Water relations and productivity of sugarcane irrigated with domestic wastewater by subsurface drip

Agricultural Water Management 185 (2017) 105–115

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Water relations and productivity of sugarcane irrigated with domestic wastewater by subsurface drip Gonc¸alves I.Z. a,∗ , Barbosa E.A.A. b , Santos L.N.S. c , Nazário A.A. d , Feitosa D.R.C. e , Tuta N.F. e , Matsura E.E. f a

Agricultural Engineering, Water for Food Institute, University of Nebraska, Lincoln, NE, United States Agricultural Engineering, University of Ponta Grossa, Ponta Grossa, PR, Brazil c Agricultural Engineering, Goiano Federal Institute, Rio Verde, GO, Brazil d Agricultural Engineering, Federal Institute of Education, Science and Technology of the Sertão of Pernambucano, Recife, PE, Brazil e Agricultural Engineering, University of Campinas, Campinas, SP, Brazil f Agricultural Engineering, Faculty of Agricultural Engineering, University of Campinas, Campinas, SP, Brazil b

a r t i c l e

i n f o

Article history: Received 29 September 2016 Received in revised form 9 January 2017 Accepted 28 January 2017 Keywords: Gas exchange Domestic sewage Water reuse Saccharum officinarum L.

a b s t r a c t The water scarcity is one of the main factors contributing to the reduction of productivity in agricultural crops, and the use of alternative water source in the irrigation is an option to minimize water stress. The objective of this study was to evaluate the water relations, vegetative growth, productivity and technological quality of sugarcane irrigated with treated domestic sewage by subsurface drip during its second ratoon. The research was performed at the School of Agricultural Engineering of the State University of Campinas—SP, through a randomized block design with five treatments, with two depths of dripper lines installation and two water sources, which are: irrigation with wastewater from domestic sewage applied to 0.20 m depth, and to 0.40 m, irrigation with fresh water from a surface reservoir to 0.20 m depth and to 0.40 m and finally non-irrigated plots. Irrigation management was performed following the soil water balance through the time-domain reflectometry technique and all irrigated treatments were fertigated according to the water source applied. Leaf water potential, chlorophyll, gas exchange, leaf nutrition, vegetative growth, productivity and quality technological were measured during the second ratoon of sugarcane. Soil moisture changed according to the depth of the dripper lines installation, being higher for irrigated treatments. The leaf water potential, chlorophyll, gas exchange and nitrogen and magnesium concentration in the leaves also were higher for irrigated plots. The irrigated treatments with sewage had the largest stem and sugar yield compared with the rainfed, being the dripper line irrigated with sewage to 0.20 m presenting the greatest differences reaching 95% and 86% with a productivity of 233.69 Mg ha−1 and 37.06 Mg ha−1 for stem and total recoverable sugar, respectively; however, there were not significant differences between the irrigated plots. The technological quality of sugarcane was considered appropriate to all treatments. Published by Elsevier B.V.

1. Introduction The sugarcane is originally from Southeast Asia, however, mainly due to edaphoclimatic conditions and areas available, Brazil became the world’s largest producer, with an estimated area

∗ Corresponding author. E-mail addresses: [email protected] (I.Z. Gonc¸alves), [email protected] (E.A.A. Barbosa), [email protected] (L.N.S. Santos), [email protected] (A.A. Nazário), [email protected] (D.R.C. Feitosa), natalia1 [email protected] (N.F. Tuta), [email protected] (E.E. Matsura). http://dx.doi.org/10.1016/j.agwat.2017.01.014 0378-3774/Published by Elsevier B.V.

planted to the harvesting 2016/2017 of 9 million hectares with almost 700 million tons total. However, most crops are rainfed, which makes the national average productivity be considered low (76 Mg ha−1 ) in relation to irrigated crops, pushing the expansion of sugarcane to new areas to supply the demand for biofuel and sugar influenced by population growth (CONAB, 2016). Several studies in Brazil shows irrigation increases the sugarcane productivity in relation to non-irrigated crops, as verified by Bastos et al. (2015) at Midwest, Pires et al. (2013) at Southeast and Oliveira et al. (2011) at Northeast. This is because the water has a import role on the plant metabolism and its unavailability in the soil causes the reduction of leaf water potential, decreasing the gas exchange and negatively affecting the assimilation of CO2 in chloro-

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plasts, limiting the production of assimilates to the development and production of sucrose (Taiz and Zeiger, 2013). Gonc¸alves et al. (2010) observed a significant reduction in stomatal conductance, transpiration, photosynthesis and water-use efficiency for nonirrigated plots in several sugarcane varieties under water stress in Brazil. However, the lack of rainfall and the water resources scarcity for irrigation in recent years at the largest Brazilian producer centers of sugarcane (center-south of the São Paulo State) has been aggravated, and there is no water sufficiently available to the irrigation to supply the crop water demand throughout your growing season. According Doorenbos and Kassam (1994), sugarcane needs 1500–2500 mm of water to the entire cycle. Given the above, a water alternative for irrigation to increase the productivity in sugarcane would be the use of treated domestic wastewater reuse (TDW), which in addition to providing savings on water and fertilizer also avoids the contamination of aquatic environment, keeping the fresh water for human and animal consumption, preserving still the fauna and flora aquatic of this waste (Thapliyal et al., 2013). On the other hand, depending on the volume and irrigation frequency, TDW can adversely affect the agricultural production due to its high concentration of nutrients and salts, which reduces the water availability for the plants from the reduction in water potential in the root zone. The stress caused by Na+ in the plant causes an antagonistic effect on K+ , reducing its concentration mainly in the leaves (Blumwald, 2000), affecting the regulation of opening and stomatal closing (Taiz and Zeiger, 2013) and consequently the productivity. In a study done by Leal et al. (2009), the TDW increased the Na+ concentration in an Oxisol cultivated with sugarcane after 16 months under subsurface drip irrigation (SDI) with application of different effluent levels (from 100% to 200% the crop water demand); however, the productivity of irrigated treatments were statistically higher than without irrigation. Among the different irrigation methods, the SDI appears as the safest to the application of TDW to crops, because it allows to apply the effluent directly on the root zone at low flow rates and high frequency reducing the leaching and evaporation, increasing the absorption efficiency of nutrients and water (Yao et al., 2011) thereby preventing the contamination of groundwater and the contact with the external environment, as well as keeps a superficial portion of the soil relatively dry reducing weeds development. In this regard, Charlesworth and Muirhead (2003) argue one of the most noted aspects is the proper installation depth of the dripper lines considering the structure and soil texture, and also the pattern of development of the root system. Historically in Brazil, vinasse (waste from the ethanol production) is the residue commonly applied as alternative nutrient source in sugarcane, mainly due to short distance between cultivated areas and sugar–ethanol mills (De Resende et al., 2006). In relation to the TDW, despite being a water source potential in Brazil, its using is not applied to the irrigation of sugarcane, mainly due to lack of research that ensure the sustainability of its application in food production. The objective of this study was to evaluate the water relations, vegetative growth, water quality, productivity and technological quality of sugarcane irrigated with treated domestic wastewater by subsurface drip during the second ratoon (third growing season).

620 m. This research is part of a pilot study with TDW application by SDI located in the largest sugarcane producing region of the world (south-central Brazil). According to the Köppen climate classification (Peel et al., 2007), the climate is subtropicaltropical (Cwa/Cfa), with an average annual temperature of 22.3 ◦ C, relative humidity annual average of 62% and total annual rainfall of 1425 mm. The soil of the experimental area is an Oxisol (Jacomine, 2009). The climatic parameters were obtained from automatic weather station located 50 m from the growing area. The variety cultivated was RB867515, which is the most planted in Brazil since 2007 (CTC, 2012). Planting was performed in May 2011, with 15 to 18 buds per linear meter, with planting depth of 0.30 m grown in three double rows per experimental plot, considering the two outermost lines as borders with the center one as the main line. Spacing between the center of the double rows (consisting of two rows spaced at 0.4 m apart) was 1.8 m. Thus, each experimental plot consisted of 97.2 m2 (5.4 × 18 m) totaling a total area of 2430 m2 (25 plots). Two water sources to irrigation were applied: fresh water from surface water reservoir (SWR) with 1140 m3 of capacity and TDW obtained from the sewage treatment system located at the experimental field. The sewage treatment system is constituted by anaerobic reactor of 4.19 m3 compartmentalized, and then through pipes, the sewage was pumped up to six wetlands cultivated with macrophytes with total volume of 2.3 m3 (2.7 m × 1.7 m × 0.5 m, length, width and depth, respectively). Subsequently, the domestic wastewater was pumped to the control head, and finally applied to the crop by an automatic pumping system. The experimental design was randomized blocks, in a double factorial plus additional treatment (2 × 2 + 1), two installation depths of the dripper line; two water sources and a non-irrigated treatment, totaling five treatments, being: irrigation with domestic sewage applied to 0.20 m depth (S20), and to 0.40 m (S40), irrigation with fresh water from a surface reservoir to 0.20 m depth (W20) and to 0.40 m (W40) and finally non-irrigated plots (NI). Since planting in 2011, the crop has been irrigated by following these treatments. For individualizing each treatment, we installed on the control head, two sets of pressurized systems, one for each water source (Fig. 1). All irrigated treatments were fertigated with mineral chemical fertilization by following the absorption rate of nutrients by the sugarcane according to Haag et al. (1987), complementing the nutrients already applied by the TDW and SWR. Thus, after passing through the control head, we collected every two months until the end of irrigation (early June/2014), samples of TDW and SWR to perform the physical, chemical and microbiological analysis (APHA, 2012) to sodium (Na), calcium (Ca), magnesium

2. Materials and methods 2.1. Study area and experimental design The study was performed in the experimental field at the Faculty of Agricultural Engineering of the State University of Campinas, Campinas—SP, located at 22◦ 53 S and 47◦ 05 W at an altitude of

Fig. 1. Control head for two sets of pressurized systems, one for each water source. TDW: treated domestic wastewater, SWR: surface water reservoir.

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(Mg), manganese (Mn), zinc (Zn), sulfur (S), iron (Fe), boron (B), potassium (K), total phosphorus (Pt), total nitrogen (Nt), biochemical oxygen demand (BOD), electrical conductivity (EC), hydrogen potential (pH), fecal coliforms (FC) and Escherichia coli (EC). From the Ca, Mg and Na were calculated sodium adsorption ratio (SAR). The results of the average quality of each water source were analyzed according its restriction on the use by following Ayers and Westcot (1994). Fertilizer injection was realized by venture method, twice a week until definitive suspension of irrigation, at doses of 120, 40 and 80 kg ha−1 for N, P2 O5 and K2 O, respectively, for N (calcium nitrate), P2 O5 (MAP) and K2 O (potassium sulfate). The fertilization to the non-irrigated plots was performed in a single topdressing between the planting rows (0.40 m), and the nitrogen source applied was urea for high productivity. 2.2. Irrigation system and management The dripper line used was integral pressure-compensating and anti-siphon mechanism dripper, it was buried in the center of the double lines in two depths (0.20 or 0.40 m), with spacing every 0.65 m and flow of 1.6 L h−1 . Through the soil water balance, the soil water content was maintained in the effective depth of the root system close to field capacity (0.35 cm3 cm−3 ) using the time-domain reflectometry technique (TDR), with previous calibration on the soil of the experimental field (Souza et al., 2006) with R2 of 98%. We used the equipment TDR 100 with RS232 interface and CR1000 data collector reads the electromagnetic signal automatically. Five probes were installed in each treatment at central blocks, the first probe was installed on the first dripper from the first 2 m away from boundary of the effective line. The probes were installed with a distance of 0.15 m from each other in the longitudinal direction, following the depths of 0–0.20; 0.20–0.40; 0.40–0.60; 0.60–0.80 and 0.80–1.0 m, monitoring the soil moisture on the root zone of sugarcane, as shown in Fig. 2. From the soil water balance, measured by the difference between the water content read by the TDR technique and max-

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imum water storage obtained by Richards pressure chamber method (Camargo et al., 2009), it was be inferred the quantity of water applied to each treatment separately (Eq. (1)). Vi = (Fc − i ) × (Zs × Flg × Cf ) × Nl

(1)

where Vi is the volume irrigated by treatment (m3 );  i is the water content measured by TDR (m3 m−3 );  Fc is the field capacity (0.35 m3 m−3 ); Zs is the depth exhibited by probe (up to 0.60 m); and Flg is the wet bulb width, 0.5 m, according to Elaiuy et al. (2015). The irrigations were performed twice a week up to two months before harvesting for sucrose accumulation in stems, the harvest was held in late August 2014. 2.3. Climate and irrigation applied Observed an atypical period to the climate at the experimental field, with low rainfall and irregularly distributed along the growing season, with summer and dry winter (Fig. 3). The total precipitation was 684.06 mm, representing only 48% of the average volume of the historical series. The average temperature throughout the second ratoon was 22.8 ◦ C, similar to the average of the historical series (22.3 ◦ C) having the highest average temperature values (27.42 ◦ C) and ETo (139.3 mm) in February 2014. August was the only month that there was no precipitation event, and for sugarcane lack of rains in this period was very important for the sucrose accumulation by the stems during the maturation phase (June and August). The applied depth is shown in Fig. 4. Due to insufficient TDW volume produced between December/2013 and February/2014, which was influenced by an high demand for irrigation (seen lower volumes precipitated in this period), there was need of supplementing with SWR the irrigated treatments with TDW. However, it is emphasized applied depths of different water sources were properly tabulated for each treatment, in order to avoid errors in calculations of fertigation. Thus, 155.1 mm of SWR and 228.4 mm of TDW were applied for S20 and SWR 167.4 mm of SWR and 246.5 mm of TDW for S40. The treatments in decreasing order of irrigated volume were: S40 > S20 > W40 > W20 with 414; 384; 333; and 313 mm, respectively. 2.4. Evaluations

Fig. 2. TDR probes installation in the soil profile for irrigation management. Z: installation height of line dripper (0.20 or 0.40 m).

Evaluations of gas exchange were performed with a portable infrared gas analyzer, photosynthetic photons flux density set at 2000 ␮mol m−2 s−1 and CO2 concentration set at 380 ppm. The measurements of physiological parameters were performed at the middle third of the leaf blade, unshaded and physiologically mature (+2), one day after irrigation and in days without cloud cover, from at 12:00 p.m. to at 14:00 p.m. The parameters measured were net photosynthesis (A, ␮mol m−2 s−1 ), stomatal conductance (Gs, mol m−2 s−1 ), leaf transpiration (E, H2 O mmol m−2 s−1 ). Through data measured estimated the water use efficiency (WUE = A/E). The measurements were performed at 81, 100, 113, 140, 163, 169, 225 and 260 days after harvesting (DAH) of the first ratoon (second growing season). It was also measured with TDR technique the soil moisture at 225 and 260 DAH (one day after the irrigation together with gas exchange measurement) to analyze its distribution in the soil profile up to 1.0 m depth every 0.20 m, and then analyze the relationship between the different depths of dripper lines installation and soil moisture, and how it can affect the soil–plant–atmosphere relationships. Chlorophylls a, b and a + b were measured by the indirect chlorophyll method. The determination of chlorophyll was held on five plants (leaf +2) in each plot, with two measurements per leaf and

160

40

120

30

80

20

40

10

Temperature (T, °C)

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Deph (mm)

108

0

0 Sep-13 Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Aug-14 Precipitation

ETo

T-High

T-Low

T-Average

Fig. 3. Monthly climate characterization for second sugarcane ratoon. ETo: reference evapotranspiration.

SWR

675 450 225 0 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40 S20 S40 W20 W40

Irrigation applied (mm)

TDW 900

Nov-13

Dec-13

Jan-14

Feb-14

Mar-14

Apr-14

May-14

Jun-14

Fig. 4. Irrigation applied to the different treatments adopted for second sugarcane ratoon. S20: treated domestic sewage applied to 0.20 m; S40: treated domestic sewage applied to 0.40 m; W20: surface water reservoir applied to 0.20 m; W40: surface water reservoir applied to 0.40 m.

thereby getting an average Falker Chlorophyll Index (FCI). The measurements were performed at 83, 113, 155, 183, 225 and 268 DAH of the first ratoon. The leaf water potential ( w MPa) was measured in two different periods of the sugarcane vegetative growth at 110 DAH (before development of the stems) and 160 DAH (intense vegetative development) in six plants per treatment collected at the central blocks. The  w was determined by Scholander pressure chamber, leaf +2 was used. For each treatment, the measurements were taken at 05:00 a.m. (pre-dawn, minimal leaf transpiration) and at 12:00 p.m. (noonday sun) one day after irrigation. Nutritional status of sugarcane was measured collecting leaf samples (leaf +1) of 10 plants per experimental plot (composite samples) for each one of the five planting blocks in the fourth month after the beginning of regrowth, the first and last third of the leaf were eliminated keeping only the leaf middle third, the midrib was also discarded, then the leaves were placed in a forced circulation air oven at 65 ◦ C until constant weight, dry leaves were milled and analyzed the concentrations of nitrogen, phosphorus, potassium, sodium, calcium and magnesium following the recommendations of Silva (2009). The sugarcane vegetative growth measurements were performed 73, 112, 136, 171, 201, 261 and 281 DAH in three plants (replications) for each plot. It performed the visual counting of tillers number in each double line for one linear meter. Stem diameter was measured at three points of the plant using a digital caliper (upper, middle and lower stem always in the middle of the internode) and then measured with a measuring tape in mm scale the stem length from the ground level until the first visible leaf auricle, thereby calculating the volume of stems per plant. The plant height was measured from the ground level to +1 leaf auricle. Leaf area (LA) was measured counting the number of green leaves (at least 20% of the area of green leaf blade) considering only the leaves with visible auricles. It was also measured the length and leaf width (+3) with the measuring tape and adopted the rela-

tionship given by Hermann and Câmara (1986) to estimate the leaf area. Consequently, the leaf area index (LAI) was calculated by the ratio between leaf area and the area occupied by tiller. The sugarcane yield estimation (SYE) was performed in all treatments through the collecting of five stems per plot on the five experimental blocks, and considering the number of tillers was possible to estimate the productivity in Mg ha−1 . Taking advantage of these samples were also performed the technological analysis for soluble solids content of the juice (Brix), apparent sucrose of the juice (Pol), purity apparent of the juice (PZA), content of fiber (F), total recoverable sugar (TRS), reducing sugars (RS) and from the TRS and SYE was estimated the theoretical yield of recoverable sugar (TYRS) per hectare. The results were submitted to analysis of variance by F test (ANOVA) at 5% probability in a randomized blocks design with double factorial and an additional treatment (Gomez and Gomez, 1984) being: two installation depths of the dripper line; two water sources and a non-irrigated treatment, totaling five treatments, and when significant, the means were compared by the Scott Knott test at 5% probability using Sisvar Software (Ferreira, 2011). 3. Results and discussion 3.1. Water quality Table 1 shows the average of water quality parameters applied in irrigation in the growing season with an average of four analyzes. The TDW showed concentrations higher than SWR for most nutrients, proving to be an important nutritional source for sugarcane especially when it comes to the macronutrients that are most required by the plants. Similar results were found in several studies, among them: Pereira et al. (2009), Blum et al. (2013), Gonc¸alves et al. (2013) and Freitas et al. (2012). According to Ayers and Westcot (1994), the TDW applied was classified with slight to moderate restriction on use in relation to

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Table 1 Average concentration of physical, chemical and biological parameters sources of water applied during the second ratoon sugarcane (December/2013 to June/2014). TDW6

Attribute −1

Total nitrogen (mg L ) Phosphorus (mg L−1 ) Potassium (mg L−1 ) Calcium (mg L−1 ) Magnesium (mg L−1 ) Sulfur (mg L−1 ) Sodium (mg L−1 ) Boron (mg L−1 ) Iron (mg L−1 ) Manganese (mg L−1 ) Zinc (mg L−1 ) Total chlorine (mg L−1 ) BOD1 (mg L−1 ) EC2 (dS m−1 ) SAR3 (mmol L−1 ) pH (H2 O) FC4 (MPN 100 mL−1 ) E. coli5 (MPN 100 mL−1 ) 1 2 3 4 5 6 7 8

78.9 70.1 27.5 28.0 4.05 25.7 59.8 0.13 0.55 0.08 0.09 <0.01 8.92 1.01 4.96 7.42 390187 39943

CV (%)7

SWR8

CV (%)

36.2 31.3 26.6 10.9 9.70 76.2 19.8 20.0 39.7 21.4 21.4 – 15.9 19.5 14.4 1.30 67.4 88.1

2.14 0.05 5.38 9.75 4.30 <0.001 7.66 <0.001 0.26 0.05 0.08 0.04 6.17 0.11 0.71 7.22 13.75 10.7

64.5 42.2 72.3 22.2 15.5 – 32.0 – 85.1 56.8 58.1 81.0 59.5 16.6 26.3 2.90 60.4 55.0

Biochemical oxygen demand. Electric conductivity. Sodium adsorption ratio. Fecal coliforms. Escherichia coli. Treated domestic sewage. Coefficient of variation. Surface water reservoir.

degree of irrigation water salinity (0.7 < EC < 3.0 dS m−1 ), providing 120.6 kg ha−1 on average for S20 and S40 of sodium on the soil, on the other hand, no restriction on use of the SWR (EC < 0.7 dS m−1 ). In relation to nutrients applied, 143.0, 279.9 and 72.0 kg ha−1 of N, P2 O5 and K2 O were applied in mean, respectively, considering S20 and S40 together meeting almost the nutrient total demand by the crop (100% of saving to N, 100% of saving to P2 O5 and 90% of saving to K2 O), on the other hand, the treatments irrigated with SWR did not add significant amounts of nutrients, being necessary to apply the nutrients by fertigation. According to Cavalcante et al. (2010), the sugarcane is classified as semi-tolerant to the exchangeable sodium in the soil; however, high salt concentrations in the irrigation water can affect the availability of water for the plants, because the soil water potential decreases with high concentrations of salts, which may reduce the plant development mainly for continuous application of TDW, generating great accumulation of salts, but this condition was not verified in the present study. 3.2. Water relations Regarding the availability of water in the soil profile, the results are shown in Fig. 5. Soil moisture on the treatment without irrigation was lower than other treatments, except to the layers 0.20–0.40 m and 0.80–1.0 m in the treatments with the dripper line buried to 0.40 m and 0.20 m, respectively, due the longer distance between the drippers and the layers, respectively. Thus, the installation depth of the dripper lines influenced soil moisture, because near the soil surface the treatments to 0.20 m presented higher moisture content (up to 0.40 m depth in the soil profile), on the other hand, lower moisture at depths when compared to irrigated treatments to 0.40 m (especially below 0.80 m in the soil profile). Santos et al. (2016) found installation of dripper line to 0.20 m in relation to 0.40 m depth resulted in low water loss by deep percolation and it also low evaporation from soil surface, recommending its use in sugarcane cultivation irrigated with TDW. The NI presented water content lower than  pmp to the layers of 0–0.20 and 0.60–0.80 m due to the unavailability of water from irri-

gation or rainfall, since the irrigated treatments at 0.40 m showed levels of moisture below  pmp only to the layer of 0–0.20 m, because water has been applied to deeper soil layers and low capillary rise of moisture in the soil profile. Thus, soil moisture results directly affected the leaf water potential (Fig. 6), and consequently, it also affecting the gas exchange influenced by the distension of the guard cells. As shown in Fig. 3, the low rainfall that influenced the soil moisture (Fig. 4) was also crucial to the lower water potential in leaves to plants non-irrigated at 110 and 160 DAH on the two times that the readings were taken (5 a.m. and 12 p.m.), and these results probably continued for almost the entire growing season due to low rainfall. Among the irrigated plots there were no significant differences. The results of chlorophyll a, chlorophyll b, and total (a + b) are presented in Table 2. The largest significant differences were observed among treatments after the 155 DAH, which likely was caused by low rainfall and high water demand in this crop development stage due to the fast stems growth. As occurred to the leaf water potential, no significant differences were observed among the irrigated treatments, there was lower pigments concentration only when compared to the NI (Table 3). Chlorophyll measurement for being quick and easy to perform, it can help in the diagnosis of water stress on nonirrigated crops, in which these plots reached FCIa average values equal to 26.88, exactly during the period of low rainfall while S20 reached maximum FCIa value of 36.18 to 83 DAH when the plants were still young and without stems. Another point may contribute to the higher chlorophyll content for the irrigated treatments in relation to the NI is the higher leaf nitrogen concentration to irrigated treatments (Table 4), because these nutrients are important components in the formation of pigment in the chloroplasts and were readily available to the plant via SDI, while for the NI was applied in a single topdressing. It can be seen in Table 3, the nitrogen and magnesium concentration were statistically higher for irrigated treatments in relation to the NI. In relation to the standard of Raij et al. (1996), all nutrients were considered suitable for sugarcane. Evaluating varieties tolerant to water stress, Pincelli (2010) observed both chlorophylls a and b for SP81-3250 and RB72454

110

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Fig. 5. Average water content in the soil profile for layers 0–20 m (A), 0.20–0.40 m (B), 0.40–0.60 m (C), 0.60–0.80 m (D) and 0.80–1.0 m (E). NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m.

NI

S20

S40

W20

W40

NI

b

a

a

a

a

b

S20

S40

W20

a

a

a

W40

Ψw (MPa)

0.0 -0.5

a

-1.0 -1.5 -2.0

b

a

a

a

a

a

b

A Ψw5

a

a

a

B

Ψw12

Fig. 6. Leaf water potential at 05:00 a.m. (w5 ) and at 12:00 p.m. (w12 ) to 110 (A) and 160 (B) days after harvesting of the first sugarcane ratoon. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m.

decreased their pigments when exposed to water limitation. This directly affects the photosynthetic rate (Table 5), because the higher chlorophyll concentration provides also the higher absorption and transfer of photosynthetic active radiation (PAR) to the photosynthetic reaction centers. Water stress had an important role in a reduction of leaves pigments slowing its vegetative development, thus reducing also its productivity. In the first three periods analyzed (81, 100, and 113 DAH), few significant differences were also observed among the treatments, mainly due to high rainfall corresponding in this period (from

September/2013 to January/2014) and lower water demand by the crop due the absence of stems in this period. According Doorenbos and Kassam (1979), the critical phase to water stress in sugarcane starts at the beginning of stems growth after the establishment of tillers numbers (crop development) due to high vegetative growth and hence biomass accumulation. From the 140 DAH were noted statistical differences among the treatments in relation to irrigated plots and without irrigation for A and Gs (Table 5). At this stage the water requirements is high (crop coefficient > 1) (Allen, 1998), but the rainfall was very low (only

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Table 2 Falker chlorophyll index a, b and a + b for all treatments during the second sugarcane ratoon. Treatments 83 DAH NI S20 S40 W20 W40 F test 103 DAH NI S20 S40 W20 W40 F test 155 DAH NI S20 S40 W20 W40 F test 183 DAH NI S20 S40 W20 W40 F test 255 DAH NI S20 S40 W20 W40 F test 268 DAH NI S20 S40 W20 W40 F test

FCIa

FCIb

FCI a + b

34.99 ± 2.75 36.18 ± 1.86 34.74 ± 1.53 33.71 ± 2.11 35.18 ± 1.70 1.327ns

12.22 ± 2.25 12.37 ± 1.50 12.92 ± 2.08 11.50 ± 1.55 13.12 ± 1.08 1.363ns

47.21 ± 4.86 48.55 ± 3.33 47.66 ± 3.58 45.21 ± 3.65 48.30 ± 2.78 1.120ns

33.60 ± 0.71 b 34.80 ± 0.68 a 33.59 ± 1.10 b 32.75 ± 0.82 b 33.39 ± 0.31 b 6.054*

12.19 ± 1.16 12.85 ± 0.53 11.89 ± 0.56 11.43 ± 0.78 11.63 ± 0.59 1.861ns

45.79 ± 1.35 b 47.65 ± 1.06 a 45.49 ± 1.66 b 44.19 ± 1.55 b 45.01 ± 0.81 b 4.015*

29.60 ± 1.52 32.23 ± 2.46 31.23 ± 0.74 31.26 ± 1.12 29.37 ± 1.43 3.005ns

8.91 ± 0.59 10.43 ± 1.32 10.10 ± 0.71 9.95 ± 0.56 9.11 ± 0.81 2.879ns

38.51 ± 2.08 b 42.66 ± 3.71 a 41.33 ± 1.36 a 41.21 ± 1.67 a 38.48 ± 2.12 b 3.077*

26.88 ± 1.13 b 33.92 ± 1.47 a 31.94 ± 1.44 a 31.59 ± 2.02 a 33.22 ± 0.65 a 17.143*

7.98 ± 0.80 b 12.31 ± 1.55 a 11.05 ± 1.97 a 10.88 ± 0.65 a 11.07 ± 0.41 a 12.155*

34.86 ± 1.91 b 46.23 ± 1.87 a 42.99 ± 3.35 a 42.47 ± 2.61 a 44.29 ± 0.95 a 16.511*

27.64 ± 2.77 b 32.66 ± 2.20 a 32.74 ± 1.17 a 31.40 ± 0.89 a 31.28 ± 1.06 a 6.031*

8.02 ± 1.23 b 10.72 ± 1.17 a 10.86 ± 1.09 a 10.58 ± 0.77 a 10.62 ± 0.68 a 7.792*

35.66 ± 3.65 b 43.38 ± 3.35 a 43.60 ± 2.04 a 41.98 ± 1.65 a 41.90 ± 1.72 a 7.582*

28.64 ± 1.07 a 33.44 ± 1.44 b 33.46 ± 2.23 b 32.96 ± 3.43 b 32.74 ± 0.73 b 4.219*

8.92 ± 0.27 a 11.62 ± 1.19 b 12.80 ± 1.57 b 11.52 ± 1.94 b 11.76 ± 0.78 b 5.664*

37.56 ± 1.11 b 45.06 ± 2.61 a 46.26 ± 3.75 a 44.48 ± 5.30 a 44.50 ± 0.80 a 5.688*

NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. FCIa: Falker chlorophyll index a; FCIb: Falker chlorophyll index b; FCIa + b: Falker chlorophyll index a + b;DAH: days after harvest. * F test significant at P ≤ 0.05. ns F test non-significant at P ≤ 0.05. Table 3 Average leaf concentration of macronutrient and sodium in January/2014 g kg−1 for second sugarcane ratoon. Treatments

Nitrogen

Phosphorus

Potassium

Calcium

Magnesium

Sodium

NI S20 S40 W20 W40 F test Raij et al. (1996)

20.1 ± 0.03 b 20.9 ± 0.08 a 20.6 ± 0.01 a 20.9 ± 0.03 a 21.1 ± 0.03 a 8.548* 18–25

2.00 ± 0.01 a 1.94 ± 0.01 a 1.92 ± 0.01 a 2.04 ± 0.01 a 2.06 ± 0.01 a 1.420ns 1.5–3.0

12.1 ± 0.11 a 11.8 ± 0.06 a 12.3 ± 0.06 a 12.0 ± 0.06 a 13.1 ± 0.08 b 3.168* 10–16

5.72 ± 0.04 a 6.22 ± 0.07 a 6.12 ± 0.04 a 5.76 ± 0.03 a 6.08 ± 0.06 a 0.856ns 2–8

2.13 ± 0.01 b 2.46 ± 0.01 a 2.48 ± 0.01 a 2.46 ± 0.02 a 2.47 ± 0.01 a 132.667* 1–3

36.6 ± 5.6 a 37.0 ± 8.3 a 38.2 ± 6.4 a 35.8 ± 7.1 a 41.4 ± 6.9 a 0.440ns –

NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. * F test significant at P ≤ 0.05. ns F test non-significant at P ≤ 0.05.

12 mm in February), there was a reduction in gas exchange rate on the NI because the lower turgor pressure of the guard cells results also in lower stomatal conductance, reducing the CO2 input to the photosynthetic process (Taiz and Zeiger, 2013). The fast vegetative growth phase (from the 120 DAH), where there is fast growing of stems and leaf expansion, it was the period in which the plants more water required for the process of gas exchange with the atmosphere. Thus, the availability of water in the soil negatively affects the sugar yield (Pires et al.,

2013). This effect was observed during the measurements, and to 260 DAH the photosynthetic rate for the NI reached the lowest value (11.10 ␮mol m−2 s−1 ), this rate corresponds less than 50% of the average by the irrigated treatments, because in this period was observed a precipitation around 30 mm to the months of May and June. Even though transpiration has been significantly reduced to NI, its WUE was statistically lower also because photosynthesis was greatly reduced affecting the ratio A/E (Table 5).

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Table 4 Photosynthesis (A), transpiration (E), stomatal conductance (Gs), water use efficiency (WUE) and intercellular carbon (C) during the second sugarcane ratoon. Treatments 81 DAH NI S20 S40 W20 W40 F test 100 DAH NI S20 S40 W20 W40 F test 113 DAH NI S20 S40 W20 W40 F test 140 DAH NI S20 S40 W20 W40 F test 163 DAH NI S20 S40 W20 W40 F test 169 DAH NI S20 S40 W20 W40 F test 225 DAH NI S20 S40 W20 W40 F test 260 DAH NI S20 S40 W20 W40 F test

Ci ␮mol CO2 mol−1

E mmol H2 O m−2 s−1

Gs mol m−2 s−1

A ␮mol m−2 s−1

WUE –

183.50 ± 8.06 180.25 ± 9.87 187.75 ± 12.5 183.75 ± 7.18 169.50 ± 5.91 1.999ns

6.66 ± 0.45 a 7.27 ± 0.19 a 6.66 ± 0.36 a 5.45 ± 0.50 b 7.32 ± 0.42 a 12.764*

0.50 ± 0.10 0.61 ± 0.04 0.54 ± 0.02 0.59 ± 0.04 0.57 ± 0.06 1.934ns

27.49 ± 1.81 b 32.95 ± 1.11 a 33.62 ± 4.43 a 31.02 ± 2.48 a 33.85 ± 1.53 a 3.979*

4.13 ± 0.03 c 4.53 ± 0.13 c 5.05 ± 0.54 b 5.71 ± 0.36 a 4.63 ± 0.10 c 19.590*

150.25 ± 8.99 b 135.25 ± 12.8 b 173.50 ± 13.9 a 178.75 ± 7.45 a 149.75 ± 7.13 b 12.863*

10.83 ± 0.80 a 10.60 ± 0.53 a 10.38 ± 0.21 a 8.37 ± 0.92 b 11.06 ± 0.51 a 15.379*

0.60 ± 0.12 0.63 ± 0.09 0.65 ± 0.09 0.64 ± 0.50 0.65 ± 0.04 0.293ns

35.31 ± 3.77 38.85 ± 1.71 38.30 ± 1.36 34.84 ± 2.34 40.12 ± 3.40 2.491ns

3.26 ± 0.20 b 3.67 ± 0.25 b 3.69 ± 0.21 b 4.20 ± 0.55 a 3.62 ± 0.17 b 5.961*

144.75 ± 6.23 b 142.00 ± 7.57 b 171.75 ± 6.23 a 168.75 ± 5.56 a 159.00 ± 9.20 a 15.779*

9.41 ± 0.75 8.77 ± 0.34 8.95 ± 0.34 8.27 ± 1.26 9.41 ± 0.85 1.369ns

0.63 ± 0.18 0.64 ± 0.04 0.56 ± 0.04 0.63 ± 0.05 0.61 ± 0.04 0.424ns

36.68 ± 3.58 38.56 ± 1.93 38.63 ± 2.05 38.49 ± 2.56 38.79 ± 3.88 0.315ns

3.90 ± 0.22 b 4.41 ± 0.36 a 4.31 ± 0.13 a 4.73 ± 0.74 a 4.12 ± 0.16 b 2.368*

136.75 ± 7.36 b 136.75 ± 9.94 b 154.50 ± 13.1 a 168.75 ± 8.26 a 151.75 ± 12.2 a 5.624*

8.72 ± 1.02 b 10.58 ± 0.65 a 9.74 ± 0.41 a 8.02 ± 1.54 b 9.98 ± 0.36 a 4.274*

0.38 ± 0.14 0.56 ± 0.12 0.55 ± 0.09 0.51 ± 0.02 0.60 ± 0.08 2.827ns

29.12 ± 4.96 36.94 ± 3.51 35.99 ± 5.24 32.16 ± 2.70 38.35 ± 4.73 2.660ns

3.33 ± 0.21 3.49 ± 0.16 3.69 ± 0.45 4.15 ± 0.93 3.84 ± 0.38 1.548ns

127.00 ± 5.94 b 127.33 ± 4.78 b 137.25 ± 1.20 a 146.50 ± 9.88 a 130.25 ± 10.6 b 3.587*

7.57 ± 0.88 b 11.47 ± 0.28 a 11.33 ± 0.39 a 11.00 ± 0.29 a 11.15 ± 0.71 a 32.748*

0.20 ± 0.04 b 0.51 ± 0.02 a 0.59 ± 0.06 a 0.55 ± 0.04 a 0.53 ± 0.08 a 26.802*

20.50 ± 3.22 b 33.72 ± 1.95 a 36.71 ± 2.45 a 34.64 ± 1.95 a 34.58 ± 2.60 a 24.966*

2.70 ± 0.12 c 2.94 ± 0.09 b 3.24 ± 0.13 a 3.15 ± 0.16 a 3.10 ± 0.07 a 9.757*

132.50 ± 7.59 a 133.50 ± 13.5 a 143.75 ± 14.3 a 145.75 ± 9.21 a 141.75 ± 10.7 a 1.167ns

7.11 ± 0.80 b 8.43 ± 0.71 a 8.98 ± 0.18 a 7.87 ± 0.70 a 8.40 ± 0.77 a 6.491*

0.27 ± 0.05 b 0.40 ± 0.010 a 0.47 ± 0.03 a 0.38 ± 0.03 a 0.40 ± 0.08 a 4.756*

23.51 ± 2.93 b 30.39 ± 4.26 a 33.49 ± 1.26 a 30.08 ± 2.32 b 28.99 ± 2.83 a 6.826*

3.31 ± 0.18 3.60 ± 0.30 3.73 ± 0.10 3.83 ± 0.28 3.45 ± 0.09 3.139ns

137.00 ± 13.14 b 118.50 ± 1.29 c 154.50 ± 7.04 a 135.00 ± 5.47 b 152.50 ± 14.4 a 8.689*

5.37 ± 1.14 b 8.67 ± 0.42 a 7.76 ± 0.30 a 7.59 ± 1.22 a 8.07 ± 0.31 a 9.558*

0.15 ± 0.05 b 0.39 ± 0.04 a 0.50 ± 0.08 a 0.44 ± 0.08 a 0.45 ± 0.03 a 20.404*

15.90 ± 3.88 b 31.20 ± 2.56 a 33.10 ± 3.40 a 27.87 ± 3.98 a 29.50 ± 2.31 a 15.156*

2.95 ± 0.21 c 3.59 ± 0.16 b 4.27 ± 0.38 a 3.69 ± 0.37 b 3.66 ± 0.30 b 12.353*

156.25 ± 32.95 161.50 ± 20.27 158.50 ± 10.78 162.50 ± 7.41 162.00 ± 25.2 0.052ns

3.20 ± 0.43 b 5.57 ± 0.57 a 5.68 ± 0.10 a 5.07 ± 0.26 a 6.04 ± 0.44 a 36.786*

0.10 ± 0.02 b 0.33 ± 0.10 a 0.41 ± 0.04 a 0.39 ± 0.07 a 0.34 ± 0.07 a 23.584*

11.10 ± 2.65 b 23.70 ± 2.37 a 27.69 ± 2.05 a 26.09 ± 2.04 a 26.59 ± 4.58 a 37.267*

3.46 ± 0.57 c 4.26 ± 0.19 b 4.88 ± 0.37 a 5.14 ± 0.39 a 4.40 ± 0.48 b 6.065*

NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. DAH: days after harvest. * F test significant at P ≤ 0.05. ns F test non-significant at P ≤ 0.05.

Regarding the irrigated treatments, the interaction between water source and the different depths of dripper lines installation, there was no significant differences for gas exchange, probably because all irrigated treatments received enough amounts of water and nutrients to their water and nutrition demands. It is emphasized sugarcane presents C4-carbon fixation, in other words, physiologically presenting a high carboxylation efficiency; therefore, despite the different moisture contents in the soil profile (influenced by different depths installation of dripper lines) and water sources applied, these factors were not enough to influence in different gas exchange among irrigated treatments (Table 4).

Machado et al. (2009) concluded due to low soil water availability, the gas exchange of sugarcane is affected in all its development stages, influenced by the lower leaf water potential, reducing the biomass production by stems and sugar yield. 3.3. Vegetative growth, productivity and technological quality All variables previously had an effect on the vegetative growth of plants, as showed in Table 5. As observed for the physiological parameters, significant differences for the vegetative development began with stems growth

I.Z. Gonc¸alves et al. / Agricultural Water Management 185 (2017) 105–115

113

Table 5 Vegetative growth during the second sugarcane ratoon. Treatments 73 DAH NI S20 S40 W20 W40 F test 112 DAH NI S20 S40 W20 W40 F test 136 DAH NI S20 S40 W20 W40 F test 171 DAH NI S20 S40 W20 W40 F test 201 DAH NI S20 S40 W20 W40 F test 261 DAH NI S20 S40 W20 W40 F test 281 DAH NI S20 S40 W20 W40 F test

Tiller N m−1

Leaf area m2

Leaf area index –

Plant height m

Stem volume cm3

12.92 ± 2.90 15.92 ± 1.42 16.33 ± 1.23 13.33 ± 1.77 14.67 ± 3.74 1.764ns

0.05 ± 0.02 0.08 ± 0.04 0.06 ± 0.01 0.08 ± 0.03 0.07 ± 0.01 1.195ns

0.74 ± 0.09 1.49 ± 0.58 1.16 ± 0.24 1.11 ± 0.44 1.07 ± 0.09 1.982ns

0.21 ± 0.01 0.26 ± 0.03 0.21 ± 0.01 0.21 ± 0.03 0.24 ± 0.01 1.659ns

– – – – – –

20.17 ± 2.32 20.83 ± 5.27 19.25 ± 2.63 16.42 ± 1.44 19.42 ± 5.13 0.551ns

0.16 ± 0.06 c 0.26 ± 0.05 a 0.25 ± 0.01 a 0.21 ± 0.01 b 0.25 ± 0.01 a 36.118*

3.50 ± 0.48 6.03 ± 1.50 5.39 ± 0.58 3.88 ± 0.12 5.65 ± 2.27 3.005ns

0.57 ± 0.02 c 0.86 ± 0.02 a 0.77 ± 0.04 b 0.71 ± 0.01 b 0.77 ± 0.04 b 20.045*

– – – – – –

15.25 ± 0.66 16.42 ± 1.42 14.50 ± 3.68 14.00 ± 3.36 15.58 ± 3.57 0.401ns

0.25 ± 0.03 0.44 ± 0.06 0.44 ± 0.08 0.36 ± 0.20 0.41 ± 0.10 3.602ns

4.22 ± 0.84 8.09 ± 1.90 6.94 ± 1.01 5.04 ± 2.44 6.92 ± 0.69 4.117*

1.20 ± 0.21 b 1.54 ± 0.15 a 1.51 ± 0.15 a 1.45 ± 0.19 a 1.48 ± 0.24 a 6.005*

379.43 ± 118 b 743.71 ± 34.3 a 492.56 ± 105 b 433.01 ± 100 b 457.04 ± 128 b 22.580*

9.17 ± 1.84 11.67 ± 2.26 11.08 ± 1.37 9.17 ± 1.50 10.58 ± 1.37 1.489ns

0.37 ± 0.03 b 0.63 ± 0.04 a 0.55 ± 0.02 a 0.59 ± 0.01 a 0.58 ± 0.06 a 33.087*

3.72 ± 0.65 b 8.13 ± 1.52 a 6.73 ± 0.59 a 5.96 ± 0.99 a 6.74 ± 0.55 a 8.447*

1.95 ± 0.10 b 2.51 ± 0.20 a 2.36 ± 0.03 a 2.35 ± 0.15 a 2.33 ± 0.06 a 4.922*

706.65 ± 57.6 b 1203.06 ± 160 a 1098.42 ± 95.0 a 1138.88 ± 23.8 a 978.91 ± 72.6 a 21.421*

6.83 ± 1.62 9.08 ± 1.89 8.50 ± 1.80 7.00 ± 1.39 7.42 ± 1.46 0.939ns

0.43 ± 0.04 b 0.64 ± 0.02 a 0.60 ± 0.02 a 0.56 ± 0.09 a 0.57 ± 0.02 a 6.206*

3.26 ± 0.88 6.46 ± 1.63 5.61 ± 1.04 4.48 ± 1.54 4.67 ± 0.91 2.323ns

2.39 ± 0.23 b 3.16 ± 0.06 a 3.24 ± 0.27 a 2.89 ± 0.18 a 2.92 ± 0.28 a 5.505*

973.46 ± 257 b 1809.89 ± 81.8 a 1652.27 ± 53.2 a 1599.14 ± 218 a 1560.28 ± 214a 7.224*

7.83 ± 1.75 9.75 ± 2.41 8.58 ± 1.52 7.25 ± 0.43 8.50 ± 1.08 1.132ns

0.45 ± b0.0 4 0.64 ± 0.02 a 0.58 ± 0.06 a 0.59 ± 0.02 a 0.59 ± 0.02 a 9.117*

3.87 ± 0.61 b 6.93 ± 1.52 a 5.48 ± 0.61 a 4.74 ± 0.43 a 5.59 ± 0.65 a 6.961*

2.86 ± 0.25 b 3.55 ± 0.20 a 3.62 ± 0.05 a 3.66 ± 0.01 a 3.62 ± 0.09 a 22.248*

1477.33 ± 98.2 b 2245.87 ± 125 a 2220.82 ± 240 a 2231.00 ± 250 a 1921.18 ± 61.3 a 9.579*

6.83 ± 1.66 9.17 ± 2.55 8.00 ± 1.39 6.83 ± 0.38 8.08 ± 1.04 1.295ns

0.31 ± 0.07 b 0.56 ± 0.01 a 0.59 ± 0.03 a 0.54 ± 0.04 a 0.55 ± 0.04 a 23.112*

2.43 ± 1.04 b 5.69 ± 1.47 a 5.29 ± 1.01 a 4.09 ± 0.60 a 4.92 ± 0.59 a 7.225*

2.90 ± 0.03 b 3.63 ± 0.22 a 3.60 ± 0.15 a 3.67 ± 0.07 a 3.61 ± 0.06 a 16.770*

1585.51 ± 213 b 2612.64 ± 693 a 2587.92 ± 97.6 a 2332.26 ± 264 a 2375.64 ± 249 a 3.685*

NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, R20: surface water reservoir applied to 0.20 m, R40: surface water reservoir applied to 0.40 m. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. * F test significant at P ≤ 0.05. ns F test non-significant at P ≤ 0.05.

(136 DAH), we also observed higher values to the irrigated treatments for the same reasons presented previously, which directly affected the stems and sucrose yields (Fig. 6). Still in Table 5, a reduction was noted in tillers number over time until its stabilization when the plants accumulate greater leaf area from the beginning of stems development. Thus, there is a greater natural shading on the younger tillers, which limit its developed due the lower PAR absorption to photosynthetic process, resulting in a competition for radiation (Bezuidenhout et al., 2003) accentuated when 70% of the radiation is intercepted by the canopy after at the beginning of the stems development (Inman-Bamber and Smith, 2005), which may be verified by the IAF (Table 5). LA and LAI presented the highest increment until the 171 DAH, occurring stabilization to 261 DAH and then a decrease coming from the competition of plants for space and light (Table 5). However, to NI, for reason of the low rainfall in the period, there was a higher decrease for these parameters to 281 DAH, and it was not

observed stabilization as evident as on the irrigated treatments. Factors such as high temperature under water stress periods causing decrease in leaf area and, according to Inman-Bamber et al. (2005), long time on water stress exposure adversely affects the canopy growth, especially leaf expansion, resulting in an accelerated process of senescence. LA is very important to the light absorption and subsequent development of plants, the higher LA provides also hither PAR uptake to make adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH), subsequent their uses in Calcin Cycle on the light absence makes carbohydrate to plant development (Taiz and Zeiger, 2013). The stem growth stage have been identified as a critical period for water demand (Ramesh, 2000), at this time the damage caused by water stress are more harmful to the production, and in this, studying was observed low volumes precipitated significantly reduced the stems height to the NI from the 136 DAH (Table 6).

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Table 6 Technological quality (%) of sugarcane for all treatments. Attribute

NI

S20

Brix Pol PZA Fiber RS TRS

21.47 16.75 89.98 10.61 0.56 19.57

21.24 21.86 16.09 16.96 87.64 90.69 10.81 11.42 0.63 0.53 16.0 16.75 Within the standard

S40

W20

W40

Average

21.58 16.69 90.01 11.19 0.56 16.51

21.33 16.22 88.33 11.09 0.61 16.10

21.50 >18 19.21 >14 89.33 >85 11.02 from 11 to 13 0.58 <0.8 16.39 >15 Outside of the standard

Consecana (2006)

NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, R20: surface water reservoir applied to 0.20 m, R40: surface water reservoir applied to 0.40 m. Pol: apparent sucrose of the juice; PZA: content of fiber; RS: reducing sugars; TRS: theoretical recoverable sugar.

300

a

Yield (Mg.ha-1)

a a

225

150

a

b

75

a

b

a

a

a

0 NI

S20

S40 Stem

W20

W40

TYRS

Fig. 7. Theoretical yield of recoverable sugar and stem. Médias seguidas por cores iguais não diferem entre si ao nível de 5% de probabilidade pelo teste de Scott Knott. NI: non-irrigated, S20: treated domestic sewage applied to 0.20 m, S40: treated domestic sewage applied to 0.40 m, W20: surface water reservoir applied to 0.20 m, W40: surface water reservoir applied to 0.40 m. Averages followed by the same letter do not differ by the Scott Knott at 5% probability. TYRS: theoretical yield of recoverable sugar.

The productivity and TYRS followed the trending of the values obtained by the vegetative development, where the irrigated treatments were significantly superior to NI (Fig. 7). The irrigated treatments, on average, showed an average yield of stems and TYRS about 75% and 72% higher than NI, being the S20 presenting the greatest differences reaching 95% and 86% with a productivity of 233.69 Mg ha−1 and 37.06 Mg ha−1 for stem and TYRS, respectively. Agreeing with these results, Gava et al. (2011), evaluating the stem yield from three sugarcane varieties (first ratoon) under SDI and fertigation, found statistically higher production to the irrigated treatments, with an average increase of 24% in stems and 23% in sugar compared to NI. In relation to technological quality, the results are shown in Table 6. In general, the sugarcane technological quality was considered appropriate because during the ripening period (interruption of irrigation to 60 days before harvesting) were observed low depth precipitated (total of 25.4 mm) or no precipitation event (last 30 days before harvesting). Only the NI and S20 have the non-standard fiber concentration; however, the values were too close to the considered suitable (11 to 13%) according to Consecana (2006). Quintana et al. (2012) found to SDI provided an increase in productivity by 100.4% (175.1 Mg ha−1 ) and TYRS compared to nonirrigated crops, besides reducing the RS content of the juice. Simões et al. (2015) evaluated the technological quality in three sugarcane seasons in several irrigations systems on the clayey soil, the authors concluded SDI system provided greater than or equal results to other irrigation systems.

development, stem productivity and sugar when compared with cultivation without irrigation. Irrigated treatments with treated domestic wastewater showed the highest absolute values for sugarcane yield, being the S20 presenting the greatest differences reaching 95% and 86% with a productivity of 233.7 Mg ha−1 and 37.1 Mg ha−1 for stem and theoretical yield of recoverable sugar, respectively, still saving water and fertilizers. The two dripper lines installation depths (0.20 or 0.40 m), not influence statistically in different biomass accumulation for the sugarcane among the irrigated treatments independent of the water source applied. However, soil moisture changes according to the installation depth, being higher in the irrigated treatments. The treated domestic wastewater applied through subsurface drip can be used in the sugarcane production; however, it should be done the monitoring of its nutritional quality and sodium content regularly, avoiding excessive application of mineral fertilizers by fertigation.

Acknowledgments This work was supported by the School of Agricultural Engineering of the State University of Campinas; National Counsel of Technological and Scientific Development and the São Paulo Research Foundation for the financial support.

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