| Sažetak | Lubenica je važna poljoprivredna kultura, uzgaja se radi ploda peponisa, koji se iskorištava u
tehnološkoj zrelosti, a konzumira najčešće svjež. Iako sadrži preko 90 % vode, plod je bogat
nutritivnim i antioksidativnim spojevima. Lubenica je jednogodišnja termofilna kultura i visokih
zahtjeva za količinom svjetla. Dušik je jedno od najznačajnijih i najzastupljenijih
makrohraniva za formiranje prinosa i kvalitete plodovitog povrća. Intenzivna poljoprivredna
praksa te istraživanja upućuju na obročnu gnojidbu lubenice dušikom, fertirigacijom po
pojedinim fenofazama, u različitim preporučenim dozama. Lubenica se u intenzivnoj
poljoprivrednoj praksi najčešće uzgaja na crnom polietilenskom (PE) filmu koji uz mnoge
druge dobrobiti povećava i iskoristivost hraniva. Malčevi utječu još i na mikroklimatsko
okruženje biljke: temperaturu tla u zoni korijena, apsorpciju i refleksiju svjetla od malča te na
dostupnost fotosintetski aktivne radijacije (FAR). Ciljevi istraživanja bili su utvrditi optimalnu
razinu dušika i tip malča koji će najbolje utjecati na vegetativni rast, prinos i kvalitetu ploda
lubenice te najpovoljniji učinak na mikroklimatsko okruženje lubenice i sve mjerene
pokazatelje. Dvogodišnji poljski pokus s dva faktora postavljen je po metodi split-plot u tri
ponavljanja na lokaciji u blizini Pule, u Istri. Gnojidba dušikom bila je glavni faktor u četiri
razine (kontrola, 60, 120 i 180 kg N ha-1), a malčiranje podfaktor u tri razine (nepokriveno tlo,
slama pšenice, crni PE-film). Prikupljani su i mikroklimatski podaci o temperaturi tla i zraka te
količina reflektiranog FAR-a. Mjereni su pokazatelji vegetativnog porasta, ukupan dušik lista,
HNT broj, pokazatelji fotosinteze, prinos i sastavnice, fizikalna svojstva i topiva suha tvar
ploda te senzorna analiza ploda uz pomoć panela. Više doze dušika nisu utjecale na
povećanje vegetativnog rasta, ukupnog prinosa, i sastavnica, sadržaja topive suhe tvari
ploda, ali su utjecale na višu organoleptičku ocjenu ploda lubenice u obje godine. Malčiranje
crnim PE-filmom, najpovoljnije je utjecalo na rani vegetativni rast lubenice, viši HNT broj lista
lubenice, na prinos i sastavnice u ranim berbama 2010. godine. S druge strane, u kasnim
berbama 2010. godine najviši broj i prinos tržnih plodova imale su lubenice uzgajane na
slami. Upotreba crnog PE-filma djelovala je povoljnije od ostalih malčeva na sumu toplinskih
jedinica u zoni korijena (STT) te na tjedne prosječne temperature pet centimetara ispod tla,
dok je najveća refleksija FAR zabilježena pri malčiranju slamom. Kombinacija crni PE-film uz
kontrolnu gnojidbu od 42 kg N ha-1 dovoljna je za pozitivne vrijednosti vegetativnog rasta,
ranog prinosa te fizikalnih svojstava ploda. Za najvišu organoleptičku kvalitetu ploda, uz crni
PE-malč dovoljna je gnojidba od 60 kg N ha-1. Najpovoljnije mikroklimatske uvjete, prosječnu
tjednu temperaturu i STT, moguće je postići malčiranjem crnim PE-filmom. |
| Sažetak (engleski) | Watermelon is grown all over the world at 3.5 million ha with production of a 117 million tons,
tons, most of which is in Asia (82.6 %) and only 5.7 % in Europe. Watermelon prefers dry,
warm climate and is very sensitive to frost. It is grown for its fruit peponis, which is mostly
consumed fresh. In the chapter Overview of previous research presented studies show how
nitrogen has a key role in all meristem functions, photosynthesis and protein synthesis in all
plant organs. Nitrogen fertilization is necessary to obtain high crop yields, however. There is
a strong possibility of nitrogen leakage and ground water contamination especially in karst
regions like Istria. Fertirrigation is a widely used technology of vegetable production which
provides water and nutrients necessary for plant growth. Common agricultural practice for
intensive watermelon productions based on soil mulching with black PE-film and
fertirrigation. Straw mulch or bare ground is usually used in organic agriculture. Effects of soil
mulching with polyethylene (PE) mulches, especially with black PE-film, are higher early
growth and yield, higher number of fruits and total yield, better water and mineral uptake and
crops pest resistance. Depending on material characteristics, various polymer or plant
mulches have different impacts on crops, which could be seen as effects on plants
microclimate: temperature and available photosynthetically active radiation (PAR). Studies
show how the most influential microclimate factor is the root zone temperature (RZT), which
rises under black PE-mulch, but decreases under straw mulches, compared to bare ground.
Enhanced RZT stimulates root growth, water and minerals uptake and results in a higher
growth degree day’s sum. In the chapter Material and methods the course of research and
data processing is presented. The aim of the research was to determine nitrogen rate and
mulch type impact on watermelon early vegetative growth, yield, fruit quality and watermelon
microclimate conditions. Two-year field trial was set up in Valtura (44°52’52.7”N;
13°53’52.8”E), south Istria as two factorial experiment according to split–plot scheme with
three replications. The first factor was additional nitrogen rate: 0 – control, 60, 120 and 180
kg N ha-1 and the second factor was mulch type: bare ground, straw and black PE-film. Data
was collected on vegetative growth parameters (main vine length, diameter and number of
leaves, number of secondary vines longer than 2.5 cm), total leaf nitrogen, HNT index,
photosynthesis parameters, yield components fruit physical parameters and soluble dry
matter, and also fruit panel sensory evaluation. Microclimate data was collected: RZT was
measured with temperature sensors placed under mulches, 5 cm below the soil surface, also
air temperature 5 cm above the soil and mulches and PAR reflected from the soil and mulch
surface. The obtained results of the research showed that higher nitrogen doses didn’t
increase vegetative growth, total yield and yield components, fruit soluble dry matter, but
increased fruit sensory ratings in both years.
Black PE-film increased early vegetative growth, higher HNT index, early yield and yield
components in 2010. Straw mulch had the highest marketable fruit yield and number in late
harvests of 2010. Black PE-film had higher growing degree days sum (GDD) and higher
weekly average temperature 5 cm below the surface than straw mulch and bare ground.
Highest reflected PAR was recorded on straw mulch. Black PE-film and nitrogen fertilization
of 42 kg ha-1 is enough for high early vegetative growth results, early yield and fruit physical
parameters. Black PE – film with nitrogen fertilization of 60 kg ha-1 is enough for achieving
the highest organoleptic fruit quality. The best microclimate conditions for watermelon
growth: highest weekly average temperature and GDD, was achieved with usage of black PE
–film as mulch. |
