Introduction
The world’s population is continuously soaring up and an
increase in agricultural production remains a most challenging task to feed the
9.8 billion people by the end of 2050 (Alexandratos and Bruinsma 2012; Hassan et al. 2020a). Plants need sixteen
nutrients for optimum growth and productivity, nonetheless, nitrogen (N) is
mostly used nutrient by the plants. Thus, N is critical component of
agriculture and accounts for 50% world’s food production to meet food
challenges (Zhang et al. 2016).
Nitrogen is essential for normal plant growth and development, as it is a
structural component of different enzymes, proteins, and chlorophyll (Chattha et al. 2017a; Guo et al. 2019). Photosynthesis,
assimilates production, and leaf area are duration increases with the optimum N supply (Asibi et al. 2019) which in turn improves the
grain productivity (Rafiq et al.
2010). Nonetheless, losses from N fertilizers are 50% which is main source of lower
NUE (Coskun et al. 2017; Bindraban et al. 2020). Additionally, N losses
also increase the negative environmental footprints by increasing the
greenhouse gases emission and polluting the underground water (Coskun et al. 2017; Conijn et al. 2018).
Urea (46% N) is the most commonly used N fertilizer
across the globe owing to its cost-effectiveness. In Pakistan, 70% of applied
urea is lost into the environment and becomes unavailable for a plant which is
a challenging task, and these N losses adversely affect ecosystem, climate and
degrading the natural resources (Raza et
al. 2018). Therefore, to reduce these impacts on our environment, there is
a dire need to increase the fertilizer use efficiency and prolong the N
availability for optimum plant growth and development. The use of slow
releasing fertilizers is adopted to increase fertilizer use efficiency and
reduce N losses (Guo et al. 2019).
The slow releasing fertilizers have layers of different substance (oils,
nutrients) which decreases the rapid hydrolysis of applied fertilizer and
therefore prolong the nutrient availability and consequently increases crop
yield (Naz and Sulaiman 2016). Neem coated urea
possesses an excellent nitrification inhibition properties
to increase crop yield and NUE (Khandey et
al. 2017; Ghafoor et al. 2021).
The neem coated based nitrification inhibitors are degradable and
environmentally friendly and possess an appreciable potential to improve the
NUE (Dimkpa
et al. 2020). Several authors
reported promising potential of nitrification inhibition in different plant
parts and byproducts (oil) of neem to increase the crop yield and NUE under
conventional sowing methods (Patra et al.
2006; Khandey et al. 2017; Ali et al. 2020; Ghafoor et al. 2021). However, no information is
available linked with use of neem coated urea to improve NUE and crop yield
under BS and BCAF sowing.
Well-developed plant root system is necessary for the
better plant growth and nutrient uptake. The conventional sowing methods are
the major reason behind the lower crop productivity owing to reduction in
utilization efficiency of applied inputs (Khan et al. 2012; Chattha et al.
2020). Conventional sowing method (broadcasting) leads to poor stand establishment
and increases nutrient and water loss (Gathala et al. 2011). Therefore, in this context improved sowing methods
including ridge and bed sowing can play a significant role to improve crop
productivity, nutrient use, and water use efficiency. Ridges and beds provide
the loose layer of soil that ensures better root growth, root proliferation,
and increases water and nutrient uptake, ultimately increases final production
(Khan et al. 2012; Hassan et al. 2019; Iqbal et al. 2020). Wheat is an imperative crop cultivated across the
globe as imperious sources of nutrients, carbohydrates and calories (Chattha et al. 2017b; Hassan et al. 2019, 2021; Muhsin et al. 2021). Although many studies were
performed to improve the wheat crop yield and NUE through neem coated urea
under conventional BC and LS sowing method. Nonetheless, no information is
available related to effect of neem coated urea on NUE and performance of wheat
crop under BS and BCAF sowing methods. Thus, we hypothesized that neem coated
urea may improve wheat productivity and NUE through nitrification inhibition
and slow N release under different sowing methods. Therefore, this study was
conducted to determine best rate of neem coated urea for improving the wheat
productivity and NUE under different sowing methods in warm semi-arid
conditions.
Materials and
Methods
Experimental
site and soil
This study was
conducted in 2018–2019 and 2019–2020 at Agronomy Research Farm, University of
Agriculture Faisalabad, Pakistan. The studied site has a warm semi-arid climate
(Hassan at al. 2018, 2020b) and
weather conditions during the growing seasons are given in Fig. 1. The soil
samples from diverse parts of the experimental field were collected with the
help of augar and mixed to prepare composite samples and subjected to determine
different physico-chemical. The soil pH and organic matter was determined by
methods of Prasad et al. (2006) and
Walkley and Black (1934), whilst, nitrogen (N), phosphors (P) and potassium (K)
were determined by methods of AOAC (1990), Olsen et al. (1954) and Hanway and Heidel (1952) respectively. The soil was sandy loam
with pH 7.82, organic matter 8.8 g kg-1, %, available P 4.78 mg kg-1,
available K 170 mg kg-1 and total N 0.3 g kg-1.
Experimental details
The experiment was laid out in randomized complete
block design with a factorial arrangement having three replications. The
experiment comprised five
levels of urea application: control (no urea), 100% recommended normal urea
(100% RU), 100% recommended neem coated urea (100% RNCU), 75% recommended
normal urea (75% RU) and 75% recommended neem coated urea (75% RNCU). This was
cross combined with four sowing methods (SM): line sowing (LS), broadcast sowing (BC), broadcast augmented with furrow sowing (BCAF), and bed sowing (BS). With urea and neem coated urea, in
100% recommended urea fertilizer, N was applied at the rate of 150 kg ha-1,
while in 75% recommended urea application N was applied at the rate of 112.5 kg
ha-1. The seeds of neem were collected from different trees and
dried. After that they were crushed to extract the oil. 1000 mg neem oil was
used to coat one kg of urea. The net plot size of 4.5 × 10 m was kept during
both years of study. The experimental field was cultivated twice, followed by
planking to prepare the final seed bed for sowing. The crop was sown on 25th
and 27th November, during the %20450-460_files/image002.png)
Fig. 1: Mean temperature and rainfall (mm) during the 2018-2019
and 2019-2020
respective
2018–2019 and 2019–2020 growth seasons, by using a seed rate of 125 kg ha-1.
In broadcasting (BC), wheat seeds were broadcasted in the field, while in line
sowing (LS), the seeds were sown in 23 cm apart rows. In broadcast augment with
furrow (BCAF), the seeds were broadcasted in the field and 75 cm apart ridges
were made, whilst in bed sowing (BS) four lines of wheat were sown on each bed
having 30 cm furrow. The P and K fertilizers were applied to the crop at the
rate of 100 and 50 kg ha-1 of the two respective nutrients, in the
form of di-ammonium phosphate (18% N, 46% P2O5) and
sulphate of potash (50% K2O) and N was applied in the form of urea
(46% N) according to treatments. Complete quantity of P and K and half N was
applied at sowing, while the rest of N was applied at first irrigation. In
total, four irrigations were applied in each year. The first irrigation was
applied post 21 days after sowing (DAS), and the remaining three irrigations
were applied after 45, 85 and 110 DAS. The rest of the practices were kept
consistent with the general recommendations for the wheat crop in the surveyed
area.
Data collection
Destructive plant sampling was conducted to record the
growth attributes including leaf area index (LAI) and crop growth rate (CGR). One meter long row in each plot was harvested and separated
into leaves and stems. A sub-sample of leaves (5 g) was taken and leaf area was
measured by a leaf area meter (CI-202, CID Bio-Science) and LAI was determined
by given below formula as described by Watson (1947).
%20450-460_files/image004.png){kind=small}
1
Additionally, a sub-sample of plants (5 g) was taken
from the harvested plants and oven-dried (75°C) until constant weight to determine
the dry weight and CGR was determined by the method of Hunt (1978) with
equation 2.
%20450-460_files/image006.png){kind=small}
2
Here W2 and W1 show the dry matter at first and second harvesting,
whereas T2 and T1 showing the time of second and first harvesting. The first
LAI and CGR were determined at 30 DAS, and subsequent measurements were taken
at 15-day intervals. Similarly, ten plants were selected and plant height was
measured, spikelet and grains per spike were counted and averaged. At harvest
maturity, the complete plots were harvested and sun-dried and weighed to
determine the biological yield and later on threshed to determine grain yield
and converted into t ha-1. A sub-sample of 1000 grains were taken
from the threshed grains and weighed to determine the thousand-grain weight
(TGW). Additionally, the harvest index was assessed as the ratio of grain to
biological yield.
Nutrients uptake and N efficiency assessments
The plant materials including the grains and straw (10
g) were oven dried (75°C) till constant weight. The N contents in straw were
determined by the methods of Jackson (1962), whereas for N in grain, the
percentage of protein contents (obtained by kernelyzer) was divided by 5.7 to
get the percentage of N contents in grains (Herridge 2013). The dried grain and straw samples were wet digested (HClO4:
HNO3 3:10 ratio) filtered and
diluted with distilled water, and the P contents were determined by the inductively
coupled plasma mass spectrometry, whereas the K contents were determined by
flame photometer. The obtained values of nutrients were multiplied with the
total dry matter to determine the NPK uptake (Fageria et al. 1997). For determination of NPK a set of three replicate was
used for each treatment and later on average was taken. The agronomic use
efficiency (AUE) was determined by this formula (Jadon et al. 2018):
%20450-460_files/image008.png){kind=small}
(3)
The N uptake efficiency (NUptE) was determined by the
following formula (Xu et al. 2020):
%20450-460_files/image010.png){kind=small}
(4)
The N use efficiency (NUE) was calculated by the following
equation (Xu et al. 2020):
%20450-460_files/image012.png){kind=small}
(5)
Lastly, N productive efficiency (NPE) was calculated by
following formula (Xu et al. 2020):
%20450-460_files/image014.png){kind=small}
(6)
Economic
analysis and resource use efficiency
The economic analysis was performed to estimate the
feasibility of diverse sowing methods and neem coated urea based on variable
costs related to the different sowing methods and fertilizer applications
(CIMMYT 1998). The cost of fertilizers, irrigation, herbicides, along with
their application charges and cost of seeds were considered as a fixed cost.
Moreover, the costs for different sowing methods, and normal and neem coated
urea were treated as variable costs. The net benefit was calculated by
subtracting the total cost from the gross income, while the net benefit-cost
ratio was determined by dividing the gross income by total cost (CIMMYT 1998).
Additionally, the resource use efficiency (RUE) was determined by the methods
of Farooq and Nawaz (2014).
%20450-460_files/image016.png){kind=small}
7
Statistical
analysis
Data regarding growth, production, N accumulation and
various N-efficiency parameters were analyzed by Fisher’s analysis of variance
(ANOVA) technique using STATISTIX 8.1 (Analytical Software, Inc., Tallahassee,
FL, USA). The differences among treatments were separated using the least
significant difference (LSD) test at 5% probability level (Steel et al. 1997). The data of each year was
separately analyzed and therefore both years’ data presented separately. The
data set was also subjected to Pearson’s correction to determine the reciprocal
inter-relations among studied traits.
Results
Growth
attributes
Plant growth
parameters LAI, CGR and plant height were significantly influenced by the neem
coated urea and sowing methods (Table 1). Initially, there was a non-significant
difference among treatments in both years for LAI; however, the difference
became wider when LAI reached maximum values at 75 days after sowing (DAS),
before LAI started declining with senescence (Fig. 2). Highest paired LAI values
at 75 DAS were recorded with the application of both (100 and 75% RNCU), while lowest paired LAI values were
shown for urea at the two N doses (100 and 75% RU) (Fig. 2). Among SM; maximum
LAI was noticed in bed sowing (BS) closely followed by line sowing (LS), while
the lowest LAI in both growing seasons was noticed in BCAF. Crop growth rate
also showed the same and reached a peak at 75–90 DAS, and afterward, it started
decreasing (Fig. 3). Maximum CGR in both seasons was noted with 100% RNCU that
remained similar with75% RNCU, while lowest CGR was recorded with the
application of 100% RU (Fig. 3). Similarly, maximum plant height was recorded
in 100% RNCU, followed by 75% RNCU that was at par statistically with 100% RU and
minimum plant height was recorded
with 75% RU in both years (Table 4).
Yield and yield components
The yield
contributing traits showed a significant response to neem coated urea and SM
(Table 1 and 2). In both study years, the maximum number of productive tillers
and spikelet/spike was obtained with 100% RNCU followed by 75% RNCU, whereas
the lowest number of tillers and spikelet/spike was obtained with 75% RU (Table
4). Among SM, maximum number of tillers and spikelet/spike was recorded in BS,
while lowest number of tillers and spikelet/spike was recorded in BCAF (Table
4). The maximum number of grains/spike was also
recorded in 100% RNCU, quite closely followed by 75% RNCU, while the lowest
number of grains/spike was obtained at par in 100 and 75% RU (Table 4). Bed
sowing performed best in terms of grains/spike, followed by LS; conversely, the
two broadcast sowing methods (BC and BCAF) performed worst in terms of
grains/spike during both seasons (Table 4).
The application of 100% RNCU passed all treatments and
resulted in highest thousand-grain weight (TGW), whereas lowest TGW was
reported in 75% RU (Table 5). There were also significant differences in TGW
among SM; BS remained at top with maximum TGW, followed by LS, while BCAF
remained at lowest ranking with minimum TGW (Table 5). Likewise, in both seasons
maximum grain yield was recorded with 100% RNCU followed by 75% RNCU, while
lowest grain yield was recorded in 75% RU (Table 5). The same ranking was shown
in biological yield, whereas in harvest index higher values were observed, in
general, for the full dose of N (100% RNCU and 100 RU) (Table 5). Amid SM,
maximum grain yield was recorded in BS and the overall trend was BS > LS >
BC > BCAF (Table 5). BS also resulted in maximum biological yield and HI,
and the same overall trend (BS > LS > BC > BCAF) was observed (Table
5).
Nutrients uptake and nitrogen use efficiency
The
nutrient (NPK) uptake was significantly affected by
Table 1: Analysis of variance for the effect different sowing
methods and rates of neem coated urea yield traits of wheat crop
|
Treatments |
Plant height (cm) |
Productive tillers/m2 |
Spikelet/spike |
Grains/spike |
||||
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
|
Sowing methods (SM) |
571.75** |
822.95* |
3236.40* |
2898.98** |
8.89* |
5.37** |
91.39** |
97.91** |
|
Urea application (UA) |
510.22* |
232.76* |
2371.19* |
3237.73** |
6.71* |
5.47** |
60.44* |
96.76** |
|
SM × UA |
7.99NS |
10.36NS |
356.69NS |
411.42* |
0.87NS |
1.37 NS |
5.79NS |
10.52* |
**:
highly significant, *: significant, NS: non-significant
Table 2: Analysis of variance for the effect different sowing
methods and rates of neem coated urea on yield and yield traits of wheat crop
|
Treatments |
1000 grain weight |
Grain yield (g/plant) |
Biological yield (g/plant) |
Harvest index (%) |
||||
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
|
Sowing methods (SM) |
60.03** |
64.18** |
5.563* |
2.57** |
5.19* |
7.00** |
148.20** |
35.26** |
|
Urea application (UA) |
100.978 |
134.06** |
7.28* |
12.30** |
16.84** |
26.24* |
128.31** |
247.69** |
|
SM × UA |
3.81NS |
3.52* |
0.32NS |
0.15 NS |
0.11NS |
2.33* |
25.21NS |
19.76 NS |
**:
highly significant, *: significant, NS: non-significant
Table 3: Analysis of variance for the effect different sowing
methods and rates of neem coated urea on nutrients uptake and nitrogen use
efficiency parameters wheat crop
|
Treatments |
N uptake |
P uptake |
K uptake |
AUE |
NUptE |
NUE |
NPE |
|||||||
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
|
Sowing methods (SM) |
603.40* |
816.91* |
1.57* |
3.59** |
363.08* |
308.29** |
6.65** |
2.98** |
0.013** |
0.010** |
10.07** |
9.16** |
22.29** |
16.86** |
|
Urea application (UA) |
3700.44* |
4401.4* |
4.67* |
6.58** |
539.04* |
1151.85* |
0.75** |
0.42* |
0.004** |
0.015** |
3.83** |
6.68* |
24.64** |
20.39** |
|
SM × UA |
5.83NS |
20.25 NS |
0.034 NS |
0.16 NS |
8.24 NS |
10.32NS |
0.01NS |
0.04NS |
0.002 NS |
0.001 NS |
0.24 NS |
0.27 NS |
0.33NS |
0.24 NS |
**: highly significant, *:
significant, NS: non-significant, N: nitrogen, P: phosphorus, K: potassium, AUE:
agronomic use efficiency, NUptE: nitrogen, uptake
efficiency, NUE: nitrogen use efficiency, NPE: nitrogen productive efficiency
Table 4: Effect of different sowing methods and rates of neem
coated urea on the yield traits of wheat crop
|
Urea application |
Plant height (cm) |
Productive tillers/m2 |
Spikelet/spike |
Grains/spike |
||||
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
|
No urea |
84.83 D |
94.67D |
265.00D |
266.67E |
12.43B |
13.08E |
37.42D |
38.16D |
|
100% RU |
96.83BC |
100.17BC |
282.58BC |
290.00C |
13.46B |
14.04C |
40.33BC |
42.67C |
|
100% RNCU |
102.58A |
106.83A |
301.67A |
309.33A |
14.33A |
14.88A |
43.25A |
45.67A |
|
75% RU |
95.33B |
99.17C |
276.58C |
283.67C |
12.71C |
13.67D |
39.92C |
42.17C |
|
75% RNCU |
97.58B |
101.75B |
291.83AB |
301.00B |
13.49B |
14.32B |
41.16AB |
44.33B |
|
LSD (P
≤ 0.05) |
2.14 |
2.17 |
5.23 |
6.06 |
0.17 |
0.17 |
1.09 |
0.39 |
|
Sowing methods |
|
|
|
|
|
|
|
|
|
LS |
96.87B |
102.00B |
285.73B |
292.93B |
13.25B |
14.10B |
41.67B |
43.33B |
|
BC |
91.20C |
95.07C |
282.73B |
285.93C |
13.20B |
13.79C |
39.36C |
41.80C |
|
BCAF |
89.67C |
94.60C |
264.93C |
274.20D |
13.22C |
13.34D |
38.00C |
39.60D |
|
BS |
103.00A |
110.40A |
300.73A |
307.47A |
14.27A |
14.77A |
43.54A |
45.67A |
|
LSD (p
≤ 0.05) |
3.83 |
2.17 |
7.72 |
1.51 |
0.19 |
0.05 |
0.70 |
0.60 |
Means with different letters differed at 0.05 P level. 100% RU: 100% recommended normal urea, 100% RNCU: 100%
recommended neem coated urea, 75% RU: 75% recommended normal urea 75% RNCU: 75%
recommended neem coated urea. LS: Line sowing, BC: broadcast sowing, BCAF:
broadcast augmented with furrow, BS: Bed sowing.
Table 5: Effect of different sowing methods and rates of neem
coated urea on yield traits and yield of wheat crop
|
Urea application |
1000 grain weight (g) |
Grain yield (t ha-1) |
Biological yield (t ha-1) |
Harvest index (%) |
|||||
|
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
|
No urea |
35.31D |
36.32D |
3.14D |
3.17D |
10.26D |
10.74D |
30.74B |
29.63C |
|
|
100% RU |
38.48C |
41.29C |
4.70C |
5.43B |
12.27B |
13.26BC |
37.69A |
39.55AB |
|
|
100% RNCU |
42.95A |
45.27A |
5.09A |
5.56A |
13.24A |
14.55A |
37.00A |
38.46B |
|
|
75% RU |
37.57C |
40.50C |
4.50D |
5.11C |
11.90C |
12.91C |
38.25A |
40.98A |
|
|
75% RNCU |
40.47B |
43.19B |
4.94B |
5.48AB |
13.03A |
14.11AB |
38.36A |
39.36AB |
|
|
LSD (P
≤ 0.05) |
0.55 |
0.43 |
0.055 |
0.047 |
0.137 |
0.537 |
0.655 |
1.03 |
|
|
Sowing methods SM) |
|
|
|
|
|
|
|
|
|
|
LS |
39.61B |
42.23AB |
4.66B |
5.01B |
12.28B |
13.56A |
37.67B |
36.87BC |
|
|
BC |
38.20C |
40.97B |
4.39C |
4.94B |
11.91C |
12.95AB |
36.73B |
37.86B |
|
|
BCAF |
36.58D |
38.16C |
3.69D |
4.42C |
11.49D |
12.22B |
32.22C |
36.04C |
|
|
BS |
41.31A |
43.45A |
5.15A |
5.42A |
12.88A |
13.72A |
39.65A |
39.61A |
|
|
LSD (P
≤ 0.05) |
1.27 |
1.76 |
0.059 |
0.063 |
0.132 |
0.515 |
1.33 |
0.647 |
|
Means with different letters differed at 0.05 P level. 100% RU: 100%
recommended normal urea, 100% RNCU: 100% recommended neem coated urea, 75% RU:
75% recommended normal urea 75% RNCU: 75% recommended neem coated urea. LS:
Line sowing, BC: broadcast sowing, BCAF: broadcast augmented with furrow, BS:
Bed sowing.
%20450-460_files/image018.jpg)
Fig. 2: Effect of neem coated urea (A and B) and sowing
methods (C and D) on the leaf area index of wheat crop during 2018-19 and 2019-20.
100% RU: 100% recommended normal urea,
100% RNCU: 100% recommended neem coated urea, 75% RU: 75% recommended normal
urea 75% RNCU: 75% recommended neem coated urea. LS: Line sowing, BC: broadcast
sowing, BCAF: broadcast augmented with furrow, BS: Bed sowing.
%20450-460_files/image020.jpg)
Fig. 3: Effect of neem coated urea (A and B) and sowing
methods (C and D) on crop growth rate of wheat crop during 2018-19 and 2019-20. 100% RU: 100% recommended normal urea, 100% RNCU: 100%
recommended neem coated urea, 75% RU: 75% recommended normal urea 75% RNCU: 75%
recommended neem coated urea. LS: Line sowing, BC: broadcast sowing, BCAF:
broadcast augmented with furrow, BS: Bed sowing.
%20450-460_files/image022.jpg)
Fig. 4: Pearson’s correlations between the studied traits. PH:
plant height, PT; productive tillers, SPS: spikelet’s
per spike, GPS: grains per spike, TGW: thousand grain weight; GY: grain yield,
BY: biological yield, HI: harvest index, NUT: nitrogen uptake, PUT: phosphorus
uptake, PUT: potassium uptake, AUE: agronomic use efficiency, NUTE: nitrogen
uptake efficiency, NUE: nitrogen use efficiency, NPE: nitrogen productive
efficiency.
both nitrogen application and SM (Table 3). In both years
the highest N, P and K uptake was shown with 100% RNCU while the lowest N, P
and K uptake was observed with 75% RU (Table 6). There were significant
differences among SM for nutrient uptake; BS determined the highest uptake of
the three elements; LS ranked second, followed by BC and lastly BCAF (Table 6).
The two factors nitrogen application and SM had a significant impact on
nitrogen efficiency traits in both years (Table 3). In both years the highest
agronomic use efficiency (AUE), nitrogen use efficiency (NUE), N uptake
efficiency and N productive efficiency were evidenced by100% RNCU, followed by
75% RNCU; conversely, the lowest levels of the four traits were shown by 75%
RU-U (Table 7). Sowing methods also exhibited significant differences for AUE,
NUE, N uptake and productive efficiency; again, BS achieved the highest levels,
followed by LS, BC and lastly BCAF (Table 7).
Economic
analysis and resource use efficiency
Maximum net benefit and benefit-cost ratio (BCR) was
achieved with the application of 75% RNCU followed by 100% RNCU, while lowest
net benefit and BCR was obtained with application of 75% RU (Table 8). Among
SM, maximum net benefit and BCR were recorded in BS, whereas minimum net
benefit and BCR were noted in BCAF (Table 5). Similarly, resource use
efficiency (RUE) remained highest in 75% RNCU, followed by 100% RNCU-NCU, while
the lowest RUE was recorded in 75% RU (Table 8). Moreover, in the case of SM,
BS resulted in maximum RUE, followed by LS and BC, while minimum RUE was
recorded in BCAF (Table 8).
Pearson’s
correlation
Pearson’s correlations showed a significant positive
association among most of the studied traits (Fig. 4). The values indicate a
positive correlation among productive tillers, thousand grain weight,
spikelets/spike, and grain yield. Similarly, a positive association was also
observed between nitrogen efficiency traits and grain yield, which is
consistent with meaning of these traits (Fig. 4).
Discussion
The current findings support the hypothesis that neem
coated urea would improve wheat N efficiency, productivity and net economic returns
under varying sowing methods. Neem coated urea considerably enhanced wheat
growth, as shown by the functional growth traits leaf area index (LAI) and crop
growth rate (CGR) (Fig. 1 and 2) and the morphological traits plant height
(Table 4). Neem coating ensures slower release of N and increases N
availability for a longer period (Sannagoudra et al. 2012; Ghafoor et al.
2021), which in turn improves assimilates production and resultantly leads to a
marked improvement in growth traits. LAI has a direct association with the
number of leaves; therefore, the observed increase in LAI by neem coated urea
was due to an increase in leaves/plants. Similarly, larger leaves ensure better
light-harvesting, which in turn improves dry matter production and resultantly
increases CGR (Fig. 3) and final production (Hassan et al. 2019). Diverse sowing methods also had a significant impact
on LAI, CGR and plant height; however, bed sowing (BS) performed significantly
better compared to other methods. The sowing on beds and ridges ensures the
provision of loose fertile soil which provides a
better environment for root growth and favors a better nutrient and
water uptake and therefore, facilitates better assimilation and dry matter
production (Fig. 3) and resultantly leads to the production of taller plants
with higher LAI and CGR (Hassan et al.
2019; Chattha et al. 2020).
Neem
coated urea significantly increased grain yield and its components in both
seasons (Table 4 and 5). Neem coating induces slower release of N and reduces
potential N losses, which in turn ensures a better N availability to the
benefit of yield and yield contributing traits (Zhang et al. 2019). Additionally, neem coating also reduces NO3-
availability for denitrifying bacteria, which in turn increases nitrogen
efficiency and consequently leads to an increase in both grain and biomass
yield (Kundu et al. 2013;
Alonso-Ayuso et al. 2016).
Significant increase in yield components, grain and biological yield was
observed in bed sowing compared to other methods (Table 4 and 5). Favorable
soil conditions created in BS ensured efficient nutrient and water uptake,
which might be the reason for Table 6: Effect of different
sowing methods and rates of neem coated urea on nutrients uptake
|
Urea application |
Nitrogen uptake (kg ha-1) |
Phosphorus uptake (kg ha-1) |
Potassium uptake (kg ha-1) |
|||
|
|
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
2018-2019 |
2019-2020 |
|
No urea |
76.92D |
78.58D |
11.44B |
11.52C |
120.42D |
122.50D |
|
100% RU |
114.67B |
118.83B |
12.83A |
13.06AB |
132.50B |
137.58B |
|
100% RNCU |
119.67A |
124.17A |
13.00A |
13.39A |
137.25A |
147.08A |
|
75% RU |
110.17C |
116.42C |
12.56A |
12.80B |
128.50C |
133.58C |
|
75% RNCU |
117.08AB |
123.00A |
12.86A |
13.18A |
135.50A |
144.75A |
|
LSD (P
≤ 0.05) |
1.31 |
1.04 |
0.247 |
0.18 |
1.14 |
1.27 |
|
Sowing methods |
|
|
|
|
|
|
|
LS |
109.20B |
116.13B |
12.63AB |
12.94B |
132.67B |
139.47B |
|
BC |
106.20B |
108.40C |
12.44B |
12.60C |
129.47C |
134.33C |
|
BCAF |
100.20C |
104.40D |
12.10C |
12.23D |
124.80D |
131.93D |
|
BS |
115.40A |
120.73A |
12.87A |
13.38A |
136.40A |
142.07A |
|
LSD (P
≤ 0.05) |
1.82 |
0.811 |
0.130 |
0.91 |
0.83 |
0.96 |
Means with different letters differed
at 0.05 P level. 100% RU: 100%
recommended normal urea, 100% RNCU: 100% recommended neem coated urea, 75% RU:
75% recommended normal urea 75% RNCU: 75% recommended neem coated urea. LS:
Line sowing, BC: broadcast sowing, BCAF: broadcast augmented with furrow, BS: Bed
sowing
Table 7: Effect of different sowing methods and rates of neem
coated urea on agronomic, N uptake, N use and N productive efficiencies
|
Urea application |
Agronomic use efficiency (kg/kg) |
N uptake efficiency (kg/kg) |
N use efficiency (kg/kg) |
N productive efficiency (kg/kg) |
||||
|
|
2018–2019 |
2019–2020 |
2018–2019 |
2019–2020 |
2018–2019 |
2019–2020 |
2018–2019 |
2019–2020 |
|
No urea |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
100% RU |
13.86B |
15.45C |
0.79B |
0.82C |
29.68AB |
30.67BC |
35.76B |
38.27B |
|
100% RNCU |
17.33A |
21.30A |
1.04 |
1.09A |
30.31A |
31.75A |
37.50A |
39.47A |
|
75% RU |
9.05D |
12.97D |
0.76D |
0.79C |
28.95B |
30.09C |
34.33C |
36.50C |
|
75% RNCU |
11.99C |
20.15B |
0.97B |
1.03B |
29.86AB |
31.42AB |
37.09A |
38.99AB |
|
LSD (P
≤ 0.05) |
0.33 |
0.37 |
0.021 |
0.006 |
0.92 |
0.84 |
0.93 |
1.03 |
|
Sowing methods |
|
|
||||||
|
LS |
12.41B |
14.80B |
0.72B |
0.77B |
30.08AB |
31.17B |
31.72B |
38.75B |
|
BC |
8.83C |
14.31B |
0.70B |
0.72C |
29.58B |
30.61BC |
35.44C |
37.67C |
|
BCAF |
5.08D |
10.67C |
0.66C |
0.69D |
28.50C |
30.05C |
34.72C |
37.06C |
|
BS |
15.46A |
16.94AA |
0.77A |
0.80A |
30.66A |
32.10A |
37.80A |
39.75A |
|
LSD (P
≤ 0.05) |
0.34 |
0.52 |
0.011 |
0.02 |
0.85 |
0.87 |
0.91 |
0.74 |
Means with different letters differed at 0.05 P level. 100% RU: 100% recommended normal urea, 100% RNCU: 100%
recommended neem coated urea, 75% RU: 75% recommended normal urea 75% RNCU: 75%
recommended neem coated urea. LS: Line sowing, BC: broadcast sowing, BCAF:
broadcast augmented with furrow, BS: Bed sowing.
Table 8: Economic analysis and resource use efficiency for the
effect of different sowing methods and different rates of neem coated urea
|
Sowing methods |
Urea application |
GY |
AGY |
SY |
ASY |
GV |
SV |
GI |
PC |
VC |
TC |
NB |
BCR |
RUE |
|
LS |
No urea |
3.12 |
2.81 |
10.50 |
9.45 |
552.86 |
261.67 |
814.53 |
474.26 |
65.66 |
539.92 |
274.60 |
1.51 |
0.51 |
|
|
100% RU |
4.97 |
4.47 |
12.56 |
11.31 |
878.85 |
313.05 |
1191.90 |
479.22 |
65.66 |
544.88 |
647.02 |
2.19 |
1.19 |
|
|
100% RNCU |
5.38 |
4.84 |
15.23 |
13.71 |
951.43 |
379.55 |
1330.97 |
458.98 |
65.66 |
524.65 |
806.33 |
2.54 |
1.54 |
|
|
75% RU |
5.24 |
4.72 |
13.10 |
11.79 |
928.12 |
326.34 |
1254.46 |
462.70 |
65.66 |
528.36 |
726.10 |
2.37 |
1.37 |
|
|
75% RNCU |
5.50 |
4.95 |
13.63 |
12.27 |
972.96 |
339.71 |
1312.68 |
443.84 |
65.66 |
509.50 |
803.18 |
2.58 |
1.58 |
|
BC |
No urea |
3.19 |
2.87 |
10.93 |
9.84 |
564.96 |
272.39 |
837.34 |
474.26 |
62.50 |
536.76 |
300.58 |
1.56 |
0.56 |
|
|
100% RU |
4.65 |
4.19 |
12.38 |
11.14 |
823.68 |
308.40 |
1132.08 |
479.22 |
62.50 |
541.72 |
590.36 |
2.09 |
1.09 |
|
|
100% RNCU |
5.18 |
4.66 |
13.16 |
11.85 |
916.91 |
328.00 |
1244.91 |
458.98 |
62.50 |
521.48 |
723.43 |
2.39 |
1.39 |
|
|
75% RU |
5.05 |
4.55 |
12.39 |
11.15 |
894.49 |
308.85 |
1203.34 |
462.70 |
62.50 |
525.20 |
678.14 |
2.29 |
1.29 |
|
|
75% RNCU |
5.26 |
4.73 |
13.30 |
11.97 |
930.48 |
331.36 |
1261.84 |
443.83 |
62.50 |
506.33 |
755.52 |
2.49 |
1.49 |
|
BCAF |
No urea |
3.08 |
2.78 |
9.39 |
8.45 |
545.78 |
233.88 |
779.66 |
474.26 |
75.16 |
549.42 |
230.24 |
1.42 |
0.42 |
|
|
100% RU |
4.09 |
3.68 |
11.66 |
10.49 |
723.08 |
290.54 |
1013.62 |
479.22 |
75.16 |
554.37 |
459.25 |
1.83 |
0.83 |
|
|
100% RNCU |
4.40 |
3.96 |
12.74 |
11.46 |
779.14 |
317.45 |
1096.59 |
458.98 |
75.16 |
534.14 |
562.45 |
2.05 |
1.05 |
|
|
75% RU |
4.29 |
3.86 |
12.39 |
11.15 |
759.96 |
308.77 |
1068.73 |
462.70 |
75.16 |
537.85 |
530.88 |
1.99 |
0.99 |
|
|
75% RNCU |
4.42 |
3.98 |
13.13 |
11.82 |
782.97 |
327.21 |
1110.18 |
443.84 |
75.04 |
518.88 |
591.30 |
2.14 |
1.14 |
|
BS |
No urea |
3.22 |
2.90 |
11.20 |
10.08 |
569.97 |
279.03 |
849.00 |
474.26 |
70.41 |
544.67 |
304.33 |
1.56 |
0.56 |
|
|
100% RU |
5.52 |
4.97 |
13.03 |
11.73 |
977.39 |
324.80 |
1302.19 |
479.22 |
70.41 |
549.63 |
752.56 |
2.37 |
1.37 |
|
|
100% RNCU |
5.90 |
5.31 |
14.05 |
12.64 |
1044.36 |
350.01 |
1394.37 |
458.98 |
70.41 |
529.39 |
864.98 |
2.63 |
1.63 |
|
|
75% RU |
5.68 |
5.12 |
13.21 |
11.89 |
1006.00 |
329.12 |
1335.13 |
462.70 |
70.41 |
533.11 |
802.02 |
2.50 |
1.50 |
|
|
75% RNCU |
6.14 |
5.52 |
14.65 |
13.18 |
1085.95 |
365.01 |
1450.96 |
443.84 |
70.41 |
514.25 |
936.71 |
2.82 |
1.82 |
100% RU: 100% recommended normal urea, 100% RNCU: 100%
recommended neem coated urea, 75% RU: 75% recommended normal urea 75% RNCU: 75%
recommended neem coated urea. LS: Line sowing, BC: broadcast sowing, BCAF:
broadcast augmented with furrow, BS: Bed sowing. GY: grain yield, AGY: adjusted
grain yield, SY: straw yield, ASY: adjusted straw yield, GV: grain value, SV:
straw value, GI: gross income, PC: permanent cost, VC: variable cost, TC: total
cost, NB: net benefit, BCR: benefit cost ration, RUE: resource use efficiency.
improved yield and
its components. The vigorous stand establishment, higher LAI, CGR, tillers,
grains/spike and grain yield are the reflection of higher nutrient and water
uptake in BS (Mahmood et al. 2013;
Iqbal et al. 2020). Likewise, maximum
biological yield in BS was due to positive conditions created by the bed sowing
resulting in better root growth that enabled the plants to take up more
nutrients and water to produce higher LAI and CGR and consequently higher
biomass production (Table 5).
The
results indicate that N, P, and K uptake was significantly increased with neem
coated urea (Table 6). The increase in uptake of N by neem coated can be due to
the fact that neem coating increased the synchronization between plant N demand
and fertilizer release throughout the growing period (Wang et al. 2015) by reducing the nitrification speed that is not
limiting in the warm climate of Punjab, Pakistan. Moreover, neem coated urea
also promoted P and K uptake (Table 6). Nitrogen application increases root
branching closer to the soil surface where the nutrient level is higher (Postma
et al. 2014); therefore, the observed
increase in P and K uptake by neem coated urea was due to an increase in root
growth. Neem coated urea also significantly improved, AUE, N uptake efficiency
(NUptE), NUE and N productive efficiency (NPE)
compared to the normal urea (Table 4). The recovery efficiency in neem coated
urea increased due to inhibition of nitrification and retaining of NH4+-N
that can be used by plants for a longer period, in turn improving the overall
utilization efficiency of applied fertilizers. Moreover, in neem coated urea,
rate of N availability becomes slow and N uptake is increases, which in turn
reduces the N losses and increases AUE, NUE, and N uptake efficiency (Ning et al. 2012; Jadon et al. 2018). Bed sowing resulted in maximum improvement in
nutrient uptake and N utilization compared to other sowing methods (Table 6 and
7). Bed and ridge sowing provide a better growing environment to roots compared
to other methods of sowing, thanks to reduced risk of flooded wheat plants in
case of unusually wet periods. This suggested that sowing on beds enabled the
plants to utilize the applied nutrients more efficiency compared to flat sowing
(Rehman et al. 2011), which therefore
improves AUE, NUptE and NUE.
Conclusion
The application of neem coated urea
(150 kg N ha-1) significantly improved wheat growth, yield, nutrient
uptake, and nitrogen use efficiency through extended N availability. However,
it was practically at par with 75% recommended neem coated urea (122 kg ha-1),
which performed generally better than the 100 and 75% normal urea. Moreover,
among sowing methods, bed produced the maximum yield and resulted in maximum
nutrient uptake, nitrogen use efficiency and economic returns than other sowing
methods. Therefore, higher yield, nutrient uptake, nitrogen use efficiency and
economic returns, jointly imparted by neem coated urea and bed sowing appears a
promising approach to improve wheat productivity in warm, semi-arid regions at low
latitudes.
Acknowledgements
We are thankful to Dr. Lorenzo Barbanti, Department
of Agricultural and Food Sciences, University of Bologna Italy for his critical
reading and suggestions to improve the quality of manuscript.
Author
Contributions
MUC and IK planned the experiment,
AR conducted the experiment and interpreted the results, MTA helped in data
collection, AR, MUC, MBC, MN, MUH made the original draft, MAA, MMI, FH, FA,
FAK and MK reviewed and edited final draft.
Conflict
of Interest
The authors declare no conflict of interest.
Data
Availability
Not applicable.
Ethics
Approval
Not applicable.
Funding Source
This work was not supported by
any specific funding.
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