Plant and Soil 255: 333–341, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
333
Tomato root distribution, yield and fruit quality under subsurface drip irrigation Rui M.A. Machado1,3 , Maria do Ros´ario, G. Oliveira1 & Carlos A. M. Portas2 ´ ´ de Fitotecnia, Universidade de Evora, Apartado 94 7002-554 Evora, Portugal. 2 Instituto Superior de 3 Agronomia, Tapada da Ajuda, 1349-017, Lisboa, Portugal. Corresponding author∗
1 Depart.
Received 3 May 2002; accepted in revised form 18 November 2002
Key words: minirhizotron, processing tomato, root length intensity, subsurface drip irrigation
Abstract Tomato rooting patterns were evaluated in a 2-year field trial where surface drip irrigation (R0) was compared with subsurface drip irrigation at 20 cm (RI) and 40 cm (RII) depths. Pot-transplanted plants of two processing tomato, ‘Brigade’ (C1) and ‘H3044’ (C2), were used. The behaviour of the root system in response to different irrigation treatments was evaluated through minirhizotrons installed between two plants, in proximity of the plant row. Root length intensity (La ), length of root per unit of minirhizotron surface area (cm cm−2 ) was measured at blooming stage and at harvest. For all sampling dates the depth of the drip irrigation tube, the cultivar and the interaction between treatments did not significantly influence La . However differences between irrigation treatments were observed as root distribution along the soil profile and a large concentration of roots at the depth of the irrigation tubes was found. For both surface and subsurface drip irrigation and for both cultivars most of the root system was concentrated in the top 40 cm of the soil profile, where root length density ranged between 0.5 and 1.5 cm cm−3 . Commercial yields (t ha−1 ) were 87.6 and 114.2 (R0), 107.5 and 128.1 (RI), 105.0 and 124.8 (RII), for 1997 and 1998, respectively. Differences between the 2 years may be attributed to different climatic conditions. In the second year, although no significant differences were found among treatments, slightly higher values were observed with irrigation tubes at 20 cm depth. Fruit quality was not significantly affected by treatments or by the interaction between irrigation tube depth and cultivar. Abbreviations: CI – ‘Brigade’; CII – ‘H3044’; DAP – days after planting; La – root length intensity; R0 – surface drip irrigation; RI – irrigation tube at 20 cm depth; RII – irrigation tube at 40 cm depth; Introduction Drip irrigation in processing tomato is a common technique in Portugal due to the Mediterranean climate, with dry and warm summers and high evapotranspiration rates throughout the growing season. These are conditions that make subsurface drip irrigation a suitable alternative to the surface system. With subsurface drip irrigation, evaporation from the topsoil is reduced and water runoff is negligible (Phene, 1991; Phene et al., 1992). In addition, with surface drip irrigation, roots grow preferentially around the emitter area (Oli∗ FAX No: +351-266-711163. E-mail:
[email protected]
veira et al., 1996), which in turn can contribute to improve water availability to the plants when using subsurface drip irrigation. The purpose of the present study was to compare surface vs subsurface drip irrigation (at two different depths) on the root distribution of two processing tomato cultivars. Knowledge of rooting patterns is essential to irrigation and fertiliser management and consequently to tomato yield and quality. Besides using minirhizotrons for root system analysis, trenches were opened perpendicularly to the plant row to examine the root distribution along the soil profile.
334 Table 3. Crop fertilisation (kg ha−1 )
Table 1. Soil physical and chemical characteristics
Sand (%) Silt (%) Clay (%) Bulk density (g cm−3 ) Organic matter (%) pH (H2 O) N (µg g−1 ) P (µg g−1 ) K (µg g−1 ) Ca2+ (cmolc kg−1 ) Mg2+ (cmolc kg−1 )
0–40
Depth (cm) 41–74
92.60 1.70 5.70 1.51 1.09 5.70 3.45 81.84 69.72 0.30 0.18
95.20 2.00 2.80 1.60 0.44 6.20 2.05 73.04 68.06 0.12 0.15
1997
1998
Preplant N P K Ca Mg S
30.0 22.0 172.6 95.9 6.2 38.4
33.3 20.4 141.9 95.8 6.2 33.12
Fertigation N P K Ca
102.0 31.7 216.1 35.1
91.3 26.0 191.7 36.9
75–100 96.00 1.60 2.40 1.64 0.32 6.20 2.18 43.12 78.02 0.11 0.09
Table 2. Monthly rainfall and air temperature during the growing season Temp. (◦ C) Max. Min.
Date
Rainfall (mm)
May June July Aug.
81.0 36.4 18.9 0
1997 22.7 24.4 29.7 25.7
11.7 13.3 15.7 14.9
May June July Aug.
95.6 25.6 0 0
1998 23.5 27.2 31.4 33.0
11.4 13.3 15.0 15.6
Materials and methods Experimental site The experiment was conducted in 1997 and 1998 on a Regosol Soil (Typic Quarzipsamments) at the António Teixeira Research Station, in Coruche, Portugal. Soil characteristics and meteorological data during the experiment are summarised in Tables 1 and 2, respectively. Experimental design and treatments Three drip irrigation depths: (surface (R0), subsurface at 20 cm depth (RI) and subsurface at 40 cm depth
(RII)) and two processing tomato cv, ‘Brigade’ (CI) and ‘H3044’ (CII), were arranged in a split-plot experimental design with four replications. Drip depth was defined as the main factor and the cultivar as the secondary factor. Plot sizes were 1.5 × 10 m2 , each with seven rows. The daily volume of applied water was estimated from ETm (minus rainfall) measured the day before irrigation. When rainfall exceeded the ETm value, irrigation was suspended and the exceeding water was considered in the calculation of the subsequent irrigation volumes. ETm was estimated using the crop coefficient (Kc ) and the Penman Montheith reference evapotranspiration (ETo ) data from a nearby weather station (ETm = Kc ·ETo ). The crop coefficients used in this work were average values established by Doorenbos and Kassam (1986) for the following crop stages: 0.75 for the development stage (from transplanting to beginning of fruit set); 1.15 for the mid-season stage (from the beginning of fruit set to blooming) and 0.88 for the late-season stage (from blooming to fruit ripening, when 75% of the fruits were red or orange). To minimise the effect of different irrigation treatments on plantlets establishment, all plants were sprinkler irrigated at transplanting. Drip irrigation was started 11 days after transplanting and ended when 75% of fruits were red or orange. The total amount of water applied to the crop was 476.0 mm in 1997 and 523.4 mm in 1998. Soil preparation, preceding the installation of the irrigation tubes, consisted of a 40–50 cm deep mouldboard ploughing followed by two 10–15 cm disc
335 harrow operations. Fertilisers were applied (Table 3) before transplanting (in a 15 cm band) directly below the row and by fertigation, starting on the third week after transplanting. Ca (NO3 )2 , KNO3 and H3 PO4, were applied three times per week via fertigation, according to the absorption rates estimated by Phene et al. (1986, 1987). Fertiliser concentrations in the irrigation water and the injection rate were calculated in order to ensure that the electrical conductivity of the water never exceeded 2.5 mS cm−1 . RAM emitters (2.3 l h−1 ) were placed 40 cm apart. Forty-day-old tomato seedlings were transplanted at 20 cm within the row and 150 cm between rows, for a total of 33 333 plants ha−1 . Root measurements Root distribution was estimated at blooming (82 and 75 DAP, for 1997 and 1998 respectively) and harvest (114 and 104 DAP, for 1997 and 1998, respectively) using 1.5 m long minirhizotrons with 5.2 cm diameter. One tube per treatment was installed, parallel to and distant 10 cm from the plant row, between two plants, at an angle of 30 ◦ to the vertical. At 10 cm increments along the tube, roots intersecting the minirhizotron wall were recorded with a 35 mm camera adapted to an endoscope. Root length intensity (La ) was estimated (Tennant, 1975) and converted into root length density (Table 4) using the regressions defined in the calibration procedure described in Machado and Oliveira (2001). For statistical analysis values of root length intensity (cm√ cm−2 ) were transformed using the equation y = (x + 1). This transformation is recommended when zero values are common in the original data set (Underwood, 1981), as in the present study. Crop yield and quality For yield and quality evaluation, all the fruits of plants grown in a 12 m2 area were hand harvested (114 and 104 days after transplanting, in 1997 and 1998, respectively) when approximately 80% of the fruits were red or orange. Fruits were weighed after been sorted into mature, green and rotten sub-groups for commercial yield evaluation. From the mature fruits subset, a sample of 2.5 kg was taken and passed through a 0.8 mm mesh sieve, to separate seeds and epidermis from the juice. Soluble solids (◦ Brix) and pH were measured in the homogenised juice.
Results and discussion Root parameters La data obtained in 1997 and 1998 only for some depths were significantly different respect to the position of the drip irrigation tube, cultivar or interaction between depth of the irrigation tube and cultivar (Tables 5–8). This outcome was probably associated to the high variability of La values, as confirmed by the variation coefficients of the ANOVA, which ranged between 10 and 80%. Great spatial root variability is associated with interaction between root system structure and soil conditions and has been documented by many authors (Brown and Scott, 1984; Hamblin, 1985; Oliveira et al., 2000; Upchurch, 1987; Van Noordwijk, 1993; Zobel, 1991). Variability may also be associated to the method used. Vos and Groenwold (1987) reported a coefficient of variation of 1.5–1.7 times greater for minirhizotrons than for core sampling. However, the minirhizotron method allows a greater number of replications and is less labour-intensive than core sampling. Bar-Yosef et al. (1991), using soil coring, obtained similar results when comparing subsurface versus surface drip irrigation and they also could not find an unequivocal relationship between treatments and root distribution. Despite the lack of significant differences between treatments based on minirhizotron analysis, the distribution of the root system, in relation to the placement of the drip irrigation tube (Figure 1), observed on soil profiles opened perpendicularly to the plant row, show different rooting patterns among irrigation treatments. A large concentration of roots at the depth of the irrigation tubes was found, which is in agreement with the observations reported for tomato under subsurface drip irrigation by Bar-Yosef et al. (1991), for maize by Mitchell (1981) and Phene et al. (1991) and for cotton by Plaut et al. (1996). By using drip irrigation tubes at 40 cm depth (RII) the vertically growing seminal roots quickly reached the moist soil area near the emitter, where a large number of fine roots were found (Figure 1). This result is consistent with the rooting patterns described for processing tomato by Portas (1984), who specifically identified a two-phase response for root growth. In the first phase, vertical growth of seminal roots, with support and reserve functions, occurs. Subsequently (phase II) fine roots (Ø < 1 mm) develop to ensure water and nutrient uptake. The need to insert minirhizotrons at 10 cm from the row, in order not to damage the drip irrigation tubes,
336 Table 4. Relation between root length density (RLD) and root length intensity (La ) (Machado and Oliveira, 2001) Depth (cm)
Equations
n
R2
r
0–40 40–100
RLD = 0.4820 + 0.0113 La – 0.00003 La 2 – 2 × 10−8 La 3 RLD = 0.1874 + 0.0045 La – 0.0002 La 2 + 9.5 ×10−7 La 3
24 36
0.576 0.772
0.76 0.88
Sig. ∗∗ ∗∗∗
(∗∗ , ∗∗∗ Significant at P < 0.01 and 0.001 levels, respectively). Table 5. La at different depths (82 DAP – blooming stage) (1997). data have been transformed
Treat. Depth (R) R0 (Surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) ‘CII (‘H3044’) F (R) F (C) F (R×C)
0 – 10
10 – 20
20 – 30
Depth (cm) 30 – 40 40 – 50
8.11 6.17 4.45
8.49a 6.68b 7.38ab
11.40a 9.30c 10.30b
8.18ab 12.05a 7.56b
4.45 8.03
4.91 10.12
9.66 10.88
0.41NS 9.70NS 1.94NS
12.20∗ 3.21NS 0.67NS
50.31∗∗∗ 0.64NS 1.59NS
50 – 60
60 – 70
70 – 80
12.17a 12.83a 7.81b
3.91 6.75 5.02
4.73 5.84 4.33
2. 10b 3.12ab 2.16b
7.94 10.58
10.72 9.80
5.38 5.07
4.23 5.71
3.27 3.42
11.57∗ 1.83NS 0.42NS
30.95∗∗ 0.09NS 0.16NS
3.93NS 0.05NS 0.22NS
1.59NS 1.55NS 0.26NS
8.59∗ 0.02NS 0.03NS
Within each column means with different letters are significantly different. ∗ , ∗∗ , ∗∗∗ Significant at P < 0.05, 0.01 and 0.001 levels, respectively (LSD). Table 6. La at different depths (75DAP – blooming stage) (1998): data have been transformed
Treat. Depth (R) R0 (Surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) CII (‘H3044’) F (R) F (C) F (R×C)
0 – 10
10 – 20
20 – 30
5.36a 2.67a 1.00b
4.60 3.53 2.35
5.11a 5.68a 1.00b
5.02a 1.00b
5.98a 1.00b
16.41∗ 30.18∗∗ 12.03∗∗
5.31NS 74.61∗∗∗ 5.08NS
Depth (cm) 30 – 40
40 – 50
50 – 60
60 – 70
4.96 7.40 4.09
4.11 4.15 7.46
4.05 6.90 8.69
1.34 5.18 3.39
4.72 3.13
6.48 4.48
5.84 4.64
7.96 5.13
3.89 2.73
30.36∗∗ 1.25NS 1.23NS
1.06NS 1.23NS 1.42NS
4.95NS 0.43NS 0.08NS
1.77NS 4.93NS 2.39NS
3.88NS 0.37NS 0.44NS
Within each column means with different letters are significantly different. ∗ , ∗∗ , ∗∗∗ Significant at P < 0.05, 0.01 and 0.001 levels, respectively (LSD).
could have hidden differences in root system behaviour. At the same time, with subsurface drip irrigation some roots growing along drip irrigation tubes were observed, taking advantage from the lower soil resistance at the soil–tube interface and the water which probably flowed along it.
Root length density (RLD) along the soil profile, estimated from the regression equations defined using the minirhizotron calibration reported in Machado and Oliveira (2001) is displayed in Figures 2 and 3. Data for the interaction between the irrigation treatments and cultivars are only shown when there was a significant effect on RLD. For both surface and sub-
337
Figure 1. Root distribution with subsurface drip irrigation at 20 cm (RI) and 40 cm (RII) depth.
Figure 2. Root length density at blooming stage for different irrigation treatments (Surface – R0, 20 cm - RI, 40 cm - RII, ‘Brigade’- C1, ‘H3044’- CII). (RLD for irrigation × cultivar interaction are only shown when significant).
Figure 3. Root length density at harvest for different irrigation treatments (Surface – R0, 20 cm - RI, 40 cm - RII).
338 Table 7. La at different depths (114 DAP – at harvest) (1997): data have been transformed
Treat. Depth (R) R0 (Surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) CII (‘H3044’) F (R) F (C) F (R×C)
Depth (cm) 40 – 50 50 – 60
0 – 10
10 – 20
20 – 30
30 – 40
60 – 70
70 – 80
80 – 90
90 –100
7.01 7.05 6.45
9.13 7.15 8.96
10.30 9.83 9.55
7.89 9.47 8.99
11.45 8.81 7.59
4.28 4.63 5.57
5.82 4.64 3.44
5.42 4.97 3.84
5.49 4.54 3.80
3.70 6.33 3.42
6.29 7.38
7.55 9.27
10.28 9.50
7.93 9.65
10.76 7.81
4.81 4.85
4.42 4.85
4.62 4.86
4.78 4.44
4.65 4.31
0.06NS 0.32NS 0.36NS
0.62NS 0.80NS 1.54NS
0.08NS 0.17NS 1.05NS
1.84NS 1.26NS 2.97NS
0.98NS 2.08NS 1.94NS
0.36NS 0.01NS 0.24NS
1.99NS 0.15NS 0.25NS
0.72NS 0.04NS 0.99NS
1.27NS 0.09NS 0.41NS
4.36NS 0.06NS 0.58NS
60 – 70
70 – 80
80 – 90
90 – 100
Within each column means with different letters are significantly different (LSD). Table 8. La at different depths (104 DAP – at harvest) (1998): data have been transformed
Treat. Depth (R) R0 (Surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) CII (‘H3044’) F (R) F (C) F (R×C)
Depth (cm) 40 – 50 50 – 60
0 – 10
10 – 20
20 – 30
30 – 40
2.79 4.70 4.84
6.78 3.89 3.37
6.99 5.82 5.72
5.42 6.21 5.44
4.27 3.35 6.74
7.87 3.23 4.61
8.35 7.25 4.74
3.58 2.95 5.74
2.79b 6.61a 8.18a
3.36b 7.04a 7.88a
5.64 2.57
5.90 3.40
8.49a 3.33b
9.49a 1.90b
8.57a 1.00b
6.05 4.38
6.97 6.58
4.66 3.52
7.10a 4.62b
5.91 6.27
2.26NS 2.47NS 2.05NS
3.12NS 5.30NS 3.07NS
0.06NS 28.90∗∗ 0.05NS
0.11NS 20.74∗∗ 1.61NS
2.25NS 27.15∗∗ 1.93NS
4.52NS 2.64NS 10.39∗
2.21NS 0.03NS 2.87NS
0.48NS 2.47NS 4.16NS
7.06∗ 6.63∗ 16.18∗∗
12.80∗ 0.07NS 22.74∗∗
Within each column means with different letters are significantly different. ∗ , ∗∗ Significant at P < 0.05 and 0.01 levels, respectively (LSD).
surface drip irrigation and for both cultivars most of the root system (Figure 2) was concentrated within the top 40 cm of the soil profile where root length density reached 0.5–1.5 cm cm−3 . These results indicate that root growth occurs preferentially in the 0–40-cm soil layer and is independent of the drip irrigation depth used. Similar results have been reported by other authors for processing tomato under surface drip irrigation, using direct sowing (Bar-Yosef, 1977; Bar-Yosef et al., 1980; Maynard et al., 1980; Oliveira et al., 1996; Sanders et al., 1989; West et al., 1979) or transplanted plantlets (Machado et al., 2000).
Crop yield and fruit quality The number of plants per ha was not significantly affected by the treatments or their interaction (Tables 9 and 10). The commercial yield for both years (Tables 9 and 10) was higher using subsurface compared to surface irrigation. Commercial yields (t ha−1 ) were 87.6 and 114.2 (R0), 107.5 and 128.1 (RI), 105.0 and 124.8 (RII) for 1997 and 1998, respectively. Differences between the 2 years can be attributed to different climatic conditions. These results are in agreement with those obtained for tomato by other authors (BarYosef et al., 1991; Davis et al., 1985; El-Gindy and El-Araby, 1996; Hanson et al., 1997; Hutmacher et al., 1985; Phene et al., 1985, 1987). Camp (1998) re-
339 Table 9. Yield, ◦ Brix and pH (1997) Treatment
Plants ha−1
Total yield (t ha−1 )
Commercial yield (t ha−1 )a
◦ Brix
pH
Depth (R) R0 (surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) CII (‘H3044’)
31500 31583 31417
102.72 b 123.91 a 121.83 a
87.59 b 107.50 a 105.00 a
4.29 4.55 4.59
4.07 4.10 4.07
31444 31556
111.71 120.59
95.83 104.23
4.76 4.20
4.06 4.10
F (R) F (C) F (R×C)
0.01NS 0.03NS 0.27NS
7.79∗ 3.57 NS 1.96 NS
5.17∗ 3.78 NS 2.14 NS
0.65NS 4.48NS 0.20NS
0.57NS 2.75NS 0.17NS
◦ Brix
pH
Within each column means with different letters are significantly different. ∗ Significant at P < 0.05 (LSD). a Red and orange fruits. Table 10. Yield, ◦ Brix and pH (1998) Treatment
Plants ha−1
Total yield (t ha−1 )
Commercial yield (t ha−1 )a
Depth (R) R0 (surface) RI (20 cm) RII (40 cm) Cult. (C) CI (‘Brigade’) CII (‘H3044’)
31691 31274 32500
128.12 136.87 133.80
114.16 128.10 124.80
5.36 5.09 5.25
4.38 4.36 4.37
31913 31730
122.74b 143.12a
114.93b 129.76a
5.57 a 4.90 b
4.38 4.36
F (R) F (C) F (R×C)
2.15NS 0.15NS 2.14NS
2.23NS 13.77∗∗ 1.96NS
2.30NS 10.62∗∗ 3.15NS
0.37NS 5.30∗ 0.26NS
0.30NS 1.12NS 0.64NS
Within each column means with different letters are significantly different. ∗ , ∗∗ Significant at P < 0.05 and 0.01 levels, respectively (LSD). a Red and orange fruits.
ported that subsurface drip irrigation may enhance the commercial yield compared to surface drip irrigation. During 1997, with superficial irrigation (R0) the crop often showed a phosphorus deficiency (purple coloration on the leaf undersides) which could have contributed to a lower yield in this year. Geisenberg and Stewart (1986) reported that with low soil temperature phosphorus absorption decreases and only high levels of this nutrient near the root area can meet plant needs. With subsurface drip irrigation phosphorus applied deep in the profile enable the crop to utilise phosphorus more efficiently as it was reported by Phene et al. (1986). These observations have to be tested further applying different amounts of phosphorous.
The irrigation treatments did not significantly affect ◦ Brix and pH of tomato fruits (Tables 9 and 10). This is in agreement with the observations of Davis et al. (1985), Phene et al. (1986, 1987) and BarYosef et al. (1991), for the ◦ Brix and of Davis et al. (1985) for the pH. The tomato juice pH was similar for the two cultivars. For both years the ‘Brigade’ ◦ Brix was higher than ‘H3044’. ◦ Brix values were higher in 1998, which can be attributed to better climatic conditions. According to Grierson and Kader (1986), sugar content is closely correlated with solar radiation during fruit growth. Fruit dry matter content decreases at low temperatures and low radiation levels (Castilla, 1985).
340 Conclusions Results of this 2-year field study indicate that the tomato root system of the two cultivars, at different irrigation depths, had the same behaviour. Roots concentrated preferentially around the emitter area. So, using subsurface drip irrigation systems an accurate management of irrigation and fertilisation is essential to prevent high variations of water and nutrients in the soil which could affect crop yield. At 10 cm from the plant row the depth of the irrigation tube did not affect root length intensity. The results also indicate that subsurface drip irrigation can contribute to increase the commercial production, as occurred during the first year, without affecting fruit quality. The hypothesis of a different crop response to the level of water and phosphorus applied with subsurface drip irrigation has to be tested.
References Bar-Yosef B 1977 Trickle irrigation and fertilization of tomatoes in sand dunes: water, N and P distributions in the soil and uptake by plants. Agron. J. 69, 486–491. Bar-Yosef B, Stammers C and Sagiv B 1980 Growth of trickleirrigated tomato as related to rooting volume and uptake of N and water. Agron. J. 72, 815–822. Bar-Yosef B, Martinez H J J, Sagiv B, Levkovitch I, Markovitch and Phene C J 1991 Processing tomato response to surface and subsurface drip phosphorus fertigation. Bard Project Scientific Report. pp. 175–191. Bet Dagan, Israel. Brown D A and Scott H D 1984 Dependence of crop growth and yield on root development and activity. In Roots, Nutrient and Water Influx and Plant Growth. Eds. S A Barber and D R Bouldin. pp. 101–135. ASA Special Publication 49. Camp C R 1998 Subsurface drip irrigation: a review. Trans. ASAE 41(5), 1353–1367. Castilla N 1995 Manejo del cultivo intensivo con suelo. In El cultivo del tomate. Ed. F Nuez. pp. 190–225. Mundi-Prensa, Madrid. Davis K R, Phene C J, McCormick R L, Hutmacher R B and Meek D W 1985 Trickle frequency and installation depth effects on tomatoes. Proc. Third Int. Drip/Trickle Irrigation Congress. pp. 896–901. Fresno, CA. Doorenbos J and Kassam A H 1986 Yield response to water. FAO, Irrigation and Drainage Paper, 33, Rome. El-Gindy A M and El-Araby A M 1996 Vegetable crops to response to surface and subsurface drip under calcareous soil. Proc. Int. Conf. on Evapotranspiration and Irrigation Scheduling. pp. 1021–1028. St. Joseph. Geisenberg C and Stewart K 1986 Field crop management. In The Tomato Crop. Eds. J G Atherton and J Rudich. pp. 527–592. Chapman and Hall, New York. Grierson D and Kader A A 1986 Fruit ripening and quality. In The Tomato Crop. Eds. J G Atherton and J Rudich. pp. 241–280. Chapman and Hall, New York. Hamblin A 1985 The influence of soil structure on water movement, crop root growth, and water uptake. Adv. Agron. 38, 95–158.
Hanson B R, Schwankl L J, Schulbach K F and Pettygrove G S 1997 A comparison of furrow, surface drip and subsurface drip irrigation on lettuce yield and applied water. Agric. Water Manage. 33 (23), 139–157. Hutmacher R B, Vail S S, Muthamia J G, Mwaja V and Liu R C 1985 Effect of trickle irrigation frequency and installation depth on tomato growth and water status. Proc. Third Int. Drip/Trickle Irrigation Congress. pp. 798–803. Fresno, CA. Machado R M A and Oliveira M R G 2001 The root spatial variability effect on calibration of minirhizotron readings data in processing tomato. Proc. The 6th Symposium of the International Society for Root Research. pp. 538–539. Nagoya, Japan. Machado R M A, Oliveira M R G and Portas C A M 2000 Effect of drip irrigation and fertilization on tomato rooting patterns. Acta Hort. 537, 313–320. Maynard D N, Lorenz O A and Magnifico V 1980 Growth and potassium partitioning in tomato. J. Am. Soc. Hort. Sci. 105, 79–82. Mitchell W H 1981 Subsurface irrigation and fertilization of field corn. Agron. J. 73 (6), 913–916. Oliveira M R G, Calado A M and Portas C A M 1996 Tomato root distribution under drip irrigation. J. Am. Soc. Hort. Sci. 121(4), 644–648 Oliveira M R G, Van Noordwijk M, Gaze S R, Brouwer G, Bona S, Mosca G and Hairiah K 2000 Auger sampling, ingrowth cores and pinboard methods. In Roots Methods: A handbook. Eds. A L Smit, A G Bengough, C Engles, M Van Noordwijk, S Pellerin and S C Van de Geijn. pp. 175–210. Springer, New York. Phene C J 1991 Advances in irrigation under water shortage conditions. Proc. Conference on Collaborative Research and Development Applications in Arid Lands. pp. 93–110. Santa Barbara, California. Phene C J, Bar-Yosef B, Hutmacher R B, Patton S H, Davis K R and McCormick R L 1986 Fertilization of high yielding subsurface trickle irrigated tomatoes. Proc. 34th Annual California Fertilizer Conference. pp. 33–43. Fresno, CA. Phene C J, Davis K R, Hutmacher R B and McCormick R L 1987 Advantages of subsurface irrigation for processing tomatoes. Acta Hort. 200, 101–113. Phene C J, Davis K R, Hutmacher R B, Bar-Yosef B, Meek D W and Misaki J 1991 Effect of high frequency surface and subsurface drip irrigation on root distribution of sweet corn. Irrigation Sci. 12 (2), 135–140. Phene C J, Hutmacher R B, Ayars J E, Davis K R, Mead R M and Schoneman R A 1992 Maximizing water use efficiency with subsurface drip irrigation. International Summer Meeting, Charlotte, 20 p. Phene C J, McCormick R L, Miyamoto J M, Meek D W and Davis K R 1985 Evapotranspiration and crop coefficient of trickle irrigated tomatoes. Proc. Third Int. Drip/Trickle Irrigation Congress. pp. 823–831. Fresno, CA. Plaut Z, Carmi A and Grava A 1996 Cotton root and shoot responses to subsurface drip irrigation and partial wetting of the upper soil profile. Irrigation Sci. 16 (3), 107–113. Portas C A M 1984 Estudos del sistema radical de cultivos horticolas. XXIV Congresso Brasileiro e I Reunião Latino-Americana de Olericultura F.C.A.V. pp. 16–50. Jabotical, Brasil. Sanders D C, Howell T A, Hile M M S, Hodges L and Phene C J 1989 Tomato root development affected by travelling trickle irrigation rate. HortScience 24(6), 930–933. Silva W L C, Giordano B, Marqueli W A, Fontes R R and Gornat B 1998 Response of six processing tomato cultivars to subsurface drip fertigation. Acta Hort. 487, 569–573.
341 Tennant D 1975 A test of a modified line intersect method of estimating root length. J. Ecology. 63, 995–1001. Underwood A J 1981 Techniques of analysis of variance in experimental marine biology and ecology. Oceonagr. Mar. Biol. Ann. Ver. 19, 513–605. Upchurch D R 1987 Conversion of minirhizotron-root intersections to root length density. In Minirhizotron Observation Tubes: Methods and Applications for Measuring Rhizosphere Dynamics. Ed. H M Taylor. pp. 51–65. ASA Special Publication 50. Van Noordwijk M 1993 Roots: length, biomass, production and mortality. Methods for root research. In Tropical Soil and Biology and Fertility, a handbook of methods. Eds. J M Anderson and J S I Ingram. pp. 132–144. CAB International, Wallingford.
Vos J and Groenwold J 1987 The relation between root growth along observation tubes and in bulk soil. In Minirhizotron Observation Tubes: Methods and Applications for Measuring Rhizosphere Dynamics. Ed. H M Taylor. pp. 39–49. ASA Special Publication 50. West D W, Merrigan I F, Jaylor J A and Collins G M 1979 Salinity gradients and growth of tomato plants under drip irrigation. Soil Sci. 127(5), 281–291. Zobel W R 1991 Genetic control of root systems. In Plant Root Systems. The hidden half. Eds. Y Waisel, A Eshel and U Kafkafi. pp. 27–33. New York.
