Nina TOTH, Josip BOROŠIĆ, Ivanka ŽUTIĆ, Bruno NOVAK

Zavod za povrćarstvo, Agronomski fakultet u Zagrebu (E-mail: nina.toth@agr.hr)

Uvod

Izravna je sjetva do nedavno predstavljala konvencionalan način uzgoja tikvice (Cucurbita pepo L. convar. giromontiina Greb.). Moderne tehnologije proizvodnje presadnica s grudom supstrata omogućuju uzgoj iz presadnica i povrtnih vrsta s osjetljivim korijenom (tikvica, krastavac, dinja i lubenica) čime se ostvaruju raniji i viši prinos u odnosu na izravnu sjetvu (NeSmith 1993; Olson et al. 1994; Brown et al. 1996; Žutić et al. 1998; Carter i Rulevich 2000). Međutim, egzistira problem određivanja optimalne starosti presadnica koja značajno utječe na komponente prinosa i vrijeme berbe (Vavrina i Orzolek 1993; Vavrina et al. 1993; NeSmith 1993; Žutić et al. 1998). Zbog introdukcije tehnologije uzgoja tikvice iz presadnica u povrćarsku proizvodnju Hrvatske sa svrhom povećanja prinosa i duže kontinuirane opskrbe tržišta, provedeno je istraživanje s ciljem potvrde mogućih prednosti takvog uzgoja uz određivanje optimalne starosti presadnica i tipa kultivara.

Materijal i metode

Istraživanje je provedeno na pokušalištu Zavoda za povrćarstvo Agronomskog fakulteta u Zagrebu tijekom tri vegetacijske sezone (1996.-1998.) u proljetno ljetnom roku uzgoja s istovremenom izravnom sjetvom i sadnjom presadnica u III dekadi svibnja. Poljski je pokus postavljen po metodi slučajnog bloknog rasporeda u četiri ponavljanja s faktorima: kultivar (2 razine: hibridni-Acceste i stranooplodni-Vegetable marrow) i startna starost biljaka (4 razine: 30, 20 i 10 dana stare presadnice te 0 dana biljke iz izravne sjetve). Osnovna je parcela bila veličine 12.96 m2 s 24 biljke razmaka 0.9 m x 0.6 m (1.8 biljaka/m2). Presadnice su proizvedene u negrijanom zaštićenom prostoru dinamikom sjetve kojom je osigurana starost presadnica 10, 20 i 30 dana radi istovremene sadnje. U sve tri godine istraživanja primijenjena su: gnojidba organskim i mineralnim gnojivima (150 kg N, 60 kg P2O5 i 250 kg K2O), malčiranje netransparentnim crno-bijelim PE filmom uz lokalizirano navodnjavanje kapanjem te potrebne mjere njege. Od početka cvatnje do kraja vegetacije na tri slučajno odabrane biljke svake parcele dva puta tjedno ženski su cvjetovi označavani datumom cvatnje zbog utvrđivanja starosti plodova. Dinamika berbe je bila dva puta tjedno u 1996. godini i tri puta tjedno u 1997. i 1998., a plodovi su sortirani na tržne (promjer manji od 6 cm), netržne (deformirani i prerasli) i abortirane. Tržnim plodovima su mjereni masa, dužina i promjer. Prvih šest berbi sudjelovalo je u formiranju ranog tržnog prinosa. Analizirane su komponente prinosa: broj plodova po biljci, prosječna masa, starost, promjer i dužina tržnih plodova, udio tržnih, netržnih i abortiranih plodova, ranozrelost, dužina razdoblja berbe te rani i ukupni prinos tržnih plodova.

Utjecaj istraživanih faktora i njihove interakcije na promatrane parametre utvrđen je metodom analize varijance, a prosječne su vrijednosti testirane Duncanovim multiplim testom rangova na razini signifikantnosti pŁ0.05.

Rezultati i diskusija

Biljke iz presadnica starosti 30 i 20 dana u sve tri godine su ostvarile najraniju berbu, opravdano raniju (16 do 21 dan) od biljaka iz izravne sjetve (tablica 1). Biljke iz najstarijih presadnica s berbom su započele značajno ranije (4 do 6 dana) i od biljaka iz najmlađih presadnica. Ranija tehnološka zrelost u uzgoju iz presadnica u usporedbi s izravnom sjetvom ustanovljena je kod dinje (NeSmith 1994), lubenice (Olson et al. 1994) i krastavca za preradu (Žutić et al. 1998). Hibridni je kultivar s berbom započeo značajno ranije (3 do 5 dana) od stranooplodnog. U 1998. godini hibridni kultivar iz presadnica starosti 30 dana iskazao je značajnu ranozrelost (3 do 14 dana) u odnosu na ostale kombinacije.

Tablica 1. Utjecaj startne starosti biljke i kultivara na ranozrelost tikvica

U sve tri godine biljke iz izravne sjetve ostvarile su opravdano najniže tržne prinose (tablica 2) što je sukladno rezultatima istraživanja s različitim vrstama iz porodice Cucurbitaceae (NeSmith 1993; Olson et al. 1994; Brown et al. 1996; Žutić et al. 1998; Carter i Rulevich 2000). Zavisno od iskazane ranozrelosti, tretiranja su sudjelovala u formiranju ranog tržnog prinosa s različitim brojem berbi (0 do 6). Usprkos značajnoj ranozrelosti biljaka iz presadnica starosti 20 i 30 dana, jedino su biljke iz presadnica starosti 20 dana u sve tri godine pripadale rangu s najvišim ranim tržnim prinosom. Hibridni je kultivar imao, sa ili bez opravdanosti, veći rani tržni prinos od stranooplodnog, a u 1998. godini u kombinaciji s presadnicama starosti 20 dana izdvojio se s opravdano najvišim ranim tržnim prinosom (2.960 kg/m2). Biljke iz presadnica starosti 10 i 20 dana u odnosu na biljke iz najstarijih presadnica ostvarile su, sa ili bez opravdanosti, viši ukupni tržni prinos. Hibridni je kultivar također imao viši ili značajno viši ukupni tržni prinos od stranooplodnog. Najviši, statistički jednak ukupni tržni prinos u 1996. godini ostvarili su hibridni kultivar iz presadnica starosti 10 i 20 dana (9.335 i 7.615 kg/m2) te stranooplodni kultivar iz presadnica starosti 20 dana (7.787 kg/m2). Pozitivan utjecaj mlađih presadnica na prinos ustanovljen je na rajčici (Leskovar et al. 1991), dok je na tikvici uočen na dinamici rasta i razvoja, ali ne i na ukupnom prinosu (NeSmith 1993).

Tablica 2. Utjecaj startne starosti biljke i kultivara na rani i ukupni tržni prinos tikvica (kg/m²)

Na razlike u visini ranog i ukupnog prinosa između godina istraživanja utjecali su temperaturni uvjeti. Pri stabilnoj srednjoj dnevnoj temperaturi zraka od 17 do 23 °C ostvarene su najviše vrijednosti ovih parametara. Utjecaj uvjeta okoline na visinu prinosa utvrdili su Vavrina et al. (1993) na lubenici i Brown et al. (1996) na tikvicama.

Zaključak

Više vrijednosti istraživanih komponenti prinosa ukazuju na prednost uzgoja tikvice iz presadnica pred konvencionalnom izravnom sjetvom te hibridnog kultivara pred stranooplodnim. Optimalna starost presadnica tikvica je 10 do 20 dana, jer nakon bržeg vegetativnog rasta ostvaruju jednaki ili viši rani i ukupni tržni prinos kao i biljke iz presadnica starosti 30 dana, a imaju ekonomičniju proizvodnju u zaštićenom prostoru zbog kraćeg ciklusa proizvodnje te mogućnost odgodnje sadnje bez rizika od redukcije prinosa, posebice najmlađe presadnice. Hibridni kultivar iz presadnica starosti 20 dana može se preporučiti za introdukciju u povrćarsku proizvodnju u Hrvatskoj zbog ranijeg plodonošenja, najvišeg ranog i ukupnog tržnog prinosa i najduže berbe.

Literatura

1. Brown J.E., Yates R.P., Chanell-Butcher Cynthia i West M.S., (1996). Planting method affects yield of summer squash. Journal of Vegetable Crop Production 2(2):51-55

2. Carter A. i Rulevich M., (2000). Use of transplants, rowcovers and black plastic to improve yield and earliness of butternut and calabaza squash. HortScience 35(3):441

3. Leskovar D.I., Cantliffe D.J. i Stoffella P.J., (1991). Growth and yield of tomato plants response to age of transplants. J. Amer. Soc. Hort. Sci. 116(3):416-420

4. NeSmith D.S., (1993). Transplant age influences summer squash growth and yield. HortScience 28(6):618-620

5. NeSmith D.S., (1994). Transplant age has little influence on yield of muskmelon (Cucumis melo L.). HortScience 29(8):916

6. Olson S.M., Hochmuth G.J. i Hochmuth R.C., (1994). Effect of transplanting on earliness and total yield of watermelon. HortTechnology 4(2):141-143

7. Vavrina Ch.S., Olson S.M. i Cornell J.A., (1993). Watermelon tranplant age: influence on fruit yield. HortScience 28(8):789-790

8. Vavrina Ch.S. i Orzolek M.D., (1993). Tomato tranplant age: A review. HortTecnology 3(3):313-316

9. Žutić Ivanka, Lešić Ružica i Novak B., (1998). Uzgoj krastavaca za preradu iz presadnica i izravnom sjetvom. Poljoprivredna znanstvena smotra 63, dodatak 4:347-351

Nina TOTH, Josip BOROŠIĆ, Ivanka ŽUTIĆ, Bruno NOVAK

University of Zagreb - Faculty of Agriculture, Vegetable Crops Department (E-mail: nina.toth@agr.hr)

Introduction

Until recently direct sowing presented the convential cultivation method of the summer squash (Cucurbita pepo L. convar. giromontiina Greb.). Modern technologies of producing transplants with a substrate lump enable cultivating vegetable species with sensitive roots from transplants as well (summer squash, cucumber, melon and watermelon), and are instrumental in achieving earlier and higher yields when compared with direct sowing (NeSmith 1993; Olson et al. 1994; Brown et al. 1996; Žutić et al. 1998; Carter and Rulevich 2000). There is, however, the problem of determining the optimum transplant age, which has a significant influence on yield components and harvest date (Vavrina and Orzolek 1993; NeSmith 1993; Žutić et al. 1998). Due to the introduction of the cultivation method of the summer squash from transplants into the vegetable production in Croatia with the aim of yield improvement and prolonged continuous market supply, a reasearch was conducted to prove possible advantages of such cultivation and determine the optimum transplant age and cultivar type.

Material and Methods

The research was conducted on a trial plot of the Vegetable Crops Department in Zagreb during three vegetation seasons (1996-1998) in the spring-summer cultivation term with simultaneous direct sowing and planting of transplants in the III decade of May. The field trial was conducted in randomized block design with 4 replications, with the factors: cultivar (2 levels: hybrid Acceste and open pollinated Vegetable marrow) and initial plant age (4 levels: 30, 20 and 10 day old transplants, and 0 day old plants from direct sowing). The base plot's size was 12.96 m2 with 24 plants spaced at 0.9 m x 0.6 m (1.8 plants/m2). Transplants were produced in unheated greenhouse with sowing dynamics which ensured transplant ages of 10, 20 and 30 days for simultaneous planting. Fertilization with organic and mineral fertilizers (150 kg N, 60 kg P2O5 and 250 kg K2O), and mulching with opaque black/white PE film with localized drip irrigation was applied during the research. From the start of flowering to the end of vegetation female flowers on three randomly selected plants on each plot were marked twice a week with date of flowering to determine the age of the fruit. Harvest dynamics consisted of two (1996) and three (1997 and 1998) harvests a week. Fruits were sorted as marketable (diameter ? 6 cm), unmarketable (deformed and overgrown) and aborted. Mass, length and diameter of marketable fruits were measured. First six harvests were performed the early market yield. Analyzed yield components: number of fruits/plant, mass, age, diameter and length of marketable fruits, ratio of marketable, unmarketable and aborted fruits, earliness, length of harvest period as well as early and total market yield. The influence of researched factors and their interaction on the observed parameters was determined by the variance method, while the average values were tested according to the Duncan's Multiple Range Test at a significance level of pŁ0.05.

Results and Discussion

Plants from 30 and 20 day old transplants in all three years had the earliest harvest, justifiably earlier (16 to 21 days) than the plants from direct sowing (Table 1). Plants from the oldest transplants started the harvest significanly earlier (4 to 6 days), even than plants from the youngest transplants. Earlier technological maturity of cultivation from transplants in comparison with direct sowing was determined for melon (NeSmith 1994), watermelon (Olson et al. 1994) and pickling cucumber (Žutić et al. 1998). The hybrid cultivar started the harvest significantly earlier (3 to 5 days) than the open pollinated. In 1998 the hybrid cultivar from 30 day old transplants showed significant earliness (3 to 14 days) in comparison with other combinations.

Table 1 Influence of initial plant age and cultivar on earliness of the summer squash

In all three years the plants from direct sowing achieved justifiably lowest market yields (Table 2), which is consistent with research results on cucurbits (NeSmith 1993; Olson et al. 1994; Brown et al. 1996; Žutić et al. 1998; Carter and Rulevich 2000). Depending on their earliness, the treatments were included into the early market yield with different number of harvests (0 to 6). Despite significant earliness of the plants from 20 and 30 day old transplants, only the plants from 20 day old transplants in all three years belonged to the rank with the highest early market yield. The hybrid cultivar had, justifiably or unjustifiably, a higher early market yield than the open pollinated, and in 1998, in combination with the 20 day old transplants was singled out with the justifiably highest early market yield (2.960 kg/m2). The plants from 10 and 20 day old transplants, in comparison with the plants from the oldest transplants, achieved, justifiably or unjustifiably, a higher market yield. The hybrid cultivar also had a higher or significantly higher total market yield than the open pollinated. The highest, statistically equal total market yields in 1996 were achieved by the hybrid cultivar from 10 and 20 day old transplants (9.335 and 7.615 kg/m2) and the open pollinated cultivar from 20 day old transplants (7.787 kg/m2), as well. A positive influence of the younger transplants on the yield was determined for tomato (Leskovar et al. 1991), whereas for summer squash it applied to the dynamics of growth and development, but not the total yield (NeSmith 1993).

Table 2 Influence of initial plant age and cultivar on early and total market yield of the summer squash (kg/m²)

The differnces between the early and total yields for individual research years were influenced by temperature conditions. At stable average air temperature of 17 to 23 °C the highest values of the parameters were achieved. The influence of environment conditions on yield was determined by Vavrina et al. (1993) for watermelon and Brown et al. (1996) for summer squash.

Conclusions

The higher values of researched yield components suggest the advantages of cultivating summer squash from transplants over conventional method of direct sowing, and the hybrid cultivar over the open pollinated. The optimum age of summer squash transplants is 10 to 20 days, since following faster vegetative growth they achieve equal or higher early and total market yield then plants from 30 day old transplants. Their production in protected spaces is more economical due a shorter production cycle and a possibility of delaying planting without the risk from reduction in yield, which particularly applies to the youngest transplants. The hybrid cultivar from 20 day old transplants can be recommended for introduction into the vegetable production in Croatia due to its earlier fruit-bearing, the highest early and total market yield and the longest harvest period.

References

1. Brown J.E., Yates R.P., Chanell-Butcher Cynthia i West M.S., (1996). Planting method affects yield of summer squash. Journal of Vegetable Crop Production 2(2):51-55

2. Carter A. i Rulevich M., (2000). Use of transplants, rowcovers and black plastic to improve yield and earliness of butternut and calabaza squash. HortScience 35(3):441

3. Leskovar D.I., Cantliffe D.J. i Stoffella P.J., (1991). Growth and yield of tomato plants response to age of transplants. J. Amer. Soc. Hort. Sci. 116(3):416-420

4. NeSmith D.S., (1993). Transplant age influences summer squash growth and yield. HortScience 28(6):618-620

5. NeSmith D.S., (1994). Transplant age has little influence on yield of muskmelon (Cucumis melo L.). HortScience 29(8):916

6. Olson S.M., Hochmuth G.J. i Hochmuth R.C., (1994). Effect of transplanting on earliness and total yield of watermelon. HortTechnology 4(2):141-143

7. Vavrina Ch.S., Olson S.M. i Cornell J.A., (1993). Watermelon tranplant age: influence on fruit yield. HortScience 28(8):789-790

8. Vavrina Ch.S. i Orzolek M.D., (1993). Tomato tranplant age: A review. HortTecnology 3(3):313-316

9. Žutić Ivanka, Lešić Ružica i Novak B., (1998). Uzgoj krastavaca za preradu iz presadnica i izravnom sjetvom. Poljoprivredna znanstvena smotra 63, dodatak 4:347-351