Introduction
Rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system
(RWS) is one the major cropping systems practiced on an area of 13.5 million
hectares (Mha) in South Asia (FAO 2016). In conventional RWS, rice is grown by
transplanting the nursery seedling into a puddled field; however, the following
wheat crop is sown in plowed and pulverized soil. However, puddling in rice
deteriorates soil physical quality (Bertolino et al. 2010; Farooq and
Nawaz 2014; Akmal et al. 2015), which adversely impacts root and shoot
growth of the following winter crops (McDonald et al. 2006) by reducing
nutrient and water availability (Ishaq et al. 2001). Indeed, puddling
results in the formation of a strong crust that inhibits wheat seedling
emergence (Micucci and Taboada 2006; Mohanty et al. 2006). This crust
does not allow roots to go deep because of low porosity and too high mechanical
impedance as these plow pan layers are situated shallow than the normal rooting
depth (Bruand et al. 2004). Moreover, late maturity, and harvest of
basmati rice further delay wheat planting in this system (Farooq et al.
2008), which drastically reduces yield and profitability (Hussain et al. 2012).
Due to ever-rising population and climate change, the
importance of sustainable management approaches has increased to retain and
amend soil quality, and to increase the crop production (Komatsuzaki and Ohta
2007; Lal 2009). To meet the challenges of the future, the idea of conservation
agriculture (CA) has been recognized as an integrated management strategy
(Verhulst et al. 2010). Conservation
agriculture, which involves least soil disturbance, retains residue cover and
diversified crop rotation, offers a pragmatic option to resolve the edaphic and
time conflicts in the conventional RWS (Farooq and Nawaz 2014; Lal 2015). Water-saving
rice production systems, including direct seeded aerobic rice (DSAR) culture,
may resolve the edaphic constraints while also reducing water and energy input
(Oliver et al. 2008; Farooq et al. 2009, 2011). Direct seeded
aerobic rice also matures earlier than puddled flooded transplanted rice
(PudTR), thus allowing the timely sowing of the following crop (Farooq et
al. 2008). Direct seeding in the aerobic environment also improves soil
physical quality for post rice winter cereals (Farooq and Nawaz 2014) by
enhancing deeper root penetration and improving water and nutrients uptake.
Moreover, no-tillage (NT) facilitates early wheat sowing and reduces the
production cost (Farooq and Nawaz 2014). In contrast, plow tillage (PT) often
degrades the soil structure (Qureshi et al. 2003; D’Haene et al. 2008), and depletes soil organic
matter (SOM) content (Lal 2015).
For wheat sowing, zero tillage helps mitigate labor cost
and use of fuel (Lal 2007; Shahzad et al.
2017). Minimum disturbing of soil protects soil and water reserves, limits
utilization of farm energy, and raises the crop production. This technique
improves soil biological and physical properties (Alvarez and Steinbach 2009).
Direct tilling is used as a modality of conservation tillage and accepted as
the best way of protecting the soil surface from structure deterioration and
erosion (Reeves et al. 2005). It is
found that conservation tillage increases the stability of aggregate, organic
matter, K+ ion and biotic activities (Munkholm et al. 2008; Schjonning et al.
2011; Munkholm and Hansen 2012). Reduced tillage causes stratification in the
soil layer that affects chemical traits and organic matter in the soil
(Franzluebbers 2002; Jones et al.
2007). No-tillage influences many soil traits such as porosity, pore
connectivity, bulk density, infiltration rate, and water retention capability,
including chemical attributes such as OM content and status of nutrients in the
soil (Kribaa et al. 2001). In the
seedbed, seed germination and plant emergence are influenced by soil
temperature and soil moisture. During the growing period of crop, the high soil
moisture is maintained by conservation tillage (Tan et al. 2002; Alletto et al.
2011).
The use of cover crops in rotation with the main crop
provides a range of dynamic services and advantages. Winter cover exploits soil
for nutrient and minimizes the losses of nutrients (Fageria et al. 2005; Gomez et al. 2009;
Munkholm and Hansen 2012). It is observed that cover crops amend soil health
and carbon sequestration in soil (Motta et
al. 2007; Weil and Kremen 2007; Mutegi et
al. 2013). Cover crops eliminate the need for intensive tilling by reducing
the problem of soil compaction. Thomsen and Christensen (2004) examined that
the winter legume cover alleviates the soil compaction problem in compacted
sandy loam field and may be used as a replacement to intensive tillage practice
due to the formation of bio-pores. Brassica cover crops have been reported for
its positive effect on soil structure and health (Williams and Weil 2004; Chen
and Weil 2010). Elements of conservation tillage such as no-till and shallow
till produce problems for topsoil structure and cover crops alleviate this
problem by increasing biological activity in the soil and producing bio-pores
(Soane et al. 2012). Existence of
crop residues on the soil surface declines the evaporation rate (Jalota et al. 2006), disintegration of soil
particles (Rhoton et al. 2002) and
soil temperature variations (Alletto et
al. 2011).
Both wheat and rice are exhaustive crops and the
fertility of the soil is affected. As the organic matter content of Pakistani
soils is already very low and it needs to be improved. Although the effects of
tillage systems on wheat performance in RWS are well reported; however, the
effects of winter cover crops on soil properties and wheat performance under
varying tillage systems are not reported. Therefore, this two-year field study
was designed with the hypothesis that cover crops may improve the fertility
status of soil and wheat performance under conventional and conservation
tillage systems.
Materials and Methods
Experimental site
This
two-year field experiment was conducted at Adaptive Research Farm, Gujranwala
(32.18°N, 74.19°E), Punjab, Pakistan. Physico-chemical
properties of the experimental soil are given in Table 1. The weather data of
both years 2017–18 are 2018–19 are given in Fig. 1.
Crop husbandry
Table 1: Pre-analysis of soil in both
years
|
Characteristics |
Unit |
Value |
||
|
2017–18 |
2018–19 |
|||
|
Sand |
% |
10 |
10 |
|
|
Silt |
% |
25 |
25 |
|
|
Clay |
% |
65 |
65 |
|
|
Textural Class |
Clay |
|||
|
Aggregate stability |
% |
21.545 |
22.108 |
|
|
Bulk density |
0–15 cm |
Mg m-3 |
1.70 |
1.67 |
|
15–30 cm |
1.77 |
1.75 |
||
|
Porosity |
0–15 cm |
m3 m-3 |
0.360 |
0.365 |
|
15–30 cm |
0.342 |
0.344 |
||
|
Organic matter |
0–15 cm |
% |
0.52 |
0.54 |
|
15–30 cm |
0.47 |
0.46 |
||
|
WHC |
0–15 cm |
m3 m-3 |
0.252 |
0.289 |
|
15–30 cm |
0.240 |
0.255 |
||
WHC= water holding capacity
%201265-1272_files/image002.png)
Fig. 1: Mean maximum and minimum temperature and total rainfall
during the growing season of wheat at the experiment site in both years (A= 2017-18, B=2018-19)
The rice
crop was sown in the first week of July by the direct-seeded method. The cover
crops were sown on the 5th of October at the physiological maturity
of rice crop. After the harvest of rice crop by using combine harvester, the
standing cover crops and the rice crop remnants were incorporated in the field
by plowing and wheat was sown. The cover crops at this stage were 1.5 months
old. The treatments of cover crops were control (no cover crop), crimson clover
(Trifolium incarnatum L.), alfalfa (Medicago sativa L.), hairy vetch (Vicia
villosa Roth), sweet clover (Melilotus
officinalis (L.) Pall.)
and Egyptian clover (Trifolium
alexandrinum L.), while the tillage methods for wheat were
zero-till, conventional tillage and deep tillage. The seed of cover crops was
purchased from local market of seed, Dijkot road, Faisalabad, Pakistan. Cover
crops were sown using a seed rate of 9 kg ha-1. The experiment was
conducted following a randomized complete block design with factorial
arrangement having three replications. The net plot size was 5 m × 5 m for each
replication. Wheat crop was sown on 26 November and 22 November and was harvested on 15 April 13 April during first and sec crop
seasons, respectively. For the zero-tillage the soil after the harvesting of
rice was not disturbed and the wheat was sown by direct seeding in post rice soil with a manually operated ZT drill.
For the conventional sowing method of wheat, field was cultivated four times to
the depth of 8–10 inches with a cultivator followed by use of rotavator
levelling. The crop was sown mechanically using happy seeder drill. In deep
tillage, the soil was plowed twice by the mould board
plow followed by use of rotavator. The field was then cultivated four times to the depth of 15–18 inches with a cultivator followed
by levelling. Crop was then sown mechanically using
happy seeder drill. Seed of wheat variety,
procured from the Punjab Seed Corporation, was seeded at a seed rate of 125 kg
ha-1 in all treatments. Fertilizers were applied at 85, 50 and 60 kg
ha-1 nitrogen (N), phosphorus (P) and potassium (K) using urea (46%
N), di-ammonium phosphate (DAP; 18% N, 46% N) and potassium sulphate (50% K). The total amount of P and K and half
of N fertilizers were applied as basal dose at sowing while remaining half of N
was applied sec irrigation. In total, three irrigations were applied to save
crop from moisture stress. A selective herbicide Buctril-M (bromoxynil + MCPA)
was applied for weed control (at 750 ml ha) 30 days after sowing (DAS). Wheat
was harvested by using combine harvester in both years.
Data collection and soil sampling
At harvest
maturity stage, tillers were counted manually from each replication from a unit
area (1 m × 1 m). After tiller count, these tillers were harvested manually,
and threshed. From each plot five central rows were manually harvested
for grain yield and straw yield and the data were recorded by electric balance
in kilograms and expressed as kg ha-1 after separating the grains
from straw using mini thresher while the rest of crop was harvested by combine
harvester. Three samples of 1000 grains were taken from each seed lot to
record 1000-grain weight using electric balance. Biological yield is the sum of
grain yield and straw yield.
For leaf area, healthy mature
leaves were collected 60 DAS. Leaf area was taken by multiplying leaf length, width
and correction factor. The correction factor to calculate the leaf area for
wheat is 0.8. Leaf area index was calculated using the formula of Dwyer and
Stewart (1986). Leaf area duration (LAD) and net assimilation rate (NAR) were
recorded following to Hunt (1978) 60 DAS.
Table 2: Residual effect of cover crops
and tillage methods on soil bulk density, water holding capacity and soil
organic matter
|
Cover crops |
2017–2018 |
2018–2019 |
||||
|
ZT |
CT |
DT |
ZT |
CT |
DT |
|
|
Bulk density (mg m-3) |
||||||
|
Control |
1.70a |
1.61b |
1.57c |
1.65a |
1.54b |
1.53cd |
|
Crimson clover |
1.57cd |
1.53f |
1.50h |
1.52de |
1.48g |
1.46ij |
|
Alfalfa |
1.52fg |
1.49h |
1.45i |
1.45gh |
1.43h-j |
1.39kl |
|
Hairy vetch |
1.61b |
1.54ef |
1.53fg |
1.57bc |
1.46fg |
1.47fg |
|
Sweet clover |
1.56c-e |
1.55d-f |
1.51gh |
1.50de |
1.50ef |
1.46g-i |
|
Egyptian clover |
1.48h |
1.44i |
1.42j |
1.40jk |
1.39lm |
1.38m |
|
LSD value at P
≤ 0.05 |
0.025 |
0.023 |
||||
|
Water holding capacity (m3 m-3) |
||||||
|
Control |
0.298ij |
0.298ij |
0.290j |
0.309ij |
0.308ij |
0.301j |
|
Crimson clover |
0.308e-h |
0.303f-i |
0.300hi |
0.315e-h |
0.312f-i |
0.311hi |
|
Alfalfa |
0.334a |
0.321bc |
0.322b |
0.344a |
0.330bc |
0.330b |
|
Hairy vetch |
0.309e-g |
0.312c-e |
0.312c-e |
0.315e-g |
0.324c-e |
0.321c-e |
|
Sweet clover |
0.302g-i |
0.319b-d |
0.299i |
0.308g-i |
0.327b-d |
0.307i |
|
Egyptian clover |
0.320b-d |
0.313b-e |
0.312d-f |
0.331b-d |
0.325b-e |
0.323d-f |
|
LSD value at P
≤ 0.05 |
8.83 |
8.81 |
||||
|
Organic matter (%) |
||||||
|
Control |
0.51hi |
0.47j |
0.41k |
0.55hi |
0.50j |
0.44k |
|
Crimson clover |
0.63b |
0.56d-f |
0.52hi |
0.69b |
0.61d-f |
0.57hi |
|
Alfalfa |
0.59cd |
0.54f-g |
0.50i |
0.66cd |
0.58f-h |
0.54i |
|
Hairy vetch |
0.55e-g |
0.50i |
0.47j |
0.60e-g |
0.54i |
0.52j |
|
Sweet clover |
0.57de |
0.52hi |
0.47j |
0.63de |
0.57hi |
0.53j |
|
Egyptian clover |
0.71a |
0.61bc |
0.53gh |
0.74a |
0.66bc |
0.58gh |
|
LSD value at P
≤ 0.05 |
0.027 |
0.026 |
||||
Means sharing the same letters, within rows and columns for each trait
during a year, don’t differ significantly at P ≤ 0.05
ZT= Zero tillage, CT= Conventional tillage, DT= Deep tillage
Statistical analysis
Experimental
data were analyzed by analysis of variance (ANOVA) techniques using statistical software IBM SPSS v. 21.
Before applying two-way ANOVA, data were checked for normality and were found
to be normally distributed. Tukey Honestly
Significant Difference (HSD) test at P ≤ 0.05 was used for mean
separation (Steel et al. 1997).
Results
Soil properties
The tillage
methods and cover crops significantly affected the soil properties (bulk
density, WHC and SOM) (Table 2). The interaction of tillage methods and cover
crops was also significant. All the cover crops improved the above soil
properties than the control. Tillage reduced the soil bulk density compared
with zero tillage. In this regard, the most reduction in bulk density was noted
in the deep tillage during the both years. Minimum soil bulk density was noted
in deep tillage with Egyptian clover as a cover crop during both years that was
similar to conventional tillage with Egyptian clover as a cover crop during sec
growing season (Table 2). The interaction of tillage methods and cover crops on
WHC was significant interaction. From the cover crops, alfalfa was the most
effective in improving the WHC during both years (Table 2).
For soil organic matter, zero tillage method had strong
interaction with cover crops to improve it. All the cover crops showed better
results except hairy clover and sweet clover which gave non-significant
results. Egyptian clover was more
effective in improving the organic matter. Soil organic matter was improved
significantly in both years. Zero-till was better method than conventional and
deep tillage method to increase the SOM in wheat for both years (Table 2).
Net assimilation rate and Leaf area duration
Net
assimilation rate (NAR) and leaf area duration (LAD) were significantly
improved in both the years. The interaction of tillage methods and cover crops
was significant. All the tillage methods improved the NAR, but it was
conventional tillage which gave better results in this regard. All the cover
crops performed better than control in both the years but in the sec year sweet
clover did not improve the NAR whereas alfalfa did not significantly improve
the NAR during the first year in the conventional tillage compared with control
(Table 3). Leaf area duration (LAD) increased significantly in both years and
the highest LAD was noted in conventional tillage with Egyptian clover as a
cover crop during both years that was similar to zero tillage with Egyptian
clover as a cover crop during sec growing season (Table 3).
Yield and related traits
Table 3: Residual effect of cover crops
and tillage methods on leaf area duration and net assimilation rate
|
Cover crops |
2017–2018 |
2018–2019 |
||||
|
ZT |
CT |
DT |
ZT |
CT |
DT |
|
|
Leaf area
duration (days) |
||||||
|
Control |
121.3j-l |
120.6l |
120.8kl |
123.9j-l |
123.4l |
123.6kl |
|
Crimson clover |
123.8f-h |
121.7e-g |
123.7g-i |
125.1f-h |
125.2e-g |
124.8g-i |
|
Alfalfa |
123.5cd |
124.8c |
122.6d-f |
126.4cd |
127.5c |
125.8d-f |
|
Hairy
vetch |
122.0i-k |
124.2f-h |
123.5i-k |
124.3i-k |
125.1f-h |
124.3ijk |
|
Sweet
clover |
124.7g-i |
124.4de |
121.7h-j |
124.9g-i |
126.1de |
124.5h-j |
|
Egyptian
clover |
125.8b |
126.5a |
125.3c |
127.9b |
129.3a |
127.0c |
|
LSD
value at P ≤ 0.05 |
0.79 |
|
|
0.84 |
|
|
|
Net assimilation
rate (g m-2 day-1) |
||||||
|
Control |
2.59j |
2.75f |
2.48l |
2.61j |
2.78f |
2.48l |
|
Crimson
clover |
2.65hi |
2.80e |
2.54k |
2.66hi |
2.82e |
2.56k |
|
Alfalfa |
2.86cd |
3.03b |
2.73fg |
2.90cd |
3.03b |
2.75fg |
|
Hairy
vetch |
2.69gh |
2.87d |
2.61ij |
2.70gh |
2.88d |
2.64ij |
|
Sweet
clover |
2.74fg |
2.92c |
2.67h |
2.74fg |
2.94c |
2.67h |
|
Egyptian
clover |
2.99b |
3.22a |
2.77ef |
3.01b |
3.25a |
2.80ef |
|
LSD
value at P ≤ 0.05 |
0.05 |
|
|
0.07 |
|
|
Means sharing the same letters, within rows and columns for each trait
during a year, don’t differ significantly at P ≤ 0.05
ZT= Zero tillage, CT= Conventional tillage, DT= Deep tillage
The cover
crops and tillage methods significantly improved the yield parameters (tillers,
grains per spike, 1000-grain weight, grain yield and harvest index (Table 4).
The interaction between cover crops and sowing methods was also significant.
The conventional tillage was better to improve the yield and related parameters
using Egyptian clover as cover crop in both years that was followed by the Egyptian clover (Table 4).
Economic analysis
Use of
cover crops increased the total cost than control but also improved the net
benefits and benefit-cost ration (BCR). The highest net benefits and BCR were
recorded from wheat planted with conventional tillage using Egyptian clover as
cover crop.
Discussion
Results of this two-year field study revealed that use of
cover crops substantially improved the soil physical properties, SOM, soil
water holding capacity and wheat yield under conventional and conservation
tillage systems (Tables 2–5). Cover crops and tillage methods decreased the
soil bulk density significantly. The tillage practices help to break the pan
created during cropping season which increase the pore volume and ultimately
reduce the soil bulk density. As the deep tillage method ploughed the soil
deeply than conventional and zero tillage method so bulk density was minimum in
deep tillage systems (Oquist et al. 2006; Jabro et al. 2008;
Shahzad et al. 2016). Lowering the soil bulk density can help in water
holding, deep rooting and more gaseous exchange in the soil. The soil bulk
density was highest in ZT while lowest was recorded in deep tillage (Table 3).
The minimum use of mechanical actions under ZT leads towards progressive
densification and minimized pore volume (Du et al. 2010; Jemai et al.
2012), which improves the soil bulk density (Xu and Mermoud 2001; Thomas et
al. 2007) due to soil compaction. Cover crops have significant interactions
with all the sowing methods to reduce the soil bulk density. Alam et al.
(2013) also claimed that adding biomass of cover crops into the soil could help
to increase the available water content within soil and reduce the bulk
density.
Soil organic matter was
improved more in zero tillage method than deep and conventional methods. In ZT
there is less soil disturbance, so the organic matter increases due to minimum
disturbance and exposure to decomposer and environment. Zero-tilled soils with
buildup of crop residues are enhanced in labile SOM at the surface, which has a
pronounced influence on soil structure by modifying aggregation (Beare et al. 1994; Lu et al. 1998). In ZT, crop residues accumulation on surface as mulch
effects water, energy and air exchange between the atmosphere and soil
ecosystem (Lobell et al. 2006). It is
difficult to improve the organic matter in conventional and deep tillage
methods (Hobbs et al. 2008) because in conventional and deep tillage
methods, the crop residues are in more access to decomposer and warm
environment. Cover crops residues also play role as mulch to soil to restore
more water. As the organic matter served as the porous agent and helpful in
improving the soil structure so, the increased organic matter also increased
the porosity and lowered the bulk density of the soil. The decrease in the bulk
density helped in improving the pore spaces in the soil. The increase in the
pore spaces helped to enhance the water retention ability of the soil. As there
were more micro pores in the soil so there were more chances to hold the water
and ultimately increase the water holding capacity.
Table 4: Residual
effect of cover crops and tillage methods on 1000-grain weight, tiller count,
yield and number
of grains per spike in the heading
|
Cover crops |
2017–2018 |
2018–2019 |
||||
|
ZT |
CT |
DT |
ZT |
CT |
DT |
|
|
Tiller count (m-2) |
||||||
|
Control |
568.0k |
571.3h-j |
555.3n |
569.6k |
572.6h-j |
556.4n |
|
Crimson clover |
572.3g-i |
574.3e-g |
562.6m |
573.7g-i |
575.7e-g |
565.7m |
|
Alfalfa |
577.3cd |
579.3c |
570.3ij |
578.5cd |
581.3c |
572.2ij |
|
Hairy vetch |
575.0ef |
575.6de |
565.2l |
576.6ef |
577.3de |
567.3l |
|
Sweet clover |
573.3f-h |
574.6ef |
569.3jk |
575.2f-h |
545.8d-f |
570.8jk |
|
Egyptian clover |
581.6b |
586.6a |
573.6e-g |
583.7b |
588.7a |
575.7e-g |
|
LSD value at P ≤ 0.05 |
2.25 |
2.26 |
||||
|
Number of grains per spike |
||||||
|
Control |
43.6k |
47.0h-j |
31.0n |
44.3j |
48.0g-i |
32.6l |
|
Crimson clover |
48.0g-i |
50.0e-g |
38.3m |
49.0f-h |
49.3e-g |
40.3k |
|
Alfalfa |
53.0cd |
55.0c |
46.0ij |
53.3c |
56.0b |
47.0hi |
|
Hairy vetch |
50.6ef |
51.3ed |
41.0l |
51.6cd |
51.3c-e |
41.3k |
|
Sweet clover |
49.0f-h |
50.3ef |
45.0jk |
50.0d-g |
51.3c-e |
46.0ij |
|
Egyptian clover |
57.3b |
62.3a |
49.3e-g |
57.5b |
64.0a |
50.3d-f |
|
LSD value at P ≤ 0.05 |
2.25 |
|
|
2.27 |
|
|
|
1000-grain weight (g) |
||||||
|
Control |
40.7ij |
42.4h |
39.6j |
41.5ij |
43.0h |
40.0j |
|
Crimson clover |
44.6fg |
46.7c-e |
41.9hi |
45.1fg |
47.6c-e |
42.6hi |
|
Alfalfa |
48.2c |
49.9b |
45.0f |
48.9c |
50.5b |
45.9f |
|
Hairy vetch |
41.9hi |
45.4ef |
43.2gh |
42.6hi |
46.1ef |
44.0gh |
|
Sweet clover |
46.5de |
47.4cd |
45.3ef |
47.4de |
48.1cd |
45.9ef |
|
Egyptian clover |
50.1b |
52.3a |
47.1cd |
50.7b |
53.2a |
47.8cd |
|
LSD value at P ≤ 0.05 |
1.50 |
|
|
1.55 |
|
|
|
Grain yield (kg ha-1) |
||||||
|
Control |
4080.4ij |
4248.4h |
3968.5 |
4208.9ij |
4376.8h |
4096.9j |
|
Crimson clover |
4465.8fg |
4673.2c-e |
4195.7hi |
4594.2fg |
4801.7c-e |
4324.1hi |
|
Alfalfa |
4814.9c |
4982.8b |
4498.7f |
4943.3c |
5111.3b |
4627.1f |
|
Hairy vetch |
4195.7hi |
4538.2ef |
4327.5gh |
4324.1hi |
4666.7ef |
4455.9gh |
|
Sweet clover |
4650.2de |
4739.1cd |
4534.9ef |
4778.6de |
4867.5cd |
4663.4ef |
|
Egyptian clover |
5009.2b |
5219.9a |
4706.2cd |
5137.6b |
5348.4a |
4834.6cd |
|
LSD value at P ≤ 0.05 |
148.76 |
|
|
148.84 |
|
|
Means sharing the same letters, within rows and columns
for each trait during a year, don’t differ significantly at P ≤
0.05
ZT= Zero tillage, CT= Conventional tillage, DT= Deep
tillage
Table 5: Economic analysis of wheat production by using cover crops
|
Treatments |
Total cost (US$
ha-1) |
Gross income
(US$ ha-1) |
Net benefits
(US$ ha-1) |
Benefit-cost
ratio |
||||||||
|
ZT |
CT |
DT |
ZT |
CT |
DT |
ZT |
CT |
DT |
ZT |
CT |
DT |
|
|
2017–18 |
||||||||||||
|
Control |
308.7 |
310.4 |
310.4 |
834.5 |
840.1 |
825.5 |
525.8 |
529.7 |
515.1 |
2.70 |
2.70 |
2.65 |
|
Crimson clover |
310.5 |
311.9 |
311.9 |
928.1 |
935.7 |
923.3 |
617.6 |
623.8 |
611.4 |
2.98 |
3.00 |
2.96 |
|
Alfalfa |
311.9 |
313.6 |
313.6 |
955.8 |
965.4 |
948.4 |
643.9 |
651.8 |
634.8 |
3.06 |
3.07 |
3.02 |
|
Hairy vetch |
311.6 |
312.3 |
312.3 |
912.3 |
920.6 |
904.7 |
600.7 |
608.3 |
592.4 |
2.92 |
2.94 |
2.89 |
|
Sweet clover |
310.1 |
311.7 |
311.7 |
916.7 |
925.3 |
910.2 |
606.6 |
613.6 |
598.5 |
2.95 |
2.96 |
2.92 |
|
Egyptian
clover |
311.4 |
313.3 |
313.3 |
974.6 |
980.6 |
967.9 |
663.2 |
667.3 |
654.6 |
3.12 |
3.12 |
3.08 |
|
2018–19 |
||||||||||||
|
Control |
308.2 |
310.4 |
310.4 |
835.9 |
840.3 |
828.6 |
527.7 |
529.9 |
518.2 |
2.71 |
2.70 |
2.66 |
|
Crimson clover |
309.6 |
311.7 |
311.3 |
931.7 |
937.2 |
928.1 |
622.1 |
625.5 |
616.8 |
3.00 |
3.01 |
2.98 |
|
Alfalfa |
311.2 |
313.5 |
312.9 |
960.2 |
970.6 |
957.4 |
649.0 |
657.1 |
644.5 |
3.08 |
3.09 |
3.05 |
|
Hairy vetch |
311.1 |
312.3 |
312.1 |
919.3 |
918.2 |
907.6 |
608.2 |
605.9 |
595.5 |
2.95 |
2.94 |
2.90 |
|
Sweet clover |
309.3 |
311.7 |
311.4 |
914.8 |
922.4 |
911.8 |
605.5 |
610.7 |
600.4 |
2.95 |
2.95 |
2.92 |
|
Egyptian
clover |
310.8 |
313.0 |
312.7 |
977.2 |
984.3 |
975.7 |
666.4 |
671.3 |
663.0 |
3.14 |
3.14 |
3.12 |
ZT= Zero tillage,
CT= Conventional tillage, DT= Deep tillage, 1 US$= 160.6 PKR
As the cover crops and tillage
practices improved the soil properties and enhanced the nutrients in the soil
by adding the soil organic matter so, the agronomic parameters were also
improved. As there were more nutrients than the control so the agronomic
parameters improved significantly in all the treatments than the control.
Residual effect of cover crops and conventional tillage was also clear in improving
the LAD, LAI, NAR and wheat yield (Vazin et
al. 2010; Haider et al. 2016).
The residual effect of cover crops helped to increase the LAD and NAR for the
crop so there was increase in the growth of main crop than the weed (Uchino et al. 2012). The cover crops and
tillage methods also improved the grain weight and yield (Table 5). The cover
crops residues served as mulch and helped in water retention and to increase
the yield because mulching is a viable management practice for improving crop
yield and water (Jabran et al. 2016).
Profitability principally
depends upon the input cost involved and the economic yield. Increase in the
profitability is the single most important factor, which may attract the
growers to adopt the conservation tillage systems. The maximum net benefits,
benefit–cost ratio and highest method productivity were obtained in
conventional tillage using Egyptian clover as cover crop followed by alfalfa as
cover crop in conventional tillage. The improved profitability in wheat may be
due to better grain yield (Table 5) and less input cost, which resulted in more
profit margins (Farooq and Nawaz 2014).
Conclusion
Tillage systems and cover
crops had significant effect on wheat productivity due to their noteworthy
impact on soil physical properties and organic matter. Conventional tillage
along with Egyptian clover as cover crop help to improve the organic matter,
moisture level and to reduce the crust pan which ultimately help wheat crop to
grow well leading to its higher productivity and net returns.
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