Rainfall
In the first crop year, the accumulated rainfall from September to June was 195.12 mm, with high variability in distribution. This growing season was considered as dry compared at the medium of long term (355 mm) ; June was the rainiest month with a rainfall of 55.5 mm and it coincided with the grain ripening stage. There was no rain in March and very little rainfall in April and May and it coincided with the third leaf stage and the grain formation stage.
The cumulative rainfall per second year of experimentation (2017/2018) was 419.2 mm. The months of March, April and May recorded a higher rainfall during second year. This period coincided with the critical growth stage of wheat crop. The total grain yield recorded was 4.33 t/ha in second year and it was quite higher as compared with that of first year yield of 0.83 t/ha. In rain-fed agriculture, accumulated rainfall affects crop growth and crop yield.
There was higher rainfall and better distribution in the second year as compared to first year (Fig 1). This will help us to better understand the behavior of wheat crop under different plowing situations under varying climatic conditions.
Stored water in the soil (water profile H%)
In the semi-arid areas cumulative rainfall directly affect the soil water content. Further the humidity was higher in the second agricultural season as compared to the first year (Fig 2). During initial stage of crop growth, the tillage practices
viz., no-till and minimum tillage, recorded relatively high soil water contents at 0-20 cm soil profile as compared to conventional tillage recording 23%, 23% and 22% soil moisture, respectively. The soil water storage rate in the three tillage techniques too decreased until the third leaf stage.
The water content increased in soil after receipt of rain at third leaf stage to first node, low rainfall decreased soil water content to grain maturity. The NT and MT practices stored more soil water than CT practices by 2% to 4%. This period coincided with ear formation stage of crop. At 20-40 cm profile, CT registered least soil water content as compared to NT and MT during most of vegetative phase with 2% different maximum difference. The MT registered a rise in water content between tillering stage and beginning of boot stage. So NT was higher in the other stages. Soil water content was almost equal in two depths 0-20 and 20-40 cm under different tillage practices. At the seeding stage, NT registered high moisture content as compared to MT and CT. At the second and the third leaf stage, NT registered a decline in soil water content as compared to CT and MT, which increased during this period.
Water use efficiency
about the water use efficiency between two years recorded significant difference. However there was no significant difference among tillage operations
viz., NT, MT and CT (Fig 3).
Grain yield water use efficiency WUEGy was higher in no-till (NT) during both the seasons with 5.775 and 10.138 kg/ha/ mm, respectively. Minimum tillage (MT) recorded 3.638 and 9.854 kg/ha/mm, respectively for the first and second season. The conventional tillage (CT) recorded the least grain yield water use efficiency of 3,160 and 8.203 kg/ha/mm, respectively for the first and second season (Fig 4).
Water use efficiency for above ground biomass production (WUEbio) for CT were 6,269 and 9,675 kg/ha/mm for MT, 6.007 and 9.326 kg/ha/mm and for NT were 5.508 and 8.704 kg/ha/mm.
Yield parameters and yield
Thousand-kernel weight
The thousand-kernel weight recorded significant differences in NT (36.09 g and 50.36 g) as compared to MT (30.93 g and 46.81 g) and CT (28.31 g-45.05 g) in the first and second season, respectively (Fig 5).
Gain yield
The grain yield and biomass production between two years recorded significant differences (Fig 6). However there were no significant differences between the tillage operations
viz., NT, MT and CT.
The no tillage (NT) recorded higher yield (1.072 and 4.71 t/ha) as compared to MT (0.76 and 4.53 t/ha) and CT (0.67 and 3.76 t/ha) in first and second season, respectively. The average crop yield was very low (0.94 t/ha) during first season.
Harvest index
The harvest index recorded significant differences in NT (0.95 and 1.20) as compared to MT (0.60 and 1.04) and CT (0.56 and 0.90) in first and second season, respectively (Fig 7).
Correlation among characteristics
In the first season the water use efficiency and grain yield showed a high positive correlation with 1000 kernel weight, grain yield and harvest index and a high negative correlation with number of spikes per m². Grain yield showed a high positive correlation with 1000 kernel weight and harvest index and a strong negative correlation with number of spikes per m
2. The 1000 kernel weight showed a high positive correlation with harvest index and a high negative correlation with number of spikes per m² and harvest index (Table 1).
However, in the second growing season, the water use efficiency grain yield showed a high positive correlation with 1000 kernel weight, grain yield and harvest index. Water use efficiency biomass production showed a high positive correlation with number of spikes per m
2 and a strong negative correlation with 1000 kernel weigh. However grain yield showed a high positive correlation with 1000 kernel weight and harvest index. The 1000-kernel weigh showed a high positive correlation with harvest index and harvest index showed a negative correlation with number of spikes per m
2 (Table 2).
Many studies have been conducted to compare and evaluate the effects of different tillage operations on soil moisture and crop behavior under conservation agriculture.
The cumulative rainfall recorded from crop sowing to harvest was 195.12 mm in 2016/17 and 419 mm in 2017/18. The deference was very clear and the first cropping season being a dry year, recorded lower productivity. In the first season zero and minimum tillage operations registered high soil water storage as compared to conventional tillage. It is reported that conservation tillage plays a significant role in improving soil moisture availability, especially under low rainfall conditions (
Ghosh, 2015). The no tillage (NT) is proposed as a promising strategy to improve soil and water conservation, reduce input costs and to increase crop yield
(Channafi et al., 2011). The results of
Sun et al., (2018b) indicated that both deep ploughing and sub-soiling significantly increase soil water storage not only during fallow period, but also during growing season.
The grain yield and water use efficiency of grain yield were high under no and minimum tillage operations.
Benniou (2012) reported that conservation agriculture (CA) increases soil water balance attributes as compared to conventional plowing Furthermore this system often resulted in higher water productivity as compared to conventional tillage system.
The results of second season indicated that wheat can be grown successfully under conservation tillage systems with yields equal or higher than those of conventional tillage in high rainfall condition.
Many of studies also reported that soil water use efficiency was higher under no tillage than the conventional tillage and this indicated that water was obsorbed from the soil by crops. It was observed that crops in conservation cultivation tolerate droughts and recessions in rainfall. Often yields are higher under dry season conditions in conservation tillage (
Alheeti, 2019;
Lampurlanés et al., 2016;
Thierfelder and Wall, 2009;
Mrabet, 2002).