Abstract: Land degradation as well as agriculture production under scarce water conditions are vital concerns for many countries located in arid regions. The aim was to introduce, test and optimize a new mechanized transplanting technique suitable for large-scale establishment of fodder shrubs under Water Harvesting (WH) micro-catchment systems. A traditional transplanter was modified to plant 1 to 2-month old Atriplex seedlings inside the WH structures. The optimum time of planting (T1, T2 and T3), the optimum harvested water regime (4, 8 and 12 m) and the placement of transplants (V1 and V2) were investigated. Survival percentage throughout the two dry years and plant volume at the end of each year were assessed. In the first year, T2 resulted in the highest (80% with lSD = 30 at p<0.05) survival percentages, while T3 showed the least (75 cm3 with lSD = 403 at p<0.05) plant volume. However, in the second year, no drop in survival percentage was observed in T1, resulting in the best plant volume (652 cm3 with lSD = 282 at p<0.05). On the other hand, plant volume in V2 was double (603 cm3 with lSD = 174 at p<0.05) than that of V1, justifying its adoption. No significant effect of the length of the runoff area was noted in the two years due mostly to low quantity and intensity of rainfall events. Survival of Atriplex under WH systems is critical only in the first year of establishment and earlier planting guarantees better production. The new technique proved to substitute the costly and time-consuming traditional manual one. Further improvements are still viable.
INTRODUCTION
Efforts have been made, in the last decades, by many research and development projects in the East Mediterranean arid steppe to utilize the limited amount of rainfall, aiming at revegetation abandoned rural areas and slowing the degradation process.
To achieve these purposes, Water-harvesting (WH) systems were suggested and introduced by many researchers (Boers and Ben-Asher, 1982; Armitage, 1985; Bruins et al., 1986; Reige et al., 1988; Critchley and Seigert, 1991; Oweis et al., 2001; Prinz, 2001) as an important option. In such systems, rain water for supporting plant growth is collected in micro-catchments through the runoff from specific area.
Techniques included constructing WH micro-catchment of different shapes, sizes and with various runoff areas. The most popular of them were the continuous and discontinuous contour furrow/ridges, where drought and salt tolerant forage shrubs have been successfully established. Atriplex spp., being most potential and common species, was suggested by many researchers (Osman and Ghassali, 1997; Hopkins and Nicholson, 1999; Aganga et al., 2003) for degraded arid rangelands.
Despite the positive outcomes achieved, the establishment of forage shrubs under those systems encountered different problems that were not sufficiently studied. For example, plant establishment from seed was unsuccessful due to either emergence failure caused by strong crusting, or severe dry conditions prevailing after emergence of young seedlings (Abu-Zanat, 1995; Hatten and Taimeh, 2001). Abbad et al. (2004a) and Haddioui et al. (2008) attributed germination inhibition of Atriplex seeds to the saline medium.
On the other hand, forage shrubs establishment in the Badia succeeded only if older than six-month bag-grown transplants were used (Sankary, 1986; Jasra et al., 2007). However, their use increased the cost of nursery, transport and field preparation, where plenty of time and labor were consumed. According to Abu-Zanat (1995), labor comprised 3-50% and seedlings 50- 60% of the establishment cost. Additionally, there was a need for supplemental irrigation to support transplants survival, if the first effective rain was delayed (Oweis and Hachum, 2006).
The lack of specialized (unconventional) machinery that supports the implementation of WH and plant establishment techniques (catchment opening, transplanting or seeding) made the large-scale implementation in the Badia tedious, slow and costly. Al-Tabini et al. (2008) reported that lack of mechanized power limited the establishment of WH systems to small-scale projects.
Special machines have been developed for range vegetation programs in Australia (Gintzburger and Skinner, 1985). Unfortunately, most of these machines were developed for direct seeding in areas of higher than 200 mm annual rainfall (Hill, 1987) and for soil and climate conditions that differ from those prevailing in the Badia or similar degraded regions with less precipitation.
One of the successful attempts to introduce a mechanized furrow-opening technique to the Badia region in Syria and Jordan was the use of Vallerani machine (named after its inventor). This machine prepared and worked the land so that the rainwater was harvested in either half-moon micro-basins (intermittent contour furrow\ridges) or in continuous ones. The average field capacity of the Vallerani furrow opener ranged between one and two hectares per hour (Prinz, 1994, 2001; Malagnoux, 2006) as compared to no more than one hectare per day if conventional plows and intensive labor were used (Antinori and Vallerani, 1994). With such high capacity of the Vallerani machine, any non-mechanized operation to complete establishing the system, such as transplanting or drilling, was considered a bottle neck in the overall rehabilitation process (Antinori and Vallerani, 1994). Using conventional transplanters was, as Gammoh (2011) noted, impractical due to the bulky size of the transplants' bags and to the unleveled profile of the micro-catchments, over which the machine should run (Bailey et al., 2009).
The first specific objective of this research work was to substitute the non-mechanized laborious technique of establishing 6 month old Atriplex plants, inside the WH micro catchments, by a mechanized technique that uses 1 to 2 month old seedlings instead.
The second specific objective was to investigate and optimize the best conditions, under which the new transplanting technique is expected to be most successful. Those conditions included time of transplanting, placement of the seedling inside the WH micro-catchment and the supporting water regime which is affected by the length of runoff area between subsequent furrows.
This work aimed at introducing and optimizing a mechanized transplanting technique to the WH systems in order to reduce the cost and time of fodder shrubs establishment. In addition, improving the overall system capacity by making the large-scale implementation more feasible was targeted.
MATERIALS AND METHODS
In a study from September 2006 to November 2008, the establishment of less than 2 months old forage shrub (Atriplex nummularia) and the optimum conditions for such establishment were investigated. A traditional transplanter was modified and tested to suit the application of Atriplex transplanting inside the furrow/ ridge micro-catchment. The target was to modify the transplanter unit so it can plant 1-2 month old Atriplex seedlings, then to attach this unit to a furrow opener so that the opening of the furrow and the seedlings transplanting were performed in one pass of the tractor.
Transplanter modification: A universal mounted transplanter (manufactured by NARDI S.p.a, Italy, model TUF) illustrated in Fig. 1a) was modified (Fig. 1b) so it can perform the transplanting inside the WH structure instead of flat ground.
The modifications made to the transplanter included:
| • | Replacement of the slot opening device 1 (Fig. 1a) with a new locally fabricated one 1' (Fig. 1b) that can work deeper than the ground wheel 2 adjustment permits. This was made as the slot has to be opened in the inclined ridge of the micro-catchment at a level lower than natural ground |
| • | Addition of protecting boards 3 (Fig. 1b) to the slot opener in order to support the ridge and to prevent loose soil from heaping down from the ridge over the seedling before the last rests inside the slot |
| • | Addition of a disc type covering device 4 (Fig. 1b) to improve the coverage of seedling roots. The covering disc was mounted on the frame 5 (Fig. 1b), with minimum possible distance between it and the slot opener |
| • | Replacement of the support brackets 6 of the depth control spindle 7 (Fig. 1a) by new fabricated brackets 6' (Fig. 1b). This expanded the ground wheel adjustment range so it can be raised higher which allowed the unit to go lower into the micro-catchment |
| • | Removal of the right wheel of the pressing wheels 8 (Fig. 1a) from the transplanting unit |
| • | Alteration of the tilt angle of the remaining left press wheel 8' and the replacement of its leg 9 (Fig. 1b) with a longer one 9', to enable farther reach of the wheel to contact the lower side of the ridge |
| • | Replacement of the hitching system (the tool bar 10 and mounting brackets 11) of the transplanter (Fig. 1a) with a regular square-section tool bar 10' and new brackets 11' with clamps 12 (Fig. 1b). This allowed attaching the transplanting unit to a regular furrow opener |
Field experiment: Three groups of Atriplex nummularia seedlings (350 seedlings each) were grown from seeds at three different dates in specially fabricated trays of 100 cubic (4x4x4 cm) pots.
| Fig. 1: | (a) Side (left) and front (right) views of universal mounted transplanter (manufactured by NARDI, Italy) and (b) The same transplanter views after modification. Components: 1-slot opening device, 2-ground (or depth) wheel, 3-protecting boards, 4-covering disc, 5-frame, 6-support brackets, 7-spindle, 8-pressing wheels, 9-leg, 10-tool bar, 11-mounting brackets, 12-bolt clamps, 13-feeding unit, 14-worker seat |
Accordingly, the age of each group at the moment of transplanting in the field was 1-2 months.
The modified transplanter was attached to a disc-type furrow opener. This integrated unit was used to open WH micro-catchments and to transplant them with Atriplex seedlings in one pass of the tractor. The transplanter was calibrated to eject one seedling per meter along the micro-catchments either in the bottom of the micro-catchment, or on the lower 1/3 part of the ridge. The WH micro-catchments were continuous tied furrow/ridges, with 50 cm width and 30 cm depth furrow and 50 cm height ridge (as measured from the bottom of the furrow).
Experimental site conditions: The field experiment was carried out at the University of Jordan Research Station in Muwaqqar; 400 m ASL located 30 km southeast of Amman. The coordinates are 266°-270° East, 130°-135° North (Jordan Royal Geographic Center, plate No. NH37-A-1). The site represents the arid region of “Badia”, where annual rainfall ranges between 100 and 150 mm. The 0.8-ha experimental field was of a uniform slope (2-3%) with small variation in soil depth (90 cm uphill and 120 cm downhill).
The runoff and effective rainfall events for the two seasons were assessed by a weather station, installed 100 m from the experimental site. The total rainfalls in the first and second years were 147 and 84 mm, respectively. The rainfall events that initiated runoff in the micro-catchments summed 90 and 61 mm, respectively.
Treatments and experimental design: The main treatments reflected time of planting, where T1- transplanting before first rainfall, T2-transplanting few days after a good runoff event and T3-transplanting in spring at the beginning of the warm growing season.
T1 was implemented on 24/12/2006 and fortunately, the first rainfall with 3.4 mm occurred two days later, followed by 27mm with good runoff on the third day. T2 was implemented on 28/1/2007 after a rainy week of 19 mm rainfall and a good runoff event on 20/1/2007. T3 was implemented on 11/3/2007. The total rainfall after this date until the end of March 2007 was 26 mm; 13 mm of them fell on 15/3/2007 which have initiated an effective runoff event.
To investigate the effect of water regime inside micro-catchments (quantity of harvested water), the main treatments plots were split according to the spacing between furrows into three sub-treatments T1, T2 and T3 with 4, 8 and 12 m length of runoff area, respectively.
To investigate the effect of seedling placement inside the micro-catchment, the sub-plots were split into two sub-sub-treatments, V1-transplanting in the bottom of the furrow closer to the ridge (wetter) and V2-transplanting above the bottom 1/3 of the ridge (less sediments). Each sub- sub plot furrow/ridge micro-catchment was 24 m in length; 12 seedlings were planted as V1 and 12 as V2. Thus, a split-split plot experimental design in four replicates was considered.
Parameters assessed: Survival percentage for the first year was assessed through survival count every month on the growing season (on 16/3, 16/4 and 16/5/2007) and twice in the dry season (on 4/7 and 9/9/2007) and was assessed three times in the second year; at the end of the rainy season (on 21/2/2008), the end of the growing season (on 8/5/2008) and at the end of the dry season (on 2/11/2008). The statistical analysis was performed for the results obtained at the end of dry seasons of the two years, on 9/9/2007 and 2/11/2008.
Plant volume was estimated through measuring the height and width of each plant at the end of the growing season for two successive years. The volume was then calculated using the mathematical equations of volume of a cylinder or a cone, depending on plant shape. Therefore the following equations were implied:
| (1) |
where, Vcyl is cylinder volume (cm3), π is 3.14, r and l-cylinder base radius and cylinder height (cm) and
| (2) |
where, Vcone is cone volume (cm3), b and a-cone base diameter and cone height (cm).
The plant volume was calculated for each survived plant then averaged for each sub-sub plot.
Statistical analysis: A split-split plot experimental design with four replicates was followed in this experiment. Statistical analysis was performed using the SAS Statistical Analysis Systems computer package. The MIXED procedure and mean separation test were employed using Least Square Differences (LSD).
RESULTS AND DISCUSSION
Survival in the first year: The average percentage of the survived plants through the growing and the following dry seasons, calculated on 9/9/2007 (Table 1) were 37, 80 and 61% under T1, T2 and T3, respectively. In the Jordanian “Badia”, Hatten and Taimeh (2001), Abu-Zanat et al. (2004) and Mudabber et al. (2008), reported 65 to 90% survival percentages of Atriplex grown from older than 6-months transplant under different water harvesting structures and varying precipitations. Therefore, the percentages obtained in this experiment, from 1-2 months old seedlings, could be acceptable for the successful establishment of Atriplex.
Although, the planting before the rainy season (T1) was expected to give the best results (Bleak et al., 1965; Sankary, 1986), it showed the least survival percentage. This could be attributed to the freeze waves that struck the young seedlings in January 2007 (minimum temperatures ranged from-2 to-4°C for 3 days from 1 to 3/1/2007 and 1 to -3°C for 8 days from 13 to 20/1/2007), when T2 and T3 were not yet implemented. The drop in survival percentage due to the freeze strike was 39.8% as counted afterward.
During the dry season, an additional 22.2% drop occurred in survival percentage under T1, summing up to 62% (Fig. 2a). Meanwhile, the greatest drop in survival percentage was 38.9% under T3 (transplanting in spring) and the least (19.8%) under T2 (transplanting in the wet time).
| Fig. 2: | Seedling survival through the dry season of the first year as affected by (a) date of planting (T1, T2 and T3) and by (b) seedling placement inside the micro-catchment (V1 and V2) |
Although these results are in agreement with Bleak et al. (1965) and Roberts and Neilson (1980), they contradict the results reported by Springfield (1976). However, the later studies were conducted in zones with annual rainfall of more than 250 mm, with better rainfall distribution and with colder winters. In the current study, it is thought that the drop under T3 could be attributed mainly to the inability of some seedlings, planted in spring, to develop roots deep enough to reach the wet zone before the top soil dried up. Thus, transplanting mid-winter after good runoff events (T2) reduced the risk of harsh “Badia” weather which is usually expected in early winter and took advantage of early developing roots deep enough before the dry season starts. Similar notes were reported in Australia with 125 mm rainfall by Wood et al. (1982) and Beadle (1952).
The survival percentage at the end of the dry season was not significantly affected at p<0.05 (Table 1) by the spacing between furrows (length of runoff area). It seems, as Gammoh (2011) and Suleman et al. (1995) reported that the furrow spacing had a significant effect on soil water storage at relatively deep layers that young seedlings’ roots had not yet reached at this stage of their growth. Moreover, it is expected that the effect of furrow spacing might be significant under higher intensities of rainfall events and steeper slopes which can initiate greater runoff and consequently affect the water availability inside the WH micro-catchments.
| Fig. 3: | Plants survival through the dry season of the second year affected by date of planting |
Mudabber et al. (2008) reported significant effect of furrows' spacing on Atriplex survival percentages in “Badia” in seasons with higher annual rainfall and higher intensities events.
The seedling placement inside the micro-catchment had no significant effect (at p<0.05) on the survival percentage at the end of the dry season (Table 1). Nevertheless, it was noticed, while counting survival, that when drought stress increased from June to September, the drop in survival percentage for V2 and V1 were 19 and 23%, respectively (Fig. 2b) which might give a privilege for V2. Moreover, it is believed that placing the seedlings on a higher level above the bottom of the furrow (V2) provided protection for young and short seedlings used in this experiment from being flooded in case of intensive rainfalls and filling the furrow by the runoff.
Survival in the second year: The percentage of the survived plants under different treatments after the growing and dry seasons of the second year, as calculated on 2/ 11/ 2008, ranged from 41% under T1 and T3 to 58% under T2 (Table 2). If considering the very dry season (half annual rainfall of the region) and the very long period of rain absence (from February to November), these percentages can be considered more than acceptable. Ali and Yazar (2007) attributed the survival of Atriplex, established in WH micro-catchments after the second dry year, mainly to its drought tolerance. However, Oweis and Hachum (2006) and Gammoh (2011) attributed the survival of Atriplex after dry seasons to the favorable soil water regime created by the water-harvesting structures. In this study, it is believed that both reasons were effective.
The survival percentages at the beginning and the end of the dry season (Fig. 3) were compared and the percentage drops in these percentages were calculated The drop was around 28% under T2 and T3, while it was only 4.5% under T1 This emphasizes the advantage of planting early, before the rainy season, in comparison with planting in the middle of the season (T2) or in early spring (T3).
| Table 1: | Means of survival percentages in the first year under different treatments (date of transplanting), sub-treatments (spacing between furrows) and split variables (plant placement inside the WH micro-catchment) |
| LSD values for treatments, sub-treatments, sub-sub-treatments and their interaction were (30.4, 12.6, 7.7) and (32), respectively at p<0.05. Letters of significancy in lower case are for the interaction and upper case for treatment | |
| Table 2: | Means of survival percentage in the second year under different treatments, sub-treatments and sub-sub-treatments |
| LSD values for treatments, sub-treatments, sub-sub-treatments and their interaction were (33.6, 15.9, 8.5) and (37.5), respectively at p<0.05. Letters of significancy in lower case are for the interaction and uper case for treatment | |
| Table 3: | Means of plant volume in cm3 for the first year under different treatments (date of transplanting), sub-treatments (spacing between furrows) and sub-sub-treatments (plant placement inside the WH micro-catchment) |
| LSD values for treatments, sub-treatments, sub-sub-treatments and their interaction were (403.1, 271.6, 216.6) and (649.7), respectively at p<0.05. Letters of significancy in lower case are for the interaction and uper case for treatment | |
The survival percentages of established plants after the second season (Table 2) were not, in general, clearly affected by the date of plant establishment, by the spacing between furrows (length of the runoff area), or by the placement of plants inside the furrow. It is believed that the expected significancy was masked by the low annual rainfall amount (half annual average) and by the effect of severe and prolonged hot weather through 2008. If comparing with survival percentages from the first year, there was a drop of 27 and 30% under T2 and T3, respectively, while the well-established plants under T1 were not affected. A slight increase in the survival percentage under T1 was observed in the second year. This might be attributed to the ability of some plants (that were counted as dead in the first year) to regenerate new shoots when conditions were suitable for growth.
Plant volume in the first year: As Table 3 shows, planting before the first rainfall (T1) and in mid season (T2) proved to have significantly better effect on plants growth (at p<0.05 with lSD = 403) than planting late in spring (T3). Although the survival rate under T1 was less than that under T2 (Table 1), the survived plants, planted one month before, seemed to have benefited from the rainfall between the two dates of planting and have developed deeper rooting.
Average plant volume under T3 was significantly (p<0.05) the lowest (8-fold less than under T1), although, the plants survival percentage in the first season was better than that under T1 (Table 1). This can be attributed to the fact that the transplants could not develop their roots deep enough to reach the wet soil layers before drying of the top soil which has affected their growth and productivity.
No significant effect (at p<0.05 with lSD = 272)) of the length of runoff area (T1 = 4 m, T2 = 8 m, T3 = 12 m) on the averaged plant volume was noticed (Table 3).
| Table 4: | Means of plant volume in cm3 for the second year under different treatments, sub-treatments and sub-sub-treatments |
| Note: LSD values for treatments, sub-treatments , sub-sub-treatments and their interaction were (281.9), (217.6), (173.5) and (527.7), respectively at p<0.05. Letters of significancy in lower case are for the interaction and uper case for treatment | |
In the Badia, with similar micro-catchments and spacing, Hatten and Taimeh, 2001 noted proportional increases in dry matter production per plant between 4 and 12 m spacing. However, their experiment were carried out under different slopes and rainfall intensities. Therefore, it is believed that the difference in water volume, harvested from different runoff areas, is expected to have significant effect on water regime inside the micro-catchment under higher rainfall intensities and steeper slopes.
The effect of plant placement inside the catchment (V1 and V2) on the average plant volume was obviously significant (at p<0.05 and lSD = 217). It was nearly twice greater under V2 than that under V1 (Table 3). This can be attributed to the looser soil and deeper root development in the root zone under V2. Moreover, it is believed that placing the young plants inside the ridge (V2) provided them with better protection from sun radiation and wind in hot summer than placing them in the open bottom of the furrow (V1).
Plant volume in the second year: The second year results seem to have been similar to those in the first year. In particular, the effect of treatments (dates of transplanting) and the effect of plant placement on the average plant volume were significant at p<0.05, while that of furrows' spacing was not (Table 4). In wetter zones, Mahdavi et al. (2009) noted 2 m spacing between Atriplex rows better than 4 and 6 m ones to give higher biomass weight.
A comparison of the results of the two years showed that the effect of drought on the plants in the second year is clearly seen in the small increase in their volume. It is thought that the little precipitation in the dry year have increased salt stresses which might, as to Abbad et al. (2004b) have induced a reduction in the biomass production.
The average plant volumes at the end of the two years, presented in Table 3 and 4, were compared and the increase percentages in these volumes were calculated. There were, respectively, 5, 19 and 78% increase under T1, T2 and T3; 11, 20 and 14 under T1, T2 and T3 and 21 and 12% under V1 and V2. The highest increase under T3 can be explained by their relatively small initial volume at the beginning of the second season. Provided that the seedlings have survived the first year, those growth results highlighted the capacity of WH systems to help the plants replenish their growth even in dry seasons.
CONCLUSIONS
Transplanting young seedlings (1-2 months old) proved to be a successful mechanized practice under water harvesting systems for the establishment of forage shrubs in the marginal dry rangelands of “Badia”. The benefits are reduced time and cost at the nursery stage, easier handling and higher field capacity than the traditional practices.
Atriplex, in the first year of establishment, can benefit more if planted early in the rainy season. However, there is a high risk (in the first year only) of adverse effect on the survival of the prone young seedlings in harsh weather conditions and in the event of rainfall delay. Transplanting in mid wet season reduces the mentioned risk and improves survival percentage, while planting in early spring is not favored if good rainfall events afterward are unlikely. It is recommended to change the common practice of placing the shrubs in the bottom of the micro-catchment furrow and plant them in the lower half of the ridge. In water harvesting systems, the spacing between furrows should be considered under conditions of steep lands and intense rainfall events. To achieve improved performance, further work in the construction and design of machinery is still needed.
ACKNOWLEDGMENTS
This research work was supported and funded cooperatively by The University of Jordan and The International Centre of Agricultural Research in the Dry Areas (ICARDA). I thank Osama Abu Sheikha for his continuous help in the mechanical works at the workshop and on the field, Dr. Najib Al-Asi for his constructive comments on the manuscript and Dr. Muhannad Al-Akash for his help in statistical analysis of the results.