Yield and fruit development in mango

agricultural water management 96 (2009) 574–584

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Yield and fruit development in mango (Mangifera indica L. cv. Chok Anan) under different irrigation regimes Wolfram Spreer a,*, Somchai Ongprasert b, Martin Hegele c, Jens N. Wu¨nsche c, Joachim Mu¨ller a a

University of Hohenheim, Institute of Agricultural Engineering, 70593 Stuttgart, Germany Mae Jo University, Department of Soil Science and Conservation, Chiang Mai, Thailand c University of Hohenheim, Institute of Special Crops and Crop Physiology, 70593 Stuttgart, Germany b

article info

abstract

Article history:

‘Chok Anan’ mangoes are mainly produced in the northern part of Thailand for the domestic

Received 19 February 2008

fresh market and small scale processing. It is appreciated for its light to bright yellow color and

Accepted 28 September 2008

its sweet taste. Most of the fruit development of on-season mango fruits takes place during the

Published on line 11 November 2008

dry season and farmers have to irrigate mango trees to ensure high yields and good quality. Meanwhile, climate changes and expanding land use in horticulture have increased the

Keywords:

pressure on water resources. Therefore research aims on the development of crop specific

Deficit irrigation

and water-saving irrigation techniques without detrimentally affecting crop productivity.

RDI

The aim of this study was to assess the response of mango trees to varying amounts of

PRD

available water. Influence of irrigation, rainfall, fruit set, retention rate and alternate bearing

Alternate bearing

were considered as the fruit yield varies considerably during the growing seasons. Yield

Fruit set

response and fruit size distribution were measured and WUE was determined for partial

Fruit drop

rootzone drying (PRD), regulated deficit irrigation (RDI) and irrigated control trees.

Thailand

One hundred ninety-six mango trees were organized in a randomized block design consisting of four repetitive blocks, subdivided into eight fields. Four irrigation treatments have been evaluated with respect to mango yield and fruit quality: (a) control (CO = 100% of ETc), (b) (RDI = 50% of ETc), (c) (PRD = 50% of ETc, applied to alternating sides of the root system) and (d) no irrigation (NI). Over four years, the average yield in the different irrigation treatments was 83.35 kg/tree (CO), 80.16 kg/tree (RDI), 80.85 kg/tree (PRD) and 66.1 kg/tree (NI). Water use efficiency (WUE) calculated as yield per volume of irrigation water was always significantly higher in the deficit irrigation treatments as compared to the control. It turned out that in normal years the yields of the two deficit irrigation treatments (RDI and PRD) do not differ significantly, while in a dry year yield under PRD is higher than under RDI and in a year with early rainfall, RDI yields more than PRD. In all years PRD irrigated mangoes had a bigger average fruit size and a more favorable fruit size distribution. It was concluded that deficit irrigation strategies can save considerable amounts of water without affecting the yield to a large extend, possibly increasing the average fruit weight, apparently without negative long term effects. # 2008 Elsevier B.V. All rights reserved.

* Corresponding author. Present address: Hohenheim Office, 2nd Floor, New Building, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand. Tel.: +66 53 944647; fax: +66 53 893099. E-mail address: [email protected] (W. Spreer). 0378-3774/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2008.09.020


1.

Introduction

Thailand is the most important mango producer of Southeast Asia. Apart from being common tree in house gardens, mango is produced in medium to large plantations all over the country under different agro-ecological conditions. A minor part of it is produced for export to Japan, Singapore, Malaysia and others. The biggest amount is produced for domestic and fresh consumption. This comprises a large variety of local autochthonous species, such as the variety ‘Chok Anan’ which is mainly produced in the northern part of Thailand for the domestic fresh market and small scale processing. It is appreciated for its light to bright yellow color and its sweet taste. In contrast to most mango varieties it has the ability to produce off-season flowering without chemical induction (Chintanawong et al., 2001). Thus, apart from the main harvest in May, two more harvests follow in June and August, generating additional income for farmers and reducing the labor peak at harvest. However, off-season fruiting often has a negative impact on on-season flowering, resulting in alternate bearing. Most of the fruit development of on-season mango fruits takes place during the dry season and farmers have to irrigate mango trees to ensure high yields and good quality. Flower induction takes place in December, when temperatures are low and there is no rainfall (Hegele et al., 2006a). A temperature regime of 25 8C during the day and 15 8C during the night as prevails during this period was found to be the optimum for flower induction (Sukhvibula et al., 1999). Prior to flowering, farmers do not irrigate in order to enhance drought stress to support flower induction. Flowering intensity of mangoes was found to negatively correlate with relative water content (Pongsomboon et al., 1997). Meanwhile, climate changes and expanding land use in horticulture have increased the pressure on water resources. Therefore research aims on the development of crop specific and water-saving irrigation techniques without detrimental effect on crop productivity. So far, there are two methods of deficit irrigation (DI) for saving water in fruit production. One is regulated deficit irrigation (RDI) where a certain percentage of evapotranspiration (ET) is replaced by irrigation applied over the entire rootzone. The other, is partial rootzone drying (PRD) where at each irrigation time only part of the rootsystem is watered while the other side is left to dry, to a predetermined level, before being irrigated next. The root system senses soil drying and produces chemical signals that are transmitted to the shoots to close the stomata (decreasing water loss) and limit vegetative growth, thus improving water use efficiency (WUE) (Dry et al., 1996; Stoll et al., 2000). There is evidence suggesting that the plant hormone abscisic acid (ABA) is a major component involved in the control of stomatal conductance as the soil dries (Davies et al., 2000). ABA reaching the leaves induces partial closure of stomata and improves WUE because photosynthesis is expected to decrease to a lesser extent than does transpiration (Dry and Loveys, 1998). To avoid die off of the roots and in order to induce a new hormonal stimulus, the irrigated and the dry side are normally changed in a 10–14 days cycle (Stoll et al., 2000). The optimal time of alternation is, however, not well investigated (Kang and Zhang, 2004).

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Worldwide, successful attempts have been documented on the use of PRD to improve WUE in vines, various tree crops and horticultural plants. Most studies deal with grapevine, where PRD was first practiced (Dry et al., 1996). Recent studies confirm the applicability of PRD in vines (Chaves et al., 2007; de la Hera et al., 2007). Other perennial plants are apples (Zegbe et al., 2007), pears (Kang et al., 2002), longan (Satienperakul et al., 2006), olives (Wahbi et al., 2005) and raspberries (Grant et al., 2004). The influence on yield and fruit quality is being intensively discussed. It was proposed that PRD has no advantage over RDI, which distributes water evenly over the whole rootzone, with respect to WUE (Gu et al., 2004; Pudney and McCarthy, 2004; Bravdo et al., 2004; Fernandez et al., 2006; Treeby et al., 2007). While plenty of positive reports claim no or minor effects on fruit yield and some even report positive influences on fruit quality (Bussakorn et al., 2001; dos Santos et al., 2003), there are also studies in which detrimental effects on yield have been found (Kirda et al., 2007; O’Connell and Goodwin, 2007). Irrigation requirement of mango is still not well investigated. A progressive crop coefficient (kc) ranging from 0.4 (flowering) to 0.8 (fruit growth) was proposed to calculate crop water requirement (de Azevedo et al., 2003). Studies on the response to deficit irrigation revealed no significant yield decrease under deficit irrigation (Pavel and Villiers, 2004) and no difference in fruit size under conditions of light drought stress between irrigated and non-irrigated trees (Lechaudel et al., 2005). On the other hand a rather high sensitivity to water logging has been reported. CO2 assimilation and stomatal aperture was found to decrease as an immediate response (Zude et al., 1998; Schaffer et al., 2006). In an ongoing study the impact of different irrigation regimes on mango is being investigated. During the first two years the immediate effects on yield and quality parameters have been investigated. It turned out that deficit irrigation has no disadvantageous impact on fruit quality and ripening behavior. The impact on WUE was promising (Spreer et al., 2007a,b). Building up on this experience, the aim of this study was to assess the response of mango trees to varying amounts of water availability over a longer period. Influence of irrigation, rainfall, fruit set, retention rate and alternate bearing were considered as the fruit yield varies considerably amongst growing seasons. Yield response and fruit size distribution were measured and WUE was determined for PRD, RDI, and fully irrigated control trees.

2.

Materials and methods

2.1.

Irrigation treatments

Irrigation experiments were carried out in the years 2004 until 2007, using 196 fourteen-year-old ‘Chok Anan’ mango trees (Mangifera Indica L.), grafted on ‘Talap Nak’ rootstocks, spaced at 4 m 4 m and located at an orchard of Mae Jo University, Chiang Mai, Thailand (18.538N, 100.038E, 350 m a.s.l.). The soil, classified as Regosol according to FAO, is characterized by a high stone content, and thus a low water holding capacity. Water requirement for irrigation was calculated as potential crop evapotranspiration (ETc), based on climatic data

576


Table 1 – Climate data for the three seasons of mango fruit growth 2005–2007 from Mae Jo University Agro meteorological station. Month

Air temperature (8C)

Relative humidity (%) Max.

Pan evap. (mm)

Cloud cover (%)

Sunshine hours

Max.

Min.

Min.

2005 January February March April May

31.00 35.08 35.56 36.80 33.35

13.85 15.22 18.33 20.81 22.51

96.10 94.96 93.45 92.93 93.73

31.68 23.50 28.32 32.43 47.87

2.84 4.05 4.64 5.39 3.91

9.26 1.71 21.29 30.07 62.00

8.41 9.30 8.25 8.19 5.09


30.08 32.75 35.95 35.45 34.17

14.12 16.23 18.55 21.20 21.99

93.42 91.89 90.97 91.27 91.53

30.94 29.11 26.94 35.40 40.80

2.74 3.68 4.25 4.76 4.84

10.23 15.89 14.35 44.13 45.20

8.66 8.94 8.10 7.63 8.41


30.71 33.04 36.34 36.66 31.11

13.05 14.13 16.63 21.38 22.69

95.29 93.71 92.55 91.30 93.40

27.87 23.89 21.74 32.33 58.33

3.03 3.61 4.05 5.54 4.54

16.88 15.39 8.84 32.53 84.93

7.96 8.70 8.01 8.06 3.39

obtained from the meteorological station of Mae Jo University (Table 1), using CROPWAT computer code to calculate reference evapotranspiration (ET0) based on the Penman– Monteith equation (Allen et al., 1998). A crop coefficient (kc) of 0.8 was used for the calculation. Rainfall was measured on the field using a standardized container with daily manual readings. The amount of rain was taken into account and irrigation paused or reduced accordingly. The trees were organized in a randomized block design consisting of four repetitive blocks, subdivided into eight fields. Four irrigation treatments have been evaluated with respect to mango yield and fruit quality: (a) control, CO = 100% of ETc, (b) RDI = 50% of ETc, (c) PRD = 50% of ETc, applied to alternating sides of the root system and (d) no irrigation (NI). In 2004, 2006 and 2007 CO and RDI were irrigated with NETAFIM Supernet 50 micro-sprinklers, with a flow rate of 50 l/h and a wetted diameter of 3.0 m, PRD was irrigated with six NETAFIM JR8 drippers (flow rate 8 l/h) mounted on two lines on both sides of the tree trunk. Alternately one line with three drippers was opened. In 2005, PRD was irrigated with micro-sprinklers and RDI with drippers in order exclude the influence of the different irrigation systems. As no difference was detected the treatments were switched back, as microsprinklers are more widespread among Thai fruit farmers, while drippers enable an easy switching of the sides and are thus appropriate for establishing PRD. The specific costs per tree of both methods were found to be on an equal level (Spreer and Ko¨ller, 2005). As all emitters are pressure compensated, uniform irrigation was guaranteed on the gently sloping experimental field. Total water applied was measured by use of a flow meter in the main line. Water applied per tree was calculated based on application time and nominal flow rate (Fig. 1). In the PRD treatment changing between the irrigated and dry sides took place every 2 weeks in 2004, 2006 and

2007. This interval was chosen following previously published studies (e. g. Stoll et al., 2000). In 2005 irrigated sides should have been changed at the occurrence of drought stress. However, stomatal aperture as drought stress indicator did not decrease due to early rainfall which interfered in the drying circle of the PRD treatment. Thus changing took place only once at two prior to harvest. Soil moisture was monitored by use of time domain reflectometry (TDR). TDR probes were built at Hohenheim University, the read out device was a Tektronix 1502 B cable tester (Tektronix, Beaverton, USA). In each treatment two probes were installed in the rootzone at a depth of 15 and 50 cm, respectively. In the PRD treatment two probes were installed on both sides of the tree.

2.2.

Yield measurements and evaluation

At harvest, yield was determined separately for each tree in all treatments by the use of a mechanical balance. All fruits were counted and classified according to weight classes, as recommended by the Ministry of Agriculture of Thailand. The classification scheme, together with the yields and size distribution of 2004 and 2005 has been published earlier (Spreer et al., 2007a). Alternate bearing was analyzed for the mango growing season from 2004 to 2007. It was considered a change in yield due to alternate bearing if more than 75% of the yield in two seasons was obtained in one season. If the yield was higher as in the previous year it was classified as yield increase, when it was lower, it was classified as decrease. If in both years more than 25% of the yield of the two seasons was obtained, it was considered as no alternation. WUE was calculated per tree as the harvested yield (kg) per irrigation water (m3) according to FAO recommendations (Doorenbos and Kassam, 1979).


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Fig. 1 – Irrigation, rain and soil moisture at Ban Bong mango orchard during the mango growing seasons 2005 (A), 2006 (B) and 2007 (C). Irrigation and rainfall data are the sum of 10 days in the treatments control (irriCO), partial rootzone drying (irriPRD) and regulated deficit irrigation (irriRDI). Soil moisture data have been interpolated in a 10 days interval for CO (moistCO), RDI (moistRDI) and two sides of the PRD treatment (moistPRDl and moistPRDr).

2.3.

Fruit drop, fruit set and retention rate

In 2007 starting from the 3rd day after full bloom (DAFB) all dropped fruits under all trees in the experiment were collected, counted and weighed. Fruit drop was recorded weekly in number and weight. After harvest the number of all dropped fruits per tree and all harvested fruit were added up to estimate the total fruit set. The retention rate was calculated as the percentage of fruits attached to the tree at harvest as compared to the calculated initial fruit set.

2.4.

Fruit growth assessment

Starting from March the fruit growth was assessed on the tree by means of a mechanical vernier caliper. Three dimensions

were measured: fruit length, biggest fruit width and biggest fruit thickness. From those data the fruit mass was calculated following an equation for mass: size correlation. In 2005 only two (NI and RDI) and four (PRD and CO) fruits, respectively, have been randomly selected and measured at 51, 66, 85, 93 DAFB on the tree, and after harvest (at 100 DAFB) in the laboratory. In 2006, 10 fruits per treatment with a uniform size and shape have been selected on the 30th DAFB and measured in one-week intervals until harvest (98 DAFB). In 2007, four branches per treatment were randomly selected and all fruits were measured 43, 51, 61, 65, 71, 78, 85 and 92 DAFB and at harvest (98 DAFB). The leaf area of all branches was determined at harvest in order to compare the fruit growth with respect to the photosynthetic active leaf surface.

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Table 2 – Irrigation and harvest data of three cropping seasons, 2005–2007. n

Yield (kg/tree)

Irrigation (m3/tree)

Rain in season (mm)

WUE (kg/m3)

Fruits/tree

Fruit weight (g)

Number of fruits according to size classesa >500

401–500

301–400

251–300

201–250