Influence of Harvest Method and Schedule on Yield and Spear Size of
Green Asparagus in Indonesia.
Tino Mutiarawati Onggo Faculty of Agriculture University of Padjadjaran
Jl. Raya Bandung-Sumedang km 21 Jatinangor, Indonesia.
Keywords: Asparagus officinalis, mother-stalk method, alternate harvest.
Abstract
In tropical climates such as Indonesia, asparagus growth does not have any dormant period. The high temperature throughout the year maintains high rates of plant growth and consequently reduced long term plant productivity. The objective of this experiment was to find the best combination of harvest method and schedule to maximize spear yield and size of green asparagus during a 20 week harvest period in the rainy season. The harvest methods tested were : a0 (without mother
stalk (MS)), a1 (with one MS) and a2 (with two MS). The harvest schedules were : p1
(4H – 8R – 8H), i.e. 4 weeks harvesting, 8 weeks rest and 8 weeks harvesting, p2 (6H
– 8R – 6H) and p3 (8H – 8R – 4H). The best harvest schedule depended on the
harvest method. Harvesting without MS increased the number of spears, but spear size decreased rapidly, so this method produced a lower percentage of marketable yield. Harvesting with one MS slowed down spear size decrease, so that the average spear size produced was larger than in harvesting without MS. Combining this method with the p2 and p3 harvest schedules produced significantly better
spear size. Harvesting with 2 MS also produced better spear size but fewer spears and lower yield when combined with harvest schedule p1.
INTRODUCTION
Harvesting of asparagus in temperate zones occurs in spring and is carried out by cutting off all new spears. During the following summer and autumn, fern growth produces reserves which are stored in roots and rhizomes; subsequently in the winter/cold season the crop becomes dormant (Hartman, 1989). In semi-temperate zones such as Taiwan the crop does not experience dormancy, but growth slows during the hot summer and cold winter seasons. In these areas high yields can be achieved by adopting the mother-stalk harvesting method, which is done for 3-4 months in spring and 2-3 months in fall ( Hung & Huang, 1987; Wang, 1983; Chen, 1983).
spear number and yield are low. To obtain high yields and good spear quality in Indonesia, the best combination of method and schedule needs to be determined.
The objectives of this experiment was to find out the best combination between number of spears left in mother-stalk method and alternating harvest period to produce good yield and better quality of spears for tropical region.
MATERIAL AND METHODS
The experiment was carried out on a two year old (2nd year harvest) crop of cv. Mary Washington in Arjasari – Bandung, West- Java, about 800 m above sea level where the mean daily temperature in the rainy season is 220 – 260C. A double row system of planting with plant distances (60 cm x 40 cm)(80 cm x 40 cm) and planting depth of 15 cm was employed. The crop was not harvested during the dry season; harvesting commenced at the beginning of the rainy season (October 2000) by cutting off all stems. Spears growing in the no-mother-stalk treatments were harvested immediately, while in the mother-stalk (MS) treatments the first spears were left to grow to become stalks. The number of stalks left per plant in each plot was adjusted according to the treatments. The following spears were then harvested. After the first harvest period the crop was left not harvested for eight weeks, then harvesting commenced again and continued with the same method until the completion of the harvesting period. A simple randomised block design with three replicates was used. The complete harvest period was 20 weeks in all treatments. Plot size was 8.4 m2 (1.4 m x 6.0 m), containing 30 plants. With three methods of harvesting combined with three harvest schedules, there were a total of nine treatments as follows:
aop1 : without MS, harvest schedule (4H – 8R– 8H) = 4 weeks harvesting, 8 weeks rest (no harvesting), 8 weeks harvesting again
aop2 : without MS, harvest schedule (6H – 8R – 6H) a0p3 : without MS, harvest schedule (8H – 8R – 4H) a1p1 : with 1 MS, harvest schedule (4H – 8R – 8H) a1p2 : with 1 MS, harvest schedule (6H – 8R – 6H) a1p3 : with 1 MS, harvest schedule (8H – 8R – 4H) a2p1 : with 2 MS, harvest schedule (4H – 8R – 8H) a2p2 : with 2 MS, harvest schedule (6H – 8R – 6H) a2p3 : with 2 MS, harvest schedule (8H – 8R – 4H) The following yield characteristics were measured:
1. Number of spears per plot during the 20 week 2. Total spear weight per plot
3. Average spear weight / spear size
4. Number and weight of marketable spears per plot
5. Percentage of marketable yield (number and weight of spears)
RESULTS AND DISCUSSION Number of Spears and Spear Weight
The number of spears and spear weight per plot during the 20 week are presented in Table 1. The non mother-stalk treatments produced the most spears. Treatment a0p3 (without MS, harvesting schedule (8 – 8 – 4)) produced the largest number of spears, and it was significantly higher than the treatments with one and two MS and the same harvest schedule. On the other hand, treatments with 2 MS produced the lowest number of spears with the p1 harvest schedule (4 – 8 - 8). Beside producing the most spears, treatment a0p3 also gave the highest yield, although statistically it did not differ from the other
combination treatments except for a2p1, which produced the least weight of spears.
The without MS method of harvesting, i.e. cutting off all developing spears, stimulates budding which continues as long as environmental conditions are conducive for growth. Rate of spear development and spear size depend greatly on the amount of reserves stored in the crown. Environmental conditions at the experimental location, such as ambient temperature during the rainy season, did not inhibit plant growth; in fact they greatly supported spear growth. Moreover, adequate reserves in the crown were available due to the no harvest period in the previous dry season. Consequently, the highest number of spears was found in the without MS treatment (a0) combined with the longest harvest session at the beginning of the schedule (p3). On the other hand the treatment with two MS produced the least spears because, as long as the ferns are growing, apical dominance inhibits spear initiation until fern growth is terminated. (Wilcox – Lee and Drost, 1991 in Drost, 1997). This apparently requires a sufficient length of time, as shown by the harvest schedule p3 (4 - 8 - 8); during the first four weeks plant growth was centered on expansion of the two spears to become stalks; during the following eight weeks the plant was given rest (not harvested); and finally it was harvested for eight weeks. Consequently in this combination treatment the real harvest was in fact carried out only in the second part of the harvesting schedule, and the result was a low yield.
In the treatment with one MS, the plant condition is in between the two extremes discussed above. Spear number and weight per plot per harvest period did not differ significantly during the three levels of harvest schedule.
Average Spear Weight
Although the number of spears was high in the without MS treatments, total spear weight was not significantly differ from the other treatments because mean spear weight was low. ( Table 2 ). Harvesting over a pro-longed period of time without MS depleted reserves in the crown, with no new supplies being produced, and, consequently spear size decreased rapidly. Spear weight is related directly to diameter and length. In this experiment harvesting was done every day. Spear length was consistent (20 cm – 25 cm) so the reduction of spear weight was caused by decreasing diameter. Minimum marketable spear diameter in this study was set at 0.8 cm.
Marketable Number and Weight of Spears
number and weight of spears produced by the one and two MS treatments at all levels of harvesting did not differ significantly.
CONCLUSIONS
Marketable number and weight of green asparagus spears did not significantly among the treatments tested in this study, except for treatment a2p1 which produced the lowest values. However, there was an interdependency between method of harvesting and harvest schedule. The without MS method of harvesting produced more spears than the MS methods. The treatment that combined without MS and the (8H – 8R – 4H) harvest schedule produced the highest yield, but also caused spear size to decrease rapidly. Consequently, at all levels of harvesting schedule percentages of marketable spear yield, in both numbers as well as weight, were low.
The one MS method of harvesting reduced spear size decline and produced larger mean spear size than the without MS harvesting method. The latter method of harvesting in combination with the harvest schedule of p2 (6H – 8R – 6H) and p3 (8H - 8R – 4H) produced significantly larger spear size. The two MS method of harvesting also produced large spears, but spear number was less, causing the overall yield of spears to be low if this method was combined with the harvesting schedule of p1 (4H – 8R – 8H).
ACKNOWLEDGEMENTS
I wish to thank Mr. Suphendi for technical assistance during the experiment.
Literature Cited
Chen, Y.W. 1983. The Growth of Green Asparagus Spears in Tropical Region (Taiwan). Taiwan Asparagus Research Report. (3): 388 – 390.
Drost, D.T. 1997. Asparagus. In The Physiology of Vegetable Crops. Wien, H.C. (Editor). CAB International, Oxon, UK.
Hartmann, H.D. 1989. Spargel – Grundlagen fuer den Anbau. Eugen Ulmer GmbH & Co, Stuttgart, Germany.
Hung, L. and H. Huang. 1987. Asparagus Breeding in Subtropical Taiwan. Improved Vegetable Production in Asia. (36) : 128 – 135.
Tables
Table 1 : Number of spears and spear weight of green asparagus per plot during the 20 week harvesting period.
Combination Treatment Number of Spears/plot Spear Weight/plot Method , Schedule (g) aop1 : without MS, (4 – 8 – 8) 199.5 ab 1936.4 ab aop2 : without MS, (6 – 8 – 6) 190.9 ab 1940.9 ab aop3 : without MS, (8 – 8 – 4) 261.2 a 2710.2 a a1p1 : with 1 MS, (4 – 8 – 8) 173.4 ab 1901.1 ab a1p2 : with 1 MS, (6 – 8 – 6) 152.4 b 2182.7 a a1p3 : with 1 MS, (8 – 8 – 4) 149.3 b 2074.9 a a2p1 : with 2 MS, (4 – 8 – 8) 98.6 c 1312.2 b a2p2 : with 2 MS, (6 – 8 – 6) 169.4 ab 2328.1 a a2p3 : with 2 MS, (8 – 8 – 4) 130.6 bc 2018.4 a
_____________________________________________________________________ * MS = Mother-stalk
** Mean separation in columns by Duncan’s Multiple Range Test, 5% level.
Table 2 : Mean spear weight of green asparagus during the 20 week harvesting period.
Combination Treatment Mean Spear Weight ( g ) Method , Schedule
aop1 : without MS, (4 – 8 – 8) 9.7 d aop2 : without MS, (6 – 8 – 6) 10.2 cd aop3 : without MS, (8 – 8 – 4) 10.5 cd a1p1 : with 1 MS, (4 – 8 – 8) 11.1 bcd a1p2 : with 1 MS, (6 – 8 – 6) 14.3 ab a1p3 : with 1 MS, (8 – 8 – 4) 14.0 ab a2p1 : with 2 MS, (4 – 8 – 8) 13.4 abc a2p2 : with 2 MS, (6 – 8 – 6) 13.9 ab a2p3 : with 2 MS, (8 – 8 – 4) 15.5 a * MS = Mother-stalk
Table 3 : Number of marketable spear and marketable yield of green asparagus per Plot during the 20 week Harvesting Period.
____________________________________________________________________ Combination Treatment Number of Marketable Marketable Spear Weight Method, Schedule Spear per Plot per Plot ( g) aop1 : without MS, (4 – 8 – 8) 89.3 ab 1321.3 ab aop2 : without MS, (6 – 8 – 6) 86.5 ab 1291.2 ab aop3 : without MS, (8 – 8 – 4) 131.5 a 1936.4 a a1p1 : with 1 MS, (4 – 8 – 8) 107.2 a 1520.5 ab a1p2 : with 1 MS, (6 – 8 – 6) 105.7 a 1725.8 a a1p3 : with 1 MS, (8 – 8 – 4) 105.9 a 1721.8 a a2p1 : with 2 MS, (4 – 8 – 8) 63.7 b 984.0 b a2p2 : with 2 MS, (6 – 8 – 6) 118.9 a 2152.7 a a2p3 : with 2 MS, (8 – 8 – 4) 87.5 ab 1588.5 a
_____________________________________________________________________ * MS = mother-stalk
** Mean separation in columns by Duncan’s Multiple Range Tests, 5% level
Table 4: Percentage marketable spear by number and weight of green asparagus during the 20 week harvesting period.
_____________________________________________________________________ Combination Treatment Number of Marketable Weight of Marketable Method, Schedule Spears (%) Spears (%)
aop1 : without MS, (4 – 8 – 8) 44.97 d 68.43 b aop2 : without MS, (6 – 8 – 6) 46.17 cd 67.03 b aop3 : without MS, (8 – 8 – 4) 51.90 bcd 71.93 ab a1p1 : with 1 MS, (4 – 8 – 8) 62.10 abc 80.13 ab a1p2 : with 1 MS, (6 – 8 – 6) 69.73 a 79.37 ab a1p3 : with 1 MS, (8 – 8 – 4) 71.23 a 83.07 a a2p1 : with 2 MS, (4 – 8 – 8) 64.63 ab 75.30 ab a2p2 : with 2 MS, (6 – 8 – 6) 70.13 a 80.43 ab a2p3 : with 2 MS, (8 – 8 – 4) 67.07 ab 78.70 ab
_____________________________________________________________________ * MS = mother-stalk
