on, which turned on the solenoid valves, applying the required irrigation depth according to the treatments.
The same water quality and composition of the nutritive solution, according to Furlani (1998), have been used in all treatments; a single 1,000-L reservoir was filled with a nutritive solution with an initial electrical conductivity of 2.5 dS m−1. The drip irrigation system used was composed of one drip hose (outside diameter – OD: 16 mm) per plot with non-pressure compensating (NPC) drippers spaced 0.30 m apart, with a nominal flow of 0.60 L h−1 and a 120-mesh disk filter. The pressurizing system consisted of one 0.5-cv centrifugal pump motor to keep the service pressure at 10 mwc (meters of water column), according to the manufacturer's recommendation.
Water distribution uniformity was evaluated twice, at the beginning and the end of the experiment, following the methodology described by Merriam & Keller (1978). The sampling flow used four drippers per lateral line: the first emitter, the emitters placed in the center of the lateral line, and the last emitter, with a collection time of twelve minutes measured in a digital chronometer. The mean flow measured in the drippers was 0.55 L h−1, and the water distribution uniformity was 98.20% at the beginning and 97.09% at the end of the experiment, indicating high uniformity.
Sowing of coriander (Coriandrum sativum L.), Verdão cultivar, was performed directly in the experimental plots, with 20 seeds per pit, spaced at 0.10 m between rows and 0.15 m between plants, and to control border effects the useful area was 0.12 m2. Ten days after sowing, thinning was performed, leaving six plants per pit. Throughout the crop development, weeds were controlled manually. Although there was no presence of diseases, pests, such as caterpillars and aphids, were controlled with a single dose of the contact insecticide Decis®.
At 35 days after sowing, the following variables were analyzed: (i) fresh and dry mass of shoot and root, using a precision scale (0.001 g) and after drying of the fresh material in a forced ventilation oven at 65 °C until reaching constant weight; (ii) percentage of the shoot and root dry mass (% SDM and % RDM, respectively), based on the ratio between dry and fresh mass; (iii) height of the plant, average values of the useful area and measurement from the base of the stem until the last leaf; and (v) crop productivity in terms of fresh mass production (shoot + root) per square meter.
The analysis of variance (ANOVA) was used to determine whether the means were different, using the F test. Regression analysis was used to compare the quantitative factors, and the agglomerative test of Scott Knott averages was applied with a significance threshold of 0.05 for the qualitative factors. For all analyses, we used the statistical software package SISVAR (Ferreira 2011).
RESULTS AND DISCUSSION
There was a significant effect (p < 0.01) of the type of application and irrigation depth on the percentage of root dry mass (% RDM). For the percentage of shoot dry mass (% SDM) the effect was significant (p < 0.01) only for the irrigation depth. For shoot and root fresh mass (SFM and RFM, respectively), shoot and root dry mass (SDM, RDM), plant height and yield (Y), there was a significant effect (p < 0.01) for the interaction between the two factors. The coefficients of variation were lower than 19%, indicating adequate uniformity in the experiment.
Under continuous irrigation, shoot fresh mass (SFM) increased linearly at a rate of 14.17 g m−2 to 120% of the ETc, while under pulsed irrigation the maximum yield (1,621.80 g m−2) was reached with irrigation depth equivalent to 88.42% ETc. However, we highlight that above 100% of ETc, there was no difference (p > 0.05) in the SFM under continuous irrigation or pulse irrigation (Figure 2(a)). On the other hand, under continuous application of irrigation depth equivalent to 100% ETc, the crops produced an estimated SFM of 1,222.67 g m−2, while under pulse irrigation, the same yield was obtained with depth irrigation equivalent to 58.28% ETc, which resulted in saving 41.71% of the water volume required per crop cycle, equivalent to 446.96 m3 ha−1 (Figure 2(a)). In contrast, Linhares et al. (2015) and Aguiar et al. (2015) verified a maximum SFM of 645.30 g m−2 (6,453 kg ha−1) and 1,197.80 g m−2 (11,978 kg ha−1) for the same cultivar at 35 and 36 days after sowing, respectively.
Shoot and root fresh (a and b) and shoot and root dry mass (c and d), percentage of shoot dry mass (e) and root dry mass (f), the height of plants (g), and coriander cv. Verdão yield (h), under irrigation levels applied via drip irrigation system with and without pulses. Different letters indicate significant differences between the continuous irrigation and pulsed irrigation (Scott Knott test, P < 0.05).
Shoot and root fresh (a and b) and shoot and root dry mass (c and d), percentage of shoot dry mass (e) and root dry mass (f), the height of plants (g), and coriander cv. Verdão yield (h), under irrigation levels applied via drip irrigation system with and without pulses. Different letters indicate significant differences between the continuous irrigation and pulsed irrigation (Scott Knott test, P < 0.05).
Under continuous irrigation, root fresh mass (RFM) was increased up to 120% of the ETc, at a rate of 1.53 g m−2 at each 10 mm added to the fertigation depth, distinguishing (p < 0.01) data obtained when pulsed irrigation was used, except under 40% ETc (Figure 2(b)). When irrigation occurred via pulses, the maximum RFM was 208.75 g m−2 under the estimated depth at 86.46% of ETc. In another analysis, under the ETc estimated at 56.92%, the plants produced the same RFM (153.96 g m−2) observed when 100% ETc under continuous irrigation was applied (Figure 2(b)).
At the SFM and RFM of the treatments under depth lower than 100% of the ETc, pulsed irrigation resulted in higher value when compared to continuous irrigation. These results point that this irrigation strategy optimizes water and nutrient use in the fertigation process, as also verified by Assouline et al. (2012) and Warner et al. (2009), who explained this result with the high nutrient availability and water absorption.
The shoot (SDM) and root dry mass (RDM) showed similar results, with an increase of 1.40 and 0.12 g m−2, respectively, at each increment of 10 mm in the fertigation depth when applied continuously up to 120% of ETc. The SDM and RDM data obtained under 100% ETc (129.75 and 15.25 g m−2, respectively) were obtained with a depth estimated at 57.00 and 57.25% of ETc when pulsed irrigation was used. As a result, the maximum SFM and RFM yield increased by 170.42 g m−2 (87.88% ETc) and 19.04 g m−2 (83.75% ETc), respectively (Figure 2(c) and 2(d)).
Aguiar et al. (2015) obtained, for the cultivar Verdão (161.40 g m−2), a maximum SDM value of 161.40 g m−2 at 36 days after sowing under organic fertilization. In the present research, the maximum SDM was 73.4% of the ETc under pulsed fertigation. Eid et al. (2013) suggest that the increase of the wet bulb in the root zone may favor nutrient absorption and, consequently, the increase in SDM and RDM in irrigation depths less than 100% of ETc. Therefore, the response of the plants to pulsed irrigation (SFM, RFM, SDM, and RDM) indicates the reduction of input costs, such as costs of water, nutrients, electrical energy, and maintenance, up to the depth that maximizes production; in this case, less than 100% of ETc.
The reduction of % SDM and the % RDM at the ratio of 0.17 and 0.259% for each 10-mm increase in the ETc replacement may be associated with the increase in the water content at a ratio higher than the dry mass gain, which was also favored by the greater water and nutrient availability (Figure 2(e) and 2(f)). Continuous irrigation technique increased % RDM, suggesting lower dry mass gain. Sousa et al. (2017), exposing sorghum to different irrigation depths, also verified a reduction in the percentage of leaves dry mass with the increase of the irrigation depth; similarly, Delazari et al. (2017) reported a positive increase in the % RDM of sweet potato until reaching a maximum depth, with a subsequent decrease.
Plant height was higher (p < 0.01) under pulsed irrigation to irrigation depth at 40 and 60% of ETc compared to continuous irrigation. However, under 100% of the ETc, plant height of 18.82 cm was reached under continuous fertigation; this same plant height was obtained with 60.84% of ETc applied via pulses (Figure 2(g)). On the other hand, the estimated depth at 81.29% of ETc, when pulse irrigation was applied, resulted in the maximum plant height (19.61 cm). Lower values were obtained by Linhares et al. (2015) when evaluating organic fertilization, obtaining a maximum plant height of 18.10 cm at 35 days after sowing for the same cultivar. Other authors studying the same cultivar obtained higher plant height values. For example, Aguiar et al. (2015) evaluated the production of coriander grown with organic compounds and obtained a plant height of 31 cm for the highest fertilization dose at 36 days after sowing. Pereira et al. (2015) evaluated coriander cultivar performance as a function of irrigation management in a semiarid region and obtained a maximum plant height of 40.75 cm at 40 days after sowing. Marsaro et al. (2014), evaluating coriander cultivar yields under greenhouse and field conditions, report a mean plant height of 29.16 cm at 43 days after sowing. Angeli et al. (2016), assessing the production and water use efficiency in coriander under irrigation and nitrogen fertilization, reported a plant height of 43 cm for the applied dose of 105 kg ha−1 of N, not indicating the variety used. Rajasekar et al. (2013), evaluated the influence of a growing environment (shade net house and open field), observing a mean plant height of 34 and 24 cm in the shade net and open conditions, respectively.
Comparing the results obtained in the present research with the data described above, the higher results found in the other studies are most likely due to the application of chemical fertilizers to stable soils. Besides that, under field conditions, cultivation time was up to 43 days. Another important factor to consider is that all other trials, except Marsaro et al. (2014), were established in the open field, where the direct solar radiation allows a better photosynthetic activity and, therefore, a greater formation of photoassimilates.
Coriander productivity was higher (p < 0.01) when irrigation was lower than 100% of the ETc and applied in pulses compared to continuous irrigation. As a result, the maximum productivity (1.84 kg m−2) was reached under the estimated depth of 88.60% of the ETc, while under continuous irrigation with 100% of the ETc, crop productivity was 1.37 kg m−2. This result could be obtained with pulsed irrigation to an estimated depth of 57.85% of the ETc (Figure 2 h).
Some authors (Linhares et al. 2014; Marsaro et al. 2014) have obtained lower yields with the same cultivar when compared to the yields observed in this study, while others (Maciel et al. 2012; Angeli et al. 2016) have obtained higher yields. Although these results were obtained under different experimental conditions and harvesting times, the maximum productivity at a depth lower than 100% of the ETc, presented here, serves as a guideline for the establishment of management strategies to optimize water and nutrient use (Assouline et al. 2012).
Drip pulse irrigation management can increase efficiency and reduce nutrient losses in irrigated vegetable fields. The split irrigation of the necessary daily depth is feasible as it provides good practice to save water, energy and nutrients. In the case of the coriander crop, according to our results, adopting 60% of the ETc applied in pulses with an interval of 60 minutes between two pulses is a good irrigation management strategy for greenhouse conditions.
Further investigations are, however, necessary to identify the methodology and/or protocol to define the number of pulses and time between two successive pulses, considering dripper flow, crop, soil, and local climate. Besides that, identify the possibility of using similar management with other crops, with brackish water, fertigation, and apply successive cycles with deficit irrigation and the application of a leaching depth between cycles.
CONCLUSIONS
- 1.
Pulsed fertigation is recommended for coriander crop and provides higher shoot and root values of fresh and dry mass as well as plant height and yield values, with ETc replacement of less than 100%.
- 2.
The reduction in input costs, such as costs for water, nutrients, electric energy, and maintenance, in the production of coriander can be obtained by adopting pulsed irrigation, because maximum production is reached with less than 100% of the ETc.
- 3.
The biometric and productivity variables showed that pulsed irrigation to a mean depth around 60% of the ETc corresponds to the results obtained with the application of the depth equivalent to 100% of the ETc by continuous irrigation.
ACKNOWLEDGEMENT
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) - Finance Code 001.
CONFLICT OF INTEREST
On behalf of all authors, the corresponding author states that there is no conflict of interest.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.