INTRODUCTION
There is a need for efficient application of nitrogenous fertilizer as mismanagement
could lead to leaching and contamination of surface and ground water sources
as well as soil degradation. Nitrogen is amongst the most important nutritional
element in garlic and other crops and actively acts in numerous metabolic processes.
The nitrogen content is directly related to the synthesis of proteins and carotenoids
and would affect garlic fruit coloration and different plant organs at the skin
as well as the bulb level (Romojaro et al., 2007).
Application of nitrogen fertilizer lead to mineralization and nitrification
process that converts the organic N and NH4+ into NH4+
and NO32¯, respectively which are absorbed and utilized
by crops and termed as available nitrogen. Microirrigation (drip and microsprinkler
irrigation system) has the potential for precisely applying water and fertilizers
throughout a field both in terms of amount and location. This potential can
results in higher yield, water and fertilizer saving and can also reduce leaching
of nitrogen to the ground water (Tripathi et al.,
2010). Various studies suggested that ground water pollution due to nitrate
leaching is becoming a serious problem in India, particularly in agriculturally
developed states such as Punjab, Haryana, Andhra Pradesh and Maharashtra, where
fertilizer applications are high. Fertigation is the process of applying soluble
fertilizer along with irrigation water. Fertigation is an efficient means of
applying crop nutrients, particularly nitrogen and it may results in reduction
of application of nitrogen fertilizers. Nutrients applied through fertigation
can be applied directly to the wetted volume of soil where the majority of roots
are located and therefore nutrient use efficiency by the crop can be increased
and the leaching potential of mobile nutrients can be decreased (Thorburn
et al., 2003). Smika and Watts (1978) studied
residual NO3¯-N in fine sand as influenced by nitrogen fertilizers
and water management practices. They found that at lower application rates residual
NO3¯-N was very low because it was nearly equal to plant uptake.
They also concluded that the injected N application method with the proper water
application management can greatly reduce the potential for NO3¯-N
movement below the crop root zone in fine sandy soils.
Improved understanding of solute dynamics in the crop root zone should help
to improve fertigation schedules for better microirrigation management (Mmolawa
and Or, 2000). Instead of giving the recommended fertilizer in one dose,
split application is appropriate method in fertigation as the nitrogen is most
vulnerable to the leaching (Darwish et al., 2003;
Haynes, 1990). When N is used for crop production in
sandy soils, method and time of application are of equal importance because
of the potential for leaching losses of NO3¯-N through these
soils during the growing season (Wolkowski et al.,
1995). The amount of N available for leaching and NO3¯-N
leached beyond the root zone were affected by amounts of N fertilizer, the amounts
of irrigation water and amounts of annual precipitation (Ersahin
and Karaman, 2001). Therefore, careful management practices are required
on particular soil in specific place.
Microirrigation system can be designed and operated such a way that water and
nutrients are applied at particular rate, duration and frequency, so as to maximize
crop water and nutrients utilization from the root zone of agricultural fields.
After irrigation both soil moisture content and nitrogen concentration will
be higher near the microirrigation application point but will redistribute thereafter
as controlled by soil physical properties because of non-uniform wetting patterns
of soil. However, it is possible that percolation of irrigation water below
the root zone and nitrate leaching occurs despite that applied irrigation water
is equal or less than crop evapotranspiration. Pawar et
al. (1998) opined that microsprinkler method is suitable for irrigating
close growing crops like garlic by closely spaced microsprinklers in terms of
soil water distribution. However, the distribution of point source application
of water and fertilizer would be different than the disc source of application
as in the of case of microsprinkler system. The difference of water and nitrogen
distribution in both (drip and microsprinkler) the method of irrigation will
vary based on the soil type. The N uptake decreased and nitrogen volatilization
and final soil nitrogen increased for the deficit irrigation treatments as compared
to the full irrigation treatments in sprinkler. Therefore, in order to avoid
nitrogen loss, the amount of nitrogen fertilizer application should be reduced
in proportion to the severity of the existing water stress condition (Gheysari
et al., 2007).
Li et al. (2008) studied water and nitrogen
distribution for summer maize under subsurface drip irrigation and reported
that the initial nitrate content in sandy loam was significantly affected on
the vertical distribution of nitrate following a fertigation event. The same
study also revealed that the nonuniform distribution of water and nitrogen in
the soil following a fertigation event was mainly caused by the spatial variation
of soil properties, especially the initial distribution of soil water and nitrogen
contents. The mobility of applied N through the drip irrigation system depends
on the form (granular or powder) in which it is presented (Haynes,
1990). It has been reported that movement and transformations of fertigated
urea were influenced significantly by the time of fertigation application in
an irrigation cycle (Hou et al., 2003).
Li et al. (2003) also studied influence of point
source fertigation on water and nitrogen distribution in loam soil in China.
They found that the effects of application rate and applied volume on nitrate
distribution were not significant upto a radius of 15 cm, beyond which either
a higher application rate or a smaller applied volume resulted in a higher nitrate
concentration in the soil. Measurement of ammonium distribution revealed that
an extremely high ammonium concentration in the proximity of the point source
(about 2.5-7.5 cm from the source). The value of the peak ammonium concentration
greatly depended on the input concentration. An increased input concentration
produced a higher ammonium concentration around the point source.
Nitrate distribution in the soil for various fertigation strategies, soil types
and methods of microirrigation was evaluated by Blaine et
al. (2004). They found that injecting NO3¯ for a few
hours at the beginning of an irrigation event could result in relatively nonuniform
distributions of fertilizer in the root zone and may leach most of the NO3¯
beyond the root zone. On the other hand, injecting for several hours at the
end of the irrigation event could result in most of the NO3¯
remaining near the drip line. Therefore, the timing of fertigation relative
to the start and end of the irrigation event coupled with duration of fertigation
event can affect crop NO3 availability and leaching.
Very little information is available for water and nitrogen movements under
microirrigation fertigation in garlic crop. There is a need to develop information
based on water and nitrogen dynamics in the root zone for garlic crop to develop
best fertigation design and management guidelines. This study was planned to
develop database on water and nitrogen dynamics in garlic crop under microirrigation
fertigation in order to develop design and management guidelines for microirrigation
(drip and microsprinkler) fertigation.
MATERIALS AND METHODS
Field experiments were conducted on garlic (var., Yamuna safed) crop
under microirrigation (drip and microsprinkler) fertigation on the farm of the
Indian Agricultural Research Institute (IARI), New Delhi located between the
latitudes of 28°37’22”
N and 28°39’ N and longitudes
of 77°8’45”
E and 77°10’24”
E at an average elevation of 230 m above mean sea level. Climate of New Delhi
is categorized as semi-arid, subtropical with hot dry summer and cold winter.
The mean annual rainfall is 710 mm of which as much as 75% is received during
monsoon season (June to September). Some winter showers are also received during
December and March. Frost occurs occasionally during the months of December-January.
Experiments were carried out in the garlic crop growing season of the years
of 2008-09 and 2009-10.
Randomized block design was used with four levels of fertilizers treatments
with three replications in drip and microsprinkler method of irrigation. The
plot size was kept as 3x4 m. The fertilizer treatment imposed were N0 (0 kg
ha-1), N40 (40 kg ha-1), N80 (80 kg ha-1),
N120 (120 kg ha-1).
| Table 1: |
Treatments details |
 |
The field experiments consisted of design and installation of microirrigation
fertigation system, field observations, samplings and analysis of soil and plant
samples. Drip laterals were placed in the middle of the rows and spaced at 0.6
m to cover the two rows of the crop. Crop row to row spacing and plant to plant
spacing was kept as 15 and 10 cm, respectively. Drip emitters were placed on
the lateral line at a spacing of 50 cm. Two microsprinklers were placed in each
plot with the spacing of 2 m. The drip and microsprinkler systems were operated
for each treatment in all the replications at the same time. The details of
experimental treatments were given in the Table 1.
Irrigation and fertigation schedule: Water requirement of garlic crop
was estimated using the Penman-Monteith method. Previous five years (2002-2005)
average daily reference evapotranspiration (ETo) values were multiplied
with the crop coefficients to estimate the daily crop water requirements of
garlic crop. Irrigation requirement was estimated by subtracting corresponding
rainfall during the crop season. Nitrogen fertilizer in the form of urea was
applied with the interval of once in twenty days in four equal split doses.
During each fertigation application, fertilizer was applied in the beginning
of irrigation for 0.17 h. The amount of nitrogen fertilizer applied per dose
was 150, 313 and 470 g in N40, N80 and N120 levels of nitrogen, respectively.
Apart from nitrogen fertilizer, the recommended doses of P (50 kg ha-1)
and K (50 kg ha-1) were applied after sowing as basal application.
Field observations and laboratory analysis: Soil samples were collected
from different depths (0-0.15, 0.15-0.30 and 0.3-0.45 m) at emitter, 12.5 and
25 cm away from emitter along the lateral and 15 and 30 cm across the lateral
periodically (before fertigation and 24, 48, 72 h after fertigation) in drip
irrigation. In microsprinkler system soil samples were collected at 50, 100
and 150 cm away from the microsprinkler head along the lateral as well as across
the lateral for three soil depths. Tube auger was used for collecting soil samples
from the experimental area to determine spatial and temporal distribution of
water and available nitrogen during the growing season. The soil samples were
collected after each fertigation in both the methods of irrigation. These samples
were analyzed to determine the gravimetric water content and available nitrogen.
Kjeldahl method (Page et al., 1982) was used to
estimate the ammonium and nitrate forms of the available nitrogen. In this method,
distillation procedures for determination of NH4+ and
NO3¯ involve steam distillation with MgO and Devarda alloy.
Soil samples were shaken with 2 M KCl (10 mg g-1 of soil ) for 1
h and the extract liberated by steam distillation was collected in H3BO3¯
indicator solution and determined by titration with standard (0.01 N) HCl. The
plant samples were collected in all the treatments at the time of harvest. Water
is removed from plant tissue to stop enzymatic reactions and to stabilize the
sample. Removal of combined water also facilitates particle size reduction,
homogenization and weighing. The plant samples were digested in the KEL PLUS
digester block. Total nitrogen of the plant samples were determined by Kjeldahl
method (Page et al., 1982).
RESULTS AND DISCUSSION
Water distribution in drip fertigation: The results of soil water content
distribution in drip irrigation are presented in order of along and across the
lateral in both the seasons. As the plant entered into the development stage
(35 DAS) after two months, the root activity during this period will be more
for uptake of water and nitrogen (Mohammad and Zuraiqi,
2003). So, the soil water distribution at 48 Days After Sowing (DAS) was
taken for the discussion. Second dose of fertigation was completed at that time.
Field capacity of various layers of the soil of experimental site was in the
range of 20-27%. Soil moisture distribution pattern at 24, 48 and 72 h after
fertigation along the lateral are presented in Fig. 1 and
2 in both the years for three places (at emitter, 12.5 and
15 cm from emitter). These figures revealed that 24 h after fertigation in the
year 2008-2009 along the lateral soil water content in the vertical plane at
emitter, 12.5 and 25 cm from emitter were 17.7-20.1, 16.5-19.5 and 14.1-18.2%.
The figures also show that the variation in soil water content at various points
in the first two layers (0-15 and 15-30 cm) was not much (1.3%). Similarly,
water content in 48 and 72 h after fertigation in these layers varied from 12.1-17.2,
12.2-16.2 and 11.9-13.5%, respectively at emitter, 12.5 and 25 cm away from
emitter. In contrary to these results Arulkar et al.
(2008) reported that with increase in water application, the water content
of soil increased horizontally and vertically in sandy loam soil. In this study,
soil water content was relatively higher in upper profile (0-30 cm) and near
the emitter in all the 3 cases after irrigation (24, 48, 72 h after fertigation)
because of redistribution. Water content in all the soil layers decreased as
the distance from the emitter with increase in the horizontal direction. Similar
results were also reported by Chakraborty (1997) and
Ajdary et al. (2007) in sandy loam soil.
Highest soil water content was observed at 24 h after fertigation in 12.5 cm
along and 15 cm across the lateral in the soil layer of 0-15 cm. While highest
soil water content was observed at 48 h after fertigation in 25 cm along and
30 cm across the lateral in 15-30 cm soil layer. Similarly, 72 h after fertigation,
highest water content was observed in above said place (25 and 30 cm across
the lateral) and layer (15-30 cm) as 48 h after fertigation. The results indicate
that due to the redistribution, soil water content reached upto the 30 cm in
horizontal as well as in vertical directions beyond emitter.
|
| Fig. 1(a-c): |
Water distribution pattern along the lateral under drip irrigation
at two months after sowing in 2008-2009 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 2(a-c): |
Water distribution pattern along the lateral under drip irrigation
at two months after sowing in 2009-2010 at (a) 24, (b) 48 and (c) 72 h |
Similar results were reported by Singandhupe et al.
(2003) with clay loam soil. The soil water content in the root zone for
garlic crop in medium textured soil should be maintained between 15-20% (Arulkar
et al., 2008). The observations of present study also indicated that
favorable water content was maintained in the root zone even after 72 h of irrigation.
This concludes that lateral spacing could be taken as 60 cm for garlic crop
under sandy loam soils.
Soil water distribution in microsprinkler: The results of soil water
content in microsprinkler fertigation plots are presented in the order of along
and across the lateral of microsprinkler in both the years. The water distribution
along the lateral in three layers (0-15, 15-30, 30-45 cm), four places (at microsprinkler
head, 50, 100 and 150 cm from microsprinkler head) and three times (24, 48 and
72 h after fertigation) are shown in the Fig. 3 and 4.
It was observed that the water content at 24 h after irrigation was in the range
of 11-17% in the year 2008-09 and 15-26% in the year 2009-2010, respectively.
While at 48 h after irrigation, the water content ranged from 11-15% in the
year 2008-2009 and 15-25% in the year 2009-2010, respectively. After 72 h of
irrigation, the water content was in the range of 10-14% in the year 2008-2009
and 12-24% in the year 2009-2010. Figure 5 and 6
show the water distribution in microsprinkler across the lateral in three layers
(0-15, 15-30, 30-45 cm), four places (at microsprinkler head, 50, 100 and 150
cm from microsprinkler head) and three times (24, 48 and 72 h after fertigation).
The water content at 24 h after fertigation was observed in the range of 10-17%
in the year 2008-2009 and 12-20% in the year 2009-2010, respectively. The water
content at 48 h after irrigation was observed in the range of 10-15% in the
year 2008-2009 and 10-21% in the year 2009-2010, respectively. The above results
indicated that even after 72 h of irrigation favorable water content maintained
in the root zone.
|
| Fig. 3(a-c): |
Water distribution pattern across the lateral under microsprinkler
at two months after sowing in 2008-2009 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 4(a-c): |
Water distribution pattern across the lateral under microsprinkler
at two months after sowing in 2009-2010 at (a) 24, (b) 48 and (c) 72 h |
Similar results were reported by the other researchers (Patel
et al., 1996; Unlu et al., 2006)
showing that the soil water distribution decreased from the point of application
to periphery of wetted area. Comparison of the water distribution in both the
methods revealed that horizontal distribution was more in microsprinkler than
in drip irrigation. But in drip irrigation vertical distribution was more than
in microsprinkler.
Nitrogen distribution in drip irrigation during growing period: The
results of available nitrogen distribution are presented in order of along and
across lateral under drip fertigated plots of garlic crop. Available nitrogen
distribution at the end of second dose of fertigation in three soil layers (0-15,
15-30 and 30-45 cm) at 24, 48 and 72 h after fertigation and at emitter, 12.5
and 25 cm from emitter are presented in Fig. 7-10
during both the seasons.
|
| Fig. 5(a-c): |
Nitrogen distribution pattern along the lateral under drip
irrigation at two months after sowing in 2008-2009 at (a) 24, (b) 48 and
(c) 72 h |
|
| Fig. 6(a-c): |
Nitrogen distribution pattern along the lateral under drip
irrigation at two months after sowing in 2009-2010 at (a) 24, (b) 48 and
(c) 72 h |
Available nitrogen distribution along the lateral were in the range of 60-110,
70-95 and 70-96 kg ha-1 and 80-95, 80-90 and 80-100 kg ha-1,
respectively for both the year in three times (24, 48 and 72 h after fertigation).
The available N across the lateral in the range was 80-110 kg ha-1
for all three timing in both the years.
In both the seasons in the treatment N80 i.e., 80 kg N ha-1 fertigation
with drip irrigation, the maximum N content was observed as 98 kg ha-1at
24 h after fertigation in 15-30 cm layer. It decreased with an increase in soil
depth below the emitter. However, at 12.5 cm away from emitter in the 0-15 cm
soil layer the N content was maximum as 96 kg ha-1.
|
| Fig. 7(a-c): |
Nitrogen distribution pattern across the lateral under drip
irrigation at two months after sowing in 2008-2009 at (a) 24, (b) 48 and
(c) 72 h |
|
| Fig. 8(a-c): |
Nitrogen distribution pattern across the lateral under drip
irrigation at two months after sowing in 2009-2010 at (a) 24, (b) 48 and
(c) 72 h |
It decreased with increase in the depth. At 25 cm away from emitter the highest
N content was recorded in 30-45 layers as 104 kg ha-1. It was observed
that the N moves with the water downwards and most of the N molecule accumulated
in the third layer (30-45 cm) of soil. Similar result was reported by Hanson
et al. (2003) in sandy loam soil.
Similar trend was observed at 48 h after fertigation and 72 h after fertigation.
However, in 2009-10 at 24 h after fertigation, at emitter the maximum N (91
kg ha-1) content was in 0-15 cm layer as compared to other lower
layers. Due to this there might not be sufficient redistribution at this time.
At 12.5 cm away from emitter the maximum N content (89 kg ha-1) was
observed in 15-30 cm layer. Similarly for 25 cm away from emitter, 15-30 cm
soil layer recorded maximum N content (87 kg ha-1). But at 48 h after
fertigation, the trend was different from the values at 24 h after fertigation.
|
| Fig. 9(a-c): |
Nitrogen distribution pattern along the lateral in microsprinkler
at two months after sowing in 2008-2009 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 10(a-c): |
Nitrogen distribution pattern along the
lateral under microsprinkler at two months after sowing in 2009-2010 at
(a) 24, (b) 48 and (c) 72 h |
In this case, the maximum N content in all three places such as at emitter
(91 kg ha-1), 12.5 cm from the emitter (87.5 kg ha-1)
and 25 cm from the emitter (87 kg ha-1) were observed in 15-30 cm
depth layer. At 72 h after fertigation, the 0-15 cm layer observed highest N
content as 85 kg ha-1 for all three points such as at emitter 12.5
and 25 cm away from emitter. Similar trend was observed in both the year in
across the lateral in 24, 48 and 72 h after fertigation at emitter, 12.5 and
25 cm away from the emitter. Gardenas et al. (2005)
observed that fertigation at the beginning of the irrigation cycle tended to
increase seasonal nitrate leaching while fertigation events at the end of the
irrigation cycle reduced the potential for nitrate leaching. Leaching potential
increased as the difference between the extent of the wetted soil volume and
rooting zone increased. The results indicated that available nitrogen decreased
from emitter to the boundary wetting zone. That means horizontal distribution
decreased while going along and across the lateral.
In general, N concentration in active root zone (15-30 cm) in drip irrigation
varied from 79-103 kg ha-1 which was more than the initial N content
in the same layer before sowing indicating adequate nitrogen availability in
the active root zone. Similar results were reported by the Arulkar
et al. (2008).
Figure 5 and 6 illustrate the distributions
of available N in the sandy loam soil in vertical plane for the four applied
fertigation doses. Comparison of Fig. 1, 2,
11, 12 and 13, 14,
3 and 6 revealed that N moves with water
during soil water movement.
|
| Fig. 11(a-c): |
Water distribution pattern across the lateral under drip irrigation
at two months after sowing in 2008-2009 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 12(a-c): |
Water distribution pattern across the lateral under drip irrigation
at two months after sowing in 2009-2010 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 13(a-c): |
Water distribution pattern along the lateral under microsprinkler
at two months after sowing in 2008-2009 at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 14(a-c): |
Water distribution pattern along the lateral under microsprinkler
at two months after sowing in 2009-2010 at (a) 24, (b) 48 and (c) 72 h |
The accumulation of N towards the boundary of the wetted volume was observed
at 72 h after fertigation. The N availability in boundary (75, 78 and 82 kg
ha-1) was low at emitter source in all three depths (94, 97 and 110
kg ha-1). In contrary to these results in a study of the simultaneous
transport of water and chloride, reported that the apparent diffusion coefficients
of chloride are less than 0.01 cm min-1 that is slower than relative
rate of water movement. This means that once a soluble non-reactive ion like
NO3¯ begins to move with water its back diffusion is slow which
means that ion and water are closely coupled.
The amounts of N in case of N40, N80 and N120 treatments were 89, 92 and 104
kg ha-1, respectively in the 0-15 cm layer. This could be attributed
to higher water content resulting in more ammonical N in this layer. To find
out the leaching trend in the treatments, N concentration in the last layer
(30-45 cm) was compared with the 0-15 and 15-30 cm layers (Fig.
7-10). It was observed that the lowest amount of N (79
kg ha-1) in the 30-45 cm layer was in treatment N40 and the highest
amount of N (95 kg ha-1) was in treatment N120. This indicates that
the chance of more nitrogen in treatment N120 in the last layer may be due to
application of more nitrogen. Lowest amount of N content in case of N80 was
due to the fact that in this treatment only 80% of recommended dose of N was
applied. The above results indicated that nitrogen availability decreased with
increasing horizontal distance in drip fertigation. Also, it was observed that
application of more nitrogen as compared to plant requirement leads to more
leaching.
Nitrogen distribution in microsprinkler fertigation: Figure
9 and 10 show the N distribution in microsprinkler along
the lateral at four places, three depths and three occasions of observations.
The available N distribution at 24 h after fertigation was found to be in the
range of 50-150 and 120-170 kg N ha-1 in the year 2008-2009 and in
the year 2009-2010, respectively. At 48 h after fertigation the range of available
N distribution was observed as 55-170 kg N ha-1 in the year 2008-2009
and 50-150 kg N ha-1 in the year 2009-2010. At 72 h after fertigation
the available N range was observed as 100-170 kg N ha-1 in the year
2008-2009 and 100-150 kg N ha-1 in the year 2009-2010. In contrary
to drip fertigation the results indicated that the available nitrogen was increasing
with increase in time due to redistribution.
Figure 15 and 16 show the available N
distribution in microsprinkler across the lateral. At 24 h after fertigation,
the range of N was observed as 94-99 kg N ha-1 in both the years.
At 48 h after fertigation the range of N distribution was 95-105 kg N ha-1
in both the years. While at 72 h after fertigation the N distribution range
was 91-107 kg N ha-1 in both the years. It was observed from the
above results that most of the available N was present in the 15-30 cm layer
indicating adequacy of N in the active root zone. Similar results were found
in the drip fertigation; however, insufficient redistribution time leads to
decreasing N content while increasing time. The highest soil water content in
microsprinkler was observed in the second layer (15-30 cm).
|
| Fig. 15(a-c): |
Nitrogen distribution pattern across
the lateral under microsprinkler at two months after sowing in 2008-2009
at (a) 24, (b) 48 and (c) 72 h |
|
| Fig. 16(a-c): |
Nitrogen distribution pattern across
the lateral under microsprinkler at two months after sowing in 2009-2010
at (a) 24, (b) 48 and (c) 72 h |
| Table 2: |
Nitrogen balance in drip in both the years |
 |
While comparing the N distribution in both the methods of irrigation, horizontal
distribution of N was more than the vertical distribution due to the non-uniform
distribution of water due to disc through of water in microsprinkler which is
contrary in the drip irrigation. As most of the water and nitrogen is available
in the active root zone (15-30 cm) in microsprinkler, this is most suitable
for the shallow rooted crops like garlic to facilitate crop uptake of water
and nitrogen as compared drip irrigation. The above results indicated that more
N is available horizontally in active root zone (15-30 cm).
Nitrogen balance in microirrigation fertigation during 2008-2009 and 2009-2010:
Nitrogen balance was computed using the available N, applied N, plant uptake
and soil residue N contents. The available N was estimated from the samples
taken before the sowing. Plant uptake and soil residue were measured from the
samples taken from after harvest. By deducting the N output from the N input
quantity the balance was assumed as leached beyond the root zone depth. Table
2 shows the N balance in the drip fertigation after harvest in both the
years in all the treatments. It revealed that the maximum plant uptake was in
120 kg ha-1 (90.47 kg ha-1) and the minimum N content
was in 40 kg N ha-1 (58.24 kg ha-1). The highest N by
the plant uptake, soil residue and leaching, was found to be in the treatment
of 120 kg N ha-1 in both the seasons.
| Table 3: |
Nitrogen balance in microsprinkler in both the years |
 |
It may be due to the reason that N applied was more than the recommended dose
leading to more plant uptake causing higher vegetative development. This could
be corroborated with the lower bulb yield in the N120 treatment as compared
to the N80 treatment.
Table 3 shows the N balance in microsprinkler in both the
years after harvest. Similar to the drip fertigation the leaching beyond the
root zone depth was estimated. It was observed that the plant uptake was higher
in N120 (67.53 and 64.47 kg N ha-1) in both the years. Similarly,
soil residues (96.47 and 104.34 kg N ha-1) and leaching (30.22 and
25.43 kg N ha-1) were highest in N120 treatment in both the years.
It can be inferred from the table that the leaching increased with increase
in the nitrogen applied.
In both the methods of fertigation despite the available N and applied N were
same, from plant up take and leaching points of view these were higher in drip
fertigation than microsprinkler. Also results in research study I indicated
that drip fertigation was giving the highest yield and quality. So, the drip
irrigation was better than the microsprinkler. However, microsprinkler facilitates
to increase the horizontal distribution, thereby decreasing the leaching than
drip fertigation.
CONCLUSION
It can be concluded that proper management of microirrigation with appropriate
amount of water and nitrogen significantly enhances the yield and quality of
garlic with maximum water and nitrogen use efficiency. In drip fertigation,
soil water content was relatively higher in upper soil layer (0-30 cm) and near
the emitter in all the 3 cases after irrigation (24, 48, 72 h after fertigation)
because of redistribution. Water content in all the soil layers decreased as
the distance from the emitter increased in the horizontal direction. The soil
water distribution decreased from the point of application to periphery of wetted
area. The favorable water content was maintained after 72 h after irrigation
in the active root zone. Comparing the water distribution in both the methods,
more horizontal movement was observed in microsprinkler than drip fertigation.
But, in drip irrigation vertical distribution was more than microsprinkler.
The present study revealed that water in both the methods of irrigation was
maintained in the range of 15-25%.
It can be concluded from the study that available nitrogen decreased from emitter
to the boundary of wetting zone in drip fertigation. Nitrogen availability decreased
with increasing horizontal distance in drip fertigation contrary to microsprinkler
fertigation.
In both the methods of irrigation, leaching of nitrogen increased with an enhancement
in rate of nitrogen application. However, nitrogen leaching was higher in drip
fertigation than the microsprinkler due to more vertical movement of soil water
leading to the movement of the nitrogen beyond the root zone. Nitrogen balance
for the study indicated that leaching of nitrogen beyond the root zone increased
with the level of nitrogen applied in both the methods of irrigation. Present
study demonstrated that fertigation through drip fertigation is more suitable
for growing of shallow rooted crop like garlic in terms of yield and its quality
and root uptake.
ACKNOWLEDGMENT
We acknowledge the Indian Agricultural Research Institute, New Delhi, India
for providing the financial support to first author during the study period.
Subscribe Today
