EFFECT OF DIFFERENT PRE-SOWING TILLAGE ON QUANTITY AND QUALITY OF PARSNIP ( Pastinaca sativa L . ) ROOT YIELD IN RIDGE CULTIVATION

Parsnip is a very valuable vegetable due to its nutritional value and dietetic quality. It is moreover herbal raw material abundant in active substances. The yield quality of vegetables greatly depends on thorough pre-sowing soil tillage. The present study aimed at evaluating the influence of different presowing soil tillage (medium-deep ploughing, cultivating) and plant growing methods, flat or ridge cultivation, on the yield of parsnip and some biometric traits of its roots. The field experiment was carried out in 1999, 2000 and 2002 on lessive soil with the granulometric composition corresponding to medium silty loam. The parsnip cultivar ‘Półdługi Biały’ was the experimental plant species. The cultivation of parsnip on ridges had a significant influence on increased total yield of roots and decreased yield of small roots, as compared to flat cultivation. A significant increase in unit weight of the root and its diameter in the top part was also recorded in the latter type of cultivation. Spring pre-sowing tillage had no significant effect on parsnip yields. An increasing trend was observed only for total and marketable root yield in the ploughed plots. When parsnip is grown on lessive soil (which has an unstable structure), plants cultivated on ridges after spring pre-sowing plough are the most beneficial treatment combination.


INTRODUCTION
Parsnip is a vegetable with a high nutritional value and dietetic quality.The storage roots of parsnip contain considerable amounts of sugars, proteins and vitamin C, B 1 , B 2 and B 6 .The value of parsnip is also enhanced due to the content of fibre, minerals, including potassium, phosphorus, calcium, iron, as well as pectins Parsnip is valuable as herbal raw material.Its herb, roots, and fruits contain many active substances such as essential oils, flavonoids, acetylene, and furanocoumarin compounds (D y d u c h and W o l s k i , 1996).
The climatic and soil requirements of parsnip are not excessive; however, due to the fact that it is an oceanic climate species, it needs wet habitats (S k ą ps k i and D ą b r o w s k a , 1994).Water deficiency during its growing period strongly reduces plant growth and lowers yields, and moreover, it has a negative influence on the quality of harvested roots.Parsnip grows well on heavy and loamy soils, while higher yields can be achieved from habitats with good culture, humic ones, and non-crusting soils.
Root vegetables show a strong reaction to the way in which soil is prepared for sowing as well as to the plant cultivation method.Deep pre-sowing tillage determines the achievement of good quality yield of parsnip roots.Nevertheless, there are still attempts to introduce some tillage reduction consisting in the elimination of ploughing or making pre- The aim of the present study was to evaluate the influence of spring pre-sowing ploughing and shallow tillage (cultivating) as well as of plant cultivation methods, with parsnip grown on ridges or on flat ground, on its root yield and selected biometric traits of roots.

MATERIALS AND METHODS
The field experiment was carried out in 1999, 2000, and 2002 in the Felin Experimental Farm belonging to the University of Life Sciences in Lublin.
The study was conducted on lessive soil developed from loess formations with the granulometric composition of medium silty loam.Parsnip (Pastinaca sativa L.), 'Półdługi Biały', was the experimental plant species.The experimental design included the following: two methods of pre-sowing tillage with cultivating (medium-deep ploughing -to 22 cm depth and cultivating -to 15 cm depth), as well as two methods of plant cultivation: ridge and flat cultivation.Mineral fertilization was applied at the following rates: 50 kg N×ha -1 prior to sowing and 50 kg N×ha -1 post--crop, 44 kg P, and 166 kg K×ha -1 .Seeds were sown at the end of April at an amount of 8 kg×ha -1 in rows with 50 cm spacing and to a depth of 2 cm.The harvest of parsnip roots was done at mid-October.
The experiment investigated the effect of deep and shallow spring pre-sowing tillage as well as ridge and flat cultivation on total root yield, marketable root yield (root length above 20 cm, root thickness in its top part above 14 mm), yield of small roots, and some biometric traits of roots (unit weight, length, diameter).
The results were studied by means of variance analysis and the significance of differences was determined using Tukey's test at the 0.05 probability level.

RESULTS AND DISCUSSION
Total root yield.Regardless of the studied experimental factors, parsnip root yield amounted to 29.1 t per 1 hectare (Table 1).Parsnip grown on ridges produced significantly higher total root yields (by 7.8 t×ha -1 ) as compared to flat field cultivation.The positive influence of the cultivation of root vegetables on ridges was confirmed by other experiments carried out by K o n o p i ń s k i (2009) on purple salsify, which revealed significantly better yields on ridges than in flat field cultivation.Scorzonera also yielded better when grown on ridges (K o n o p i ń s k i , 2008).Carrot has been recommended for growing on ridges for many years (T a i v a l m a a and T a l v i t i e , 1997; S a i f u l -I s l a m et al.  1998) reported that, despite poor emergence, chicory and carrot yields from ridge cultivation were higher than from flat cultivation.
Different pre-sowing tillage methods applied in spring (medium-deep ploughing and cultivating), along with complementary tillage, had no significant influence on parsnip total root yields.Regardless of the cultivation method, more roots were harvested from the treatments with spring ploughing (by 0.8 t×ha -1 on average) than from the plots in which cultivating was used.Experiments done by K ę s i k et al. (1999) revealed that spring ploughing produced better effects on root yields than shallow pre-sowing soil tillage in experiments involving parsley and beetroot.Considering the interaction of tillage with the plant cultivation method, parsnip grown on ridges after spring medium--deep ploughing with cultivating appeared to be the most beneficial cultivating treatment combination.Total root yield in this treatment was higher by 7.8 t×ha -1 than in the least beneficial one -parsnip grown on flat ground after spring pre-sowing ploughing.
Marketable root yield.The yield of marketable roots amounted to 15.3 t per 1 hectare, on average (Table 2).Parsnip grown on ridges had no significant influence on marketable root yield.Regardless of spring pre-sowing soil tillage, 0.2 tons more roots were harvested from the treatments with ridges than from flat cultivation.Similar results were obtained in the study by K o n o p i ń s k i (2008) with scorzonera: higher marketable root yields were harvested on ridges.Diverse spring tillage in parsnip cultivation did not have any significant effects on marketable yield of its roots.However, slightly more roots (by 0.3 t×ha -1 ) were harvested from the plots where ploughing was applied.In experiments with beetroot, K o n o p i ńs k i (1997) achieved the highest marketable root yield due to the application of cultivating in spring, while lower yields were recorded after spring ploughing.Parsley in the study carried out by B ł a ż e w i c z -W o źn i a k (1998) reacted in a different way to pre-sowing tillage.Pre-sowing cultivation -as opposed to spring ploughing and the use of rotary tiller -had a negative influence on marketable yield of parsley roots.Among tillage and cultivation treatments applied for parsnip growing, ridges applied after pre-sowing plough tillage appeared to be the most beneficial for root yields.The marketable yield of parsnip roots in this treatment was the highest and amounted to 15.7 t×ha -1 .
Yield of small roots.Regardless of the studied factors, the yield of small parsnip roots was 2.3 t×ha -1 (Table 3).Harvested root yield was about 8.0% of total root yield.It was reported that the cultivation method had a considerable impact on the yield level of small roots.When plants grew on ridges, the amount of small roots was lower by 1.1 t ha -1 than in flat cultivation.The same correlation was reported by B a b i k and S k i e r k o w s k i (1998), who found less bent and small roots in chicory and carrots cultivated on ridges compared to those from flat cultivation.A slightly lower yield of small parsnip roots (by 0.3 t×ha -1 ) was harvested from the plots where cultivating was applied in spring.Among of the tested cultivation combinations, growing on ridges after spring cultivating of the soil was characterized by the lowest yields of small roots.
Single root weight.The studied plant cultivation methods had a significant effect on unit weight of the parsnip root (Table 4).It was found that ridge cultivation resulted in a significant increase in root weight, which was by 82 g higher than the unit weight of roots harvested from the flat field.Pre-sowing tillage played a remarkable role -although not proved statisticallyin determining the root weight.Reduced spring tillage, by applying shallow ploughing and cultivating, had a negative effect on the unit weight of the parsnip root.Regardless of the cultivation method, the unit weight of the roots harvested from the cultivated plots was lower than that of the roots from the ploughed plots.Parsley reacted in a different way to spring cultivating in the experiments performed by B ł a ż e w i c z -W o źn i a k (1998).The roots of the plants from the treatments after pre-sowing soil cultivating were characterized by higher weight.Among the tillage treatments under investigation, parsnip cultivation on ridges after spring ploughing appeared to be the best in terms of root weight.The average unit root weight from this treatment was 247 g, while the lowest value of this trait was recorded for flat field cultivation after spring ploughing (124 g, on average).
Root length.Regardless of the studied experimental factors, the mean root length was 239 mm (Table 5).Ridge cultivation had more beneficial effects (but not proved statistically) on parsnip root development.Roots harvested from ridges were longer than those from flat soil.Similar results were reported by R u m p e l and G r u d z i e ń (2000) when studying carrot cultivation.These authors found that when carrot was grown on ridges, higher and better-quality yields could be achieved.Roots were longer and with a better shape.The same conclusions were drawn by D y ś k o and K a n i s z e w s k i ( 2007) from experiments with carrot.Significantly longer black salsify roots in ridge cultivation, as opposed to flat cultivation, were obtained by K o n o p i ń s k i ( 2003).Regardless of the parsnip cultivation method, a significantly better effect of spring ploughing on root growth was recorded.Plough tillage resulted in roots by 30 mm longer compared to those harvested from the cultivated plots.Also, the longest parsley roots were produced after spring ploughing in the experiments done by B ł a ż e w i c z --W o ź n i a k (1998).Both in ridge and flat cultivation of parsnip, spring ploughing had much better effects on the value of this parameter than cultivating.
Root diameter in the top part.The applied plant cultivation methods had a significant influence on parsnip root diameter in its top section (Table 6).It was found that ridge cultivation produced better conditions for root growth, which was manifested in a 10 mm larger root diameter compared to flat cultivation.A positive impact of ridge cultivation on root thickness was also reported for scorzonera (K o n o p i ń s k i , 2003).The experiments with parsnip also revealed that spring ploughing tended to have a positive effect on the root diameter.In the plough tillage treatments, the mean parsnip root diameter was larger by 4 mm than in the plots in which cultivating was used.A similar correlation was observed in the case of scorzonera cultivation (K o n o p i ń s k i , 2003).Considering the examined factors, it should be concluded that plant cultivation on ridges after pre-sowing plough tillage was the best combination for this trait, because the average root diameter in its top part was 61 mm.Wpływ zróżnicowanej przedsiewnej uprawy roli na wielkość i jakość plonu korzeni pasternaku (Pastinaca sativa L.) w uprawie na redlinach
(O r ł o w s k i and K o ł o t a , 1999; W o l s k i et al. 1999; K u s k o w s k a , 2000; K o ł o t a et al. 2007).
sowing tillage more shallow (W ł o d e k et al. 1999; K o n o p i ń s k i et al. 1999; B ł a ż e w i c z -W o ź n i a k et al. 2001; K ę s i k et al. 2006; K o n o p i ń s k i and B ł a ż ew i c z -W o ź n i a k , 2008).
1998; R u m p e l and G r u d z i e ń , 2000; S a d y and C e b u l a k , 2000; W i e r z b i c k a et al. 2004).B a b i k and S k i e rk o w s k i (

Table 4 .
Effect of tillage and plant cultivation method on the weight of the parsnip root in g (mean for[1999][2000][2001][2002]

Table 5 .
Effect of tillage and plant cultivation method on the length of the parsnip root in mm(mean for 1999-2002)

Table 6 .
Effect of tillage and plant cultivation method on the diameter of the parsnip root in its top part in mm(mean for 1999-2002)