Influence of Soil Moisture on Yield and Quality of Tomato on a Heavy Clay Soil

The effect of three soil moistnre regimes [deficit: 22-26mm H20 per 100 mm soil depth, field capacity (FC): 34-43 mm and saturation: 44-48 mm] on growth, yield and quality of a tomato (Lyeopersieon eseulen/um L. Mill) cultivar 'Improved Apollo' was examined on a heavy clay soil. Leaf area and plant height were reduced in deficit and saturation, whereas stem diameter increased with increasing soil moisture. Fruit yield declined hy 31 and 24% in deficit and saturation respectively compared with the FC. Maximum attainable fruit yield would be achieved with 35 mm H20 per 100 mm soil depth. Total titratable acidity (TTA), ascorbic acid (AA) and firmness decreased and pH increased with increasing soil moisture. Dry matter, total soluble solids (TSS), TSS: TTA and blossom end rot (BER) were highest for deficit, followed by saturation and lowest at FC. Although yield increased and BER decreased at FC, other quality improved with water stress compared to FC. INTRODUCTION Tomato is precise in terms of its water requirements (Rudich and Luchinsky, 1986). With moisture in excess of plant requirements, water replaces air in the soil and reduces mobility of oxygen that remains trapped in air pockets or dissolved in the soil water (Meek et aI., 1983). By decreasing the supply of soil oxygen to tomato roots, high soil moisture can cause large losses in crop yield and quality (Poysa et aI., 1987). Deficit irrigation enhances fruit quality. However, dry soil constrains growth and development and exacerbates physiological disorders (Guichard et aI., 2001). Drought causes only small reductions in yield and quality if imposed after flowering and fruit set (Grierson and Kader, 1986). Heavy irrigation during the period of fruit development and maturation has adverse effects on quality indices as shown by negative linear correlations between water consumption on one hand and total soluble solids (TSS) and total titratable acidity (TTA) on the other resulting in a negative correlation between crop yield and quality (Rudich and Luchinky, 1986), which is largely variety specific. We examined the effect of irrigation rates on growth, yield and quality of tomato Cv:']mprovedApollo'. MATERIALS AND METHODS The crop was sown on 5 May 2003, in black sealed plastic containers (25 cm diameter x 28 cm height) filled with 18.3 kg of black heavy clay (voertisoV soil in&ide the screen house (67% of full sunlight) at Rockhampton, Australia (23 22' Sand 150 31' E). The field capacity (FC) and wilting coefficient of the soil was 43 and 22 mm H20 per 100 mm soil depth respectively. The experiment was laid out in a randomised complete block design. Three irrigation levels (Deficit: 22-26 mm H20 per 100 mm soil depth (50-60% of FC,); FC: (34-43 mm) and Saturated (43-48 mm» replicated five times .. Each plot consisted of a fully bordered container, spaced at 75 cm x 60 cm, planted WIth a smgle plant pruned to a single stem and staked. Soil moisture was determined by a Microgopher (a time domain refractometry technique from Soil Moisture Technology, Australia) and gravimetric determination by weighing pots twice daily (8 am & 2 pm). Plant height, leaf area and stem dIameter were recorded on each plant at 15-day intervals. As fresh fruit were harvested from 134 to 159 days after sowing, fruit samples were dried, and total dry matter (OM) was determined. Proe. IS on Hart. in Asian-Pacific Region Ed. R. Drew Acta Hart. 694, ISHS 2005 451 Fruit OM, TSS, TTA, pH, firmness, ascorbic acid (AA) and blossom end rot (BER) were assessed on uniformly ripe fruit as described by Grierson and Kader (1986). Data were subjected to analysis of variance (ANOVA) using generalized linear model of SYSTAT 9 (SPSS Inc, 1999). F-test was significant at p ::: 0.05. Regressions from individual plot data were used to determine soil moisture and yield relationship. RESULTS AND DISCUSSION Weather, Soil Moisture and Water Use Soil moisture over the period remained at 22-26,34-43 and 43-48 nun/IOO rnrn for deficit, FC and saturation respectively. Actual amounts of water applied over the season were 188.4 L, 134.9 Land 100.7 L planrl, for FC, saturation and deficit treatments, respectively. Mean temperatures ranged between 11 and 24'C with a growing season mean of 18.1 'C. Soil and ambient temperatures declined gradually for the first 3 months, followed by a steady increase. Daily solar radiation ranged from 1.2-16.55 MJ m· with a season average of 10.36 MJ m· day·l and a growing season total of 1545 MJ m· Daily solar radiation declined, as for temperature, gradually for the first three months followed by a steady increase for rest of the crop period (data not presented). Plant Growth and Development Characteristics Leaf area was reduced by 35 and 44% in deficit and saturation respectively, compared with that of the FC whereas plants were significantly taller at FC, intermediate in saturation and shortest for the deficit treatment. Li et al. (1999) also observed retardation of tomato growth due to soil moisture stress. Stem diameter at harvest increased significantly with increasing soil moisture content (Table I). Frnit Yield, Yield Components and Dry Matter Partitioning Yield decreased by 31 and 24% respectively in deficit and saturation compared with Fe. The highest yield in FC was attributable to heavier fruits (Table I). An extrapolated highest yield at 35 mm irrigation suggested that the crop could be maintained at less than FC for highest yield (Fig. I). OM partitioning was proportionately lower to stem (9.8 and 13.5 vs 22.6%), higher to leaf (22.5 and 22.1 vs 20.6%), and fruits (62.8 and 62.9 vs 58.6%) in deficit and saturation compared to FC respectively. However, partitioning to root was higher (1.8 vs 1.03 and 1.1 %) for deficit compared to saturation and FC (Fig. 2). The harvest index (HI), measured as dry fruit weight to total dry weight was higher for deficit (0.637) and saturation (0.633) compared with the FC (0.593). This results is in agreement with Martin et al. (2003) work in clover but such an effect was not evident when irrigation was reduced from satisfying full to 66% and 33% of the canopy transpirational demand in maize (Paolo et aI., 2001). . Fruit Quality and Blossom End Rot Fruit OM % was significantly greater in the deficit, followed by saturation and FC. Fruit yield and OM were, therefore, negatively correlated as reported by Renquist and Reid (2001). Fruit firmness and TSS were significantly higher at deficit compared with FC and saturation. The TTA and AA decreased and pH increased with increasing soil moisture (Table I). However, the ratio of TSS: TTA was highest at deficit, followed by saturation and lowest in FC. That moisture stress increased TSS:TTA ratio was also noted by Elkner and Kaniszewski (1995). BER increased by three fold in deficit and saturation compared with FC (Table I). Soil moisture stress in association with low air humidity probably reduced the availability of Ca+ in the tomato fruits, resulting in increased BER. CONCLUSIONS Soil moisture beyond 35 mm reduced fruit yields suggesting that irrigation below FC maximize yield. Soil moisture stress improved eating quality but increased BER. An


INTRODUCTION
Tomato is precise in terms of its water requirements (Rudich and Luchinsky, 1986).With moisture in excess of plant requirements, water replaces air in the soil and reduces mobility of oxygen that remains trapped in air pockets or dissolved in the soil water (Meek et aI., 1983).By decreasing the supply of soil oxygen to tomato roots, high soil moisture can cause large losses in crop yield and quality (Poysa et aI., 1987).
Deficit irrigation enhances fruit quality.However, dry soil constrains growth and development and exacerbates physiological disorders (Guichard et aI., 2001).Drought causes only small reductions in yield and quality if imposed after flowering and fruit set (Grierson and Kader, 1986).
Heavy irrigation during the period of fruit development and maturation has adverse effects on quality indices as shown by negative linear correlations between water consumption on one hand and total soluble solids (TSS) and total titratable acidity (TTA) on the other resulting in a negative correlation between crop yield and quality (Rudich and Luchinky, 1986), which is largely variety specific.We examined the effect of irrigation rates on growth, yield and quality of tomato Cv:']mprovedApollo'.

MATERIALS AND METHODS
The crop was sown on 5 May 2003, in black sealed plastic containers (25 cm diameter x 28 cm height) filled with 18.3 kg of black heavy clay (voertisoV soil in&ide the screen house (67% of full sunlight) at Rockhampton, Australia (23 22' Sand 150 31' E).The field capacity (FC) and wilting coefficient of the soil was 43 and 22 mm H20 per 100 mm soil depth respectively.The experiment was laid out in a randomised complete block design.Three irrigation levels (Deficit: 22-26 mm H 2 0 per 100 mm soil depth (50-60% of FC,); FC: (34-43 mm) and Saturated (43-48 mm» replicated five times .. Each plot consisted of a fully bordered container, spaced at 75 cm x 60 cm, planted WIth a smgle plant pruned to a single stem and staked. Soil moisture was determined by a Microgopher (a time domain refractometry technique from Soil Moisture Technology, Australia) and gravimetric determination by weighing pots twice daily (8 am & 2 pm).Plant height, leaf area and stem dIameter were recorded on each plant at 15-day intervals.As fresh fruit were harvested from 134 to 159 days after sowing, fruit samples were dried, and total dry matter (OM) was determined.
Fruit OM, TSS, TTA, pH, firmness, ascorbic acid (AA) and blossom end rot (BER) were assessed on uniformly ripe fruit as described by Grierson and Kader (1986).
Data were subjected to analysis of variance (ANOVA) using generalized linear model of SYSTAT 9 (SPSS Inc, 1999).F-test was significant at p ::: 0.05.Regressions from individual plot data were used to determine soil moisture and yield relationship.

RESULTS AND DISCUSSION
Weather, Soil Moisture and Water Use Soil moisture over the period remained at 22-26,34-43 and 43-48 nun/IOO rnrn for deficit, FC and saturation respectively.Actual amounts of water applied over the season were 188.4 L, 134.9 Land 100.7 L planrl, for FC, saturation and deficit treatments, respectively.Mean temperatures ranged between 11 and 24'C with a growing season mean of 18.1 'C.Soil and ambient temperatures declined gradually for the first 3 months, followed by a steady increase.Daily solar radiation ranged from 1.2-16.55MJ m• 2 with a season average of 10.36 MJ m• 2 day•l and a growing season total of 1545 MJ m• 2 Daily solar radiation declined, as for temperature, gradually for the first three months followed by a steady increase for rest of the crop period (data not presented).

Plant Growth and Development Characteristics
Leaf area was reduced by 35 and 44% in deficit and saturation respectively, compared with that of the FC whereas plants were significantly taller at FC, intermediate in saturation and shortest for the deficit treatment.Li et al. (1999) also observed retardation of tomato growth due to soil moisture stress.Stem diameter at harvest increased significantly with increasing soil moisture content (Table I).

Frnit Yield, Yield Components and Dry Matter Partitioning
Yield decreased by 31 and 24% respectively in deficit and saturation compared with Fe.The highest yield in FC was attributable to heavier fruits (Table I).An extrapolated highest yield at 35 mm irrigation suggested that the crop could be maintained at less than FC for highest yield (Fig. I).OM partitioning was proportionately lower to stem (9.8 and 13.5 vs 22.6%), higher to leaf (22.5 and 22.1 vs 20.6%), and fruits (62.8 and 62.9 vs 58.6%) in deficit and saturation compared to FC respectively.However, partitioning to root was higher (1.8 vs 1.03 and 1.1 %) for deficit compared to saturation and FC (Fig. 2).The harvest index (HI), measured as dry fruit weight to total dry weight was higher for deficit (0.637) and saturation (0.633) compared with the FC (0.593).This results is in agreement with Martin et al. (2003) work in clover but such an effect was not evident when irrigation was reduced from satisfying full to 66% and 33% of the canopy transpirational demand in maize (Paolo et aI., 2001). .
Fruit Quality and Blossom End Rot Fruit OM % was significantly greater in the deficit, followed by saturation and FC.Fruit yield and OM were, therefore, negatively correlated as reported by Renquist and Reid (2001).Fruit firmness and TSS were significantly higher at deficit compared with FC and saturation.The TTA and AA decreased and pH increased with increasing soil moisture (Table I).However, the ratio of TSS: TTA was highest at deficit, followed by saturation and lowest in FC.That moisture stress increased TSS:TTA ratio was also noted by Elkner and Kaniszewski (1995).BER increased by three fold in deficit and saturation compared with FC (Table I).Soil moisture stress in association with low air humidity probably reduced the availability of Ca 2 + in the tomato fruits, resulting in increased BER.

CONCLUSIONS
Soil moisture beyond 35 mm reduced fruit yields suggesting that irrigation below FC maximize yield.Soil moisture stress improved eating quality but increased BER.An intricate relationship between soil water.soil aeration and vapor pressure deficit determines the Ca 2 + transport.at least in saturated soil.needs further investigation. Figures

Fig. 1 .
Fig.1.Fruit yield with respect to soil moisture levels.

Table 1 .
Plant growth, fruit and biomass yield and fruit properties as inflneneed by soil moisture.

moisture Growth parameters Fruit and biomass Fruit quality parameters Per plant
ILeaf