2.1 Experimental site The experiment was conducted at the FTIP Germplasm Centre of the Bangladesh Agricultural University (FTIP BAU-GPC), Mymensingh during the period from July, 2017 to October, 2018 to study the effects of fruit thinning on the off-season quality guava production.
2.2 Climate and soil The experimental area was located under the subtropical climate, characterized by heavy rainfall during the months of June to September and scanty rainfall during rest of the period of the year. The site of the experiment was medium high land, which belongs to the Old Brahmaputra Floodplain under the Agro-Ecological Zone 9 having non-calcareous dark gray floodplain soil (UNDP-FAO, 1988). The land was medium high, fertile, well drained and slightly acidic with soil pH varying from 5.5 to 6.8. The amount of organic carbon, total N, available P and K were 0.835%, 0.068, 18 ppm and 0.28 me 100g−1 of the soil samples, respectively.
2.3 Treatments and design The experiment was carried out in a randomized complete block design (RCBD) with 3 replications. The experiment consisted of two factors, viz., (A) 2 varieties of guava (Swarupkathi and BAU Peyara-5, and (B) 6 levels of fruit thinning. The characteristics of the varieties and description of the fruit thinning operations are described below:
Swarupkathi Swarupkathi is a medium sized tree of 4 years aged with leaves relatively small and pale green in colour. It bears fruits throughout the year. Average weight of fruit is 70-150 g and may attain upto 300 g. Fruits are globose to round shaped with rough surface. Medium sized fruit is greenish white in colour. Endosperm is whitish, sweet in taste and flavoured. Low seeded fruit, which pulp crispy to soft in texture. This variety is widely cultivated at the Barisal of Bangladesh.
BAU Peyara-5 BAU Peyara-5 is a high yielding fruit variety, produces fruits twice in a year. It is large pearshaped fruits (445 g) with creamy white flesh pulp. Pulp is crispy and slight sour in test (TSS 8.0%). Plant height is medium, ripe fruit colour is yellowish green, on an average 340-360 seeds present per fruit, seeds are hard, on average 1000-seed weight is around a 3.5-4 g. Fruit setting starts within one year after plantation. Fruits are stored in normal temperature from 7 to 10 days. Fruit contains 210 mg 100g−1 vitamin C. The yield of BAU Peyara-5 is 28 t ha−1.
T1 (0%) No fruit thinned from the plant; T2 (20%) In this treatment, from each replication total number of fruits plant−1 was counted after fruit set. Out of these, 20% fruits were thinned randomly by hand when the mean weight of individual fruit was 15-20 g (Mamun et al., 2013); T3 (40%) In this treatment, from each replication total number of fruits plant−1 was counted after fruit set. Out of these, 40% fruits were thinned randomly by hand when the mean weight of individual fruit was 15-20 g; T4 (60%) In this treatment, from each replication total number of fruits plant−1 was counted after fruit set. Out of these, 60% fruits were thinned randomly by hand when the mean weight of individual fruit was 15-20 g; T5 (80%) In this treatment, from each replication total number of fruits plant−1 was counted after fruit set. Out of these, 80% fruits were thinned randomly by hand when the mean weight of individual fruit was 15-20 g; T6 (100%) In this treatment, from each replication total number of fruits plant−1 was counted after fruit set. All the fruits were thinned by hand when the average weight of individual fruit was 15-20 g. Generally the effects of 100% fruit thinning during on season produce better number of fruits during the offseason. For each variety 18 plants were selected for the study. All fruits under taken for data collection during off-season.
during off-season. In each replication total number of fruits plant−1 was counted after fruit set. Out of these, fruits were thinned by hand randomly according to the treatments after 20 days of fruit setting and before the natural dropping when the mean weight of individual fruit was 15-20 g.
2.4 Intercultural operations Weeding was done at an interval of 15 days up to fruit set and it was continued at an interval of ten days from fruit set to harvest. These were controlled by niri and spade. Fertilizers @ 200 g urea, 100 g TSP, 200 g MoP and 100 g Zinc, and 10 kg well decomposed cowdung were applied plant−1 of 15th days before fruit thinning. Manures were applied through ring placement. Irrigation was applied during on-and off-season. During off-season water is required more than on-season. Flood irrigation and drain method was maintained during irrigation after and before flower set. During on-and-off season disease and pest are harmful for production. During on-season Furadan @ 3 mL L−1 was applied to remove guava fruit fly. Different kind of cupper and sulfer fungicide were applied to avoid different disease. In the experiment 10 fruits were selected at random from each plant labelled and the fruits were harvested by hand picking at regular intervals at mature stage when yellowish green colour developed. This stage is mostly liked for consumption (Singh, 1995).
2.5 Parameters measured Experimental data were recorded from the plants on the following parameters (from fruit thinning). Number of flower set plant−1 The number of flowers plant−1 was recorded up to 1st July, 2017 (during on season) and 15th October, 2017 (during off-season). Number of fruit set plant−1 The number of fruits set plant−1 was recorded up to 25th July, 2017 (during on season) and 20th November, 2017 (during offseason). Fruit yield plant−1 Fruits at different days and yield plant−1 was recorded in kg and the total harvested fruits were calculated as yield plant−1. Total soluble solids (TSS) Total soluble solids (TSS) were recorded in percentage by the hand refractometer from extracted juice of the sample fruits.
2.6 Statistical analysis The analyses of variance (ANOVA) of the parameters under study were performed using F-variance test. The significance of the differences in mean of the treatment was calculated using least significant difference (LSD) test at 1 and 5% levels of probability