Technical and Field Evaluation of Tractor Operated Frontal Pre-pruner for Kinnow Mandarin (Citrus reticulata) and Guava (Myrtaceae) Orchard

Fruit tree pruning is the cutting and removing of selected parts of a fruit tree. It spans through quite a number of horticultural techniques. Pruning includes cutting branches back, sometimes removing smaller limbs entirely and more so the removal of young shoots, buds and leaves. Established orchard practice of both organic and nonorganic types typically includes pruning. Pruning can control growth, remove dead or diseased wood, and stimulate the formation of flowers and fruit buds. Pruning and training young trees improves their later productivity and longevity and can also prevent later injury from weak crotches or forks (where a tree trunk splits into two or more branches) that break from the weight of fruit, snow, or ice on the branches. However, the efficiency of pruning methods is also important. Manual pruning has constraints like lower field Capacity and incomplete pruning in case of tall trees. Therefore, a tractor operated 1-row frontal pre-pruner with electro hydraulic control was tested for Kinnow Mandarin and Guava orchards. The time involved for top and side pruning was 23.30 and 46.80 min/acre, respectively and there was 99.32-99.38% saving in time as compared to manual pruning.


Introcution
Mandarin orange (Citrus reticulata) is the most common citrus fruits grown in India. It occupies nearly 40% of the total area under citrus cultivation in India. The most important commercial citrus species in India are the mandarin (Citrus reticulata), sweet orange (Citrus sinensis) and lime lemon (Citrus limon) sharing 41, 23 and 23%, respectively of all citrus fruits produced in the country with an area of 0.428, 0.185, 0.286 million ha and production rate of 5.1, 3.27 and 3.15 million metric tons, respectively (Anonymous, 2018). Citrus (Citrus sp., Rutaceae) is cultivated in the states of Maharashtra, Andhra Pradesh, Punjab, Himachal Pradesh, Uttar Pradesh, Madhya Pradesh, Karnataka, Jammu and Kashmir, Orissa, Gujarat, Assam, Meghalaya, Rajasthan, Sikkim and Tamil Nadu. It is an evergreen medium to tall erected tree. It grows to a maximum height of 25 m (Anonymous, 2020a). In India, Guava (Psidium guajava, Myrtaceae) is successfully grown in Uttar Pradesh, Bihar, Madhya Pradesh, Maharashtra, West Bengal, Orissa and Tripura. Uttar Pradesh is considered as the most important guava producing state in India, and the Allahabad-Varanasi region has the reputation of growing the best quality guava in the country as well as in the world. It is a hardy and tall tree with height of more than 2.5 m (Anonymous, 2020b). In most developing countries, manual pruning are used whereas in developed countries mechanical pruner are used. Pruning is at the heart of arboriculture, one of the most important services arborists provide (Clark & Matheny, 2010). In the next future it is expected that greater use of wireless and lightweight equipment will be done to assess worker exposure to musculoskeletal disorders not only in pruning but in all farming operations (Elio et al., 2014). The results suggested that maintaining a live crown ratio of 55% would minimize effects of pruning on diameter growth. The effect of severe pruning on diameter increment was greater for subdominant trees than for dominant stems (Neilsen & Pinkard, 2011). In economic terms, if the rows are 400 m long, then the surface area suitable for mechanical pruning is 10 to 11 ha for all three varieties. There was no visible damage to the fruit branches with the mechanical pruner, but some damage occurred to wires with a diameter of less than 1.8 mm (Gambella & Sartori, 2014). Canopy management system labour operation cost estimates indicated a labour saving of 62% and 80% with mechanical prepruning with hand shoot thinning (MPDHT) and mechanical box-pruning with mechanical shoot thinning (MPDMT) treatments, respectively when compared with hand pruning (HP) for 'Cabernet sauvignon' grape (Vitis vinifera). All treatments had similar yield, total soluble solids (TSS), juice pH, and titratable acidity (TA), Berry skin total phenolics, anthocyanins, and tannins at harvest. All treatments tested were within acceptable Ravaz index limits of 5 to 10 lb/lb. However, only MPDMT treatment reached a near optimum leaf area to fruit ratio of 1.2 m 2 kg -1 and pruning weight of 1.0 kg m -1 for warm climate viticulture (Kurtural et al., 2012). Sanding and pruning are two practices used in the cranberry (Vaccinium macrocarpon) industry for vine management and yield stimulation. Cumulative yield and net returns were higher in light severity treatments compared to those in the moderate and heavy treatments. Moderate and heavy sanding treatments were associated with lower yields and net returns than those for the untreated controls (Suhayda et al., 2009). Chancellor cited in Persson (1987), Kempe (1967) and Johnston (1968a and1968b) also reported that the cutting force required when pruning a range of herbaceous (Phleum pratense) and woody (Picea glauca, Pinus resinosa, Pinus banksiana, Pinus taeda, Pinus radiata, Abies balsamea) up to 18 cm thick materials was greatly affected by the knife thickness. In some cases, doubling the knife thickness resulted in 50% increase in the cutting force. Mattson and Sturos (1996) on the other hand, found that knife thickness did not affect cutting force required to shear sugar maple (Acer sacharum) branches. This may have been due to lower cutting speeds (> 600 mm/sec compared with < 10 mm/sec) in the earlier study. Little agreement exists about the effect of cutting edge angle (A) on force and energy requirements. Kempe (1967) reported that a 45 o cutting edge angle require 20 to 30% less force to shear spruce logs than what was needed with a 60 o angle. Mattson and Sturos (1996) found that reducing the cutting edge angle (A) from 45 o to 30º resulted in a 55% reduction in peak force necessary for shearing sugar maple branches. Koch (1971) reported that a 9.5 mm thick blade with a 22.5 o cutting edge required 45% less total energy and 25% less peak force for shearing 130 mm diameter Southern Pine logs than was required when using a 45 o cutting edge (A). The counteredge angle has also been shown to affect peak force requirements. Chancellor (1957) stated that a "fine" counteredge requires approximately 25% less force than a "blunt" counteredge. Kempe (1967) reported that knives with recessed sides required 20% less peak force for the same cutting edge angle and thickness than parallel-sided knives. Koch (1971) found that tapered knives with a thin root also required less force. Koch (1971) and Johnston (1968b) both commented that small reductions in the necessary force could be achieved if the friction co-efficient between the blade and the wood was lowered. Greasing the blade has been found to have no appreciable effect but teflon coating of the blade surface is effective. The manner in which the force is applied has also been shown to have an effect. Mattson and Sturos (1996) demonstrated that an oblique cutting angle (β) requires greater peak force. They also examined the effect of cutting speed (600 vs 1100 mm/sec) on required force but found no significant difference at these high speeds. In summary, there performance may possibly be improved by tuning such design features as knife thickness, cutting edge angle (A), knife shape, knife friction, oblique cutting angle (13) and counteredge angle. Total energy and peak force required for cutting radiate pine and Douglas-fir branches were measured. Branch sizes ranged from 9 to 65 mm. Under one set of standard conditions some shears required over 50% more energy and peak force than others. Douglas-fir required more energy and force than radiate pine. Total energy and force requirements tend to increase with cutting edge angle and with blade thickness (Crossland et al., 1997). The selection of pruner machine is also dependent on type of orchard. In general intensive/high density orchards (HD system) are characterized by densities between 250 and 700 trees per ha, super-high-density systems (SHD system) orchards can present densities over 1500 trees/ha (the hedgerow system). The average full yield in high density systems ranges between 6000-10000 kg/ha for rainfed and irrigated orchards. However the economic life of the SHD is shorter (around 15 years, while in intensive system it can be more than 30 years) due to the lack of space and the competition among trees for light and ventilation inside the canopies (Freixa et al., 2011). Intensive tree orchard with narrow tree canopy or even 2D planar fruiting wall would be suitable for fully autonomous pruning system in the future. With the adoption of intensive tree architecture as well as the improvement of cutting end-effector, tree branch identification and reconstruction, it is very promising to have a robotic pruning system for tree fruit crops (He & Schupp, 2018). A remote operated system may be an operating alternative for pruning equipment although there are remote control systems developed in the United States, Canada and Israel (Castellanos et al., 2017). A study was done to determine the input requirements for both the hydraulic circuit and the mechanical pruner designs. Then a description of an adapted inter-axle carrier used for the experimental model of the hop mechanical pruner and of the effected field measurement follows, along with interpretation of the measured data. These data are depicted in clearly arranged graphs showing the dependency of pressure and hydraulic oil flow on the cutting disc rotational frequency (Hoffmann et al., 2015).

Econom
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Results
Field eval orchard sp   The time i pruning tim number of   The saving of time for pre-pruner as compared to manual pruning varied between 99.32-99.38%. For side pruning two sides were considered and for top pruning only one side was considered. The time for turning of pre-pruner was measured as 60 seconds and was added in both times involved in side pruning and top pruning. The effect of pre-pruner and manual pruning on pruning time per tree and pruning time per acre are shown in Table 5 and results of statistical analysis are shown in Table 6. The data for time involved in top pruning of tree is shown in Table 7. The effect of pruning method was significant on time involved in side pruning per tree and per acre (p < 0.05). Some authors, such as Kallsen (2005), compared several types and intensities of mechanical pruning, such as topping at several heights and some hand-pruning intensities, with non-pruning. He noticed that, in all cases, the higher the pruning intensity was, the lower the yield was, regardless of the type of pruning used.
In the same way, Joubert et al. (2000), working in South Africa, tested the effect of light and severe prepruning followed up by hand pruning in 'Valencia'and 'Navel' oranges and 'Star Ruby' grapefruits. After three years'experimentation, they were able to confirm that all the systems tested produced a higher yield than the unpruned control, with the best choice being hedging with an inclination of 10-20° combined with hand pruning once or twice a year. Pre-pruning in which a tilted plane is produced facilitates lighting of the bottom of the tree and also favours the concentration of fruits in the lower part of the tree, which makes manual harvesting easier. Spanish citrus farmers like to leave the trees with large skirts because this is a highly productive part of the tree. However, skirting tests performed with prepruners have shown that the overall production of the tree is not affected, while mechanical harvesting is facilitated, problems with soil fungus are reduced and tree microclimate is affected (El-Zeftawi, 1976;Morales et al., 2000;Sauls, 2008). Nowadays, mechanical pruning, either alone or combined with hand pruning, is used by some Spanish farmers. It is, however, not a technique that is widely accepted by growers, among other reasons due to a lack of experience. Pruning citrus trees must be a general canopy management strategy based on the understanding of specific pruning and regrowth management practices that must be combined with cost-effective methods adapted to each orchard period, growth, full production and old trees decline due to age and/or shading (A. J. Krajewski & S. A. Krajewski, 2011). So economics part was also calculated for the pre-pruner operation keeping in view its future scope.

Economics
The economics calculation was also done for pre-pruner and manual pruning method. The operational cost for pre-pruner and manual pre-pruner were calculated taking into account their field capacities. The field capacity was calculated using all the time involved in pruning jas.ccsenet.org Journal of Agricultural Science Vol. 13, No. 4;2021 Figure 12. A graphical representation of field capacity and cost of pruning operation for pre-pruner and manual pruning operation for manual method For pre-pruner machine time lost in turnings, breakdowns etc were taken into account. The labour cost (0.61 €/h), diesel cost (0.79 €/L), repair costs were considered for calculations. The cost of operation for side pruning operation for pre-pruner and manual pruning were calculated as 2.38 €/ha and 336.11 €/ha respectively ( Figure  12; 1 € = 82.19 INR). The cost of top pruning for manual method was not worked out as it was not possible for this method. The cost of top pruning in case of pre-pruner was worked out as 1.36 €/ha. The saving in cost with pre-pruner machine for side pruning was 99.29% with added advantage of complete top pruning of tall fruit plants/orchards.

Conclusions
The mean field capacity of manual pruning was calculated as 0.002 ha h -1 for side pruning and for top pruning the manual efficiency was very low and unable to complete the pruning due to reach problem. Whereas in case of tractor operated pre-pruner the mean field capacity was higher for side and top pruning as 0.587 ha h -1 and 1.030 ha h -1 respectively along with benefits of efficient and complete pruning. Orchard planting geometry should be such as to facilitate easy, quick and balanced movement of tractor in between rows and at headlands, i.e., orchards should have minimum of ridges, undulation as well as weeds/grasses to avoid slippage of tractor during operation and for maximizing field capacity of machine. The irrigation planning of orchard should be done keeping in view the date of next pruning operation or should be well in advance before pruning operation so that during pruning field is in dry conditions this so to provide good traction condition for tractor during operation. The operator should be fully aware about controls of pre pruning machine and equipped with good driving skills which are very important for field operation and road movement of pre pruning machine.
Tractor with cabin should be preferred for pre pruning machine for safety of operator as during pruning of trees small wooden pieces may hit and cause injury to the tractor operator. For plants having height more than 10 feet high clearance tractor may be used for enhancing visibility of operator during field operation. The pruning of tree sides should be done before start of top pruning. The choking may occur in pre pruning machine for the case when machine is lowered to increase cutting height of top portion greater than overall height of cutting unit. Therefore cutting height for top portion should be selected accordingly.

Before Starting Operation Operator Should Check These Points Daily
 The oil level in the reservoir should be checked for marked level and if found less should be filled up to marked level first.
 Nuts of all the rotating blades and other units should be checked and tightened if needed.
 The free movement of pre pruning machine should be checked in all planes.
 The rotary blades should be checked by running them ideally.
 All the hose pipes should be checked for any leakage and if found should be repaired or replaced before operation.  Vol. 13, No. 4;2021  The support system of should be checked thoroughly for any loose nuts and if found any should be tightened.
 The wearing of cutting discs also depend on the branches diameter but normally they need sharpening before starting a new season.