Water use efficiency of green gram (Vigna radiata L.) impacted by paddy straw mulch and irrigation regimes in north-western India
Introduction
In the Indian northern plains, it is commonly observed that the field remains vacant till the onset of the monsoon. So, short duration crop which can fit in the crop sequence of rice-wheat has immense importance. Thus, the green gram bean (Vigna radiata L.) can be considered as the best candidate for the short window period after the harvest of the wheat. The green gram being the short duration crop (60 days) have a higher yield and attracts the farmers of Punjab as well as of the whole Indo-Gangetic Plains. The seeds of the green gram are highly nutritious containing 2.5–3.0 times higher protein content than cereals (Kumar et al., 2016). Green gram is resistant to drought and shade conditions as well as to low fertility. The green gram crop can restore soil fertility by biological nitrogen fixation (Ram et al., 2016) and so adds value in the rice-wheat rotation. Usually, there are two seasons for the sowing of green gram i.e., the summer season and the kharif season, for which the yield of green gram bean is higher as compared to the kharif season crop. The reason behind the lower yield of kharif season green gram is the concurrence with the monsoon and so higher infestation of diseases and insect-pest attack, whereas, the short duration varieties of summer green gram bean are available (Yadav and Singh, 2014). The crop of green gram bean is sown in the summer season which is characterized by harsh temperature conditions and low relative humidity, so the frequent application of irrigation is very essential for the growth and development of the crop (Singh, 2005).
Irrigation is termed as a key driving facet that affects water and nutrient dynamics in the plant’s root zone (Li et al., 2020). So, the major concern is the restoration of the fertile conditions of the soil with the rationalized use of water (Kaur, 2014). If the irrigation is limited at critical stages of the crop, it may drastically lower yields. So excess or inadequate water may unswervingly affect crop growth. So, increasing water productivity is an imperative practice lesser amount of water perceptively for obtaining higher yields. Henceforth, innovative irrigation practices help in enhancing water use efficiency, thereby enhancing the economic viability and environmental sustainability of the irrigation system (Levidow et al., 2014). Consequently, agronomic intervention like mulching proves to be a practical solution for maintaining the optimum soil thermal and moisture regimes (Ranjan, 1982) and ultimately higher crop yields (Sekhon et al., 2020). After the harvest of the paddy straw, farmers have paddy straw in abundance and usually being burnt in the field which pollutes the environment. Thus, using paddy straw for mulch in various field crops as well as vegetables can unravel the menace. Further, it is best organic mulch which in addition to the paddy straw mulch adds organic matter to the soil after its decomposition. The mulch application helps in the blockage of the transportation of the vapors from the soil surface by acting as a barrier to the soil and altering the net radiation arriving at the soil surface. It also helps in the suppression of the growth of the weeds, moderating the soil surface temperature, modifying the microclimatic conditions and helps in prevention of soil erosion (Kaur and Bons, 2017). Bunna et al. (2011) reported that paddy straw mulching helps in the tying up of soil nitrogen and the promotion of nitrogen in leguminous crops like green gram. Hence, it is hypothesized that with the application of mulch, a lesser number of irrigations are required by the crop. Keeping this in the view, the present study was undertaken with the objective to investigate the effect of paddy straw mulching and irrigation regimes on the growth and productivity of green gram. Secondly, to compute the water use and water productivity of green gram under various paddy straw mulch levels and irrigation regimes.
Section snippets
Experimental site
The experiment was carried out at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University (PAU), Ludhiana and PAU, Regional Research Station (RRS), Bathinda, during summer 2019. These two stations were observed due to the varied weather conditions for studying irrigation and mulching effects. The experimental site of Ludhiana is situated at an altitude of 247 m above mean sea level, with a latitudinal extent of 30°56′15″ N and a longitudinal extent of 75°52′45″ E. The
Growth parameters
The growth parameters such as the plant height, dry matter, and leaf area index (LAI) significantly varied with the mulch levels and irrigation regimes (Table 6). The plant height was 6.96% and 4.92% higher for M6 than M0 and M12, respectively for Ludhiana. However, the increase was 21.75% and 0.78% higher for M6 than M0 and M12, respectively for Bathinda. The dry matter accumulation was significantly higher for M6 and it was 18.56% and 8.19% higher than M0 and M12, respectively for Ludhiana.
Discussion
The dwindling irrigation resources and underground saline water in India, particularly in the southwest region of Punjab, enforce to ponder about water conservation and management. The farmers are buoyant to amplify cropping intensity for higher returns. So, it is our accountability to take care of our natural resources. The burning of paddy straw mulch after the harvest of the crop is widespread throughout rice-growing states. So, the use of paddy straw mulch for water conservation is of ample
Conclusion
Application of rice straw mulch at 6 t ha−1 conserved water and resulted in a higher pod set per plant and higher seed yield. The equivalent seed yield was observed under no mulch and 7 irrigations (10% depletion from available soil water) and straw mulch along with only 3 irrigations (30% depletion from available soil water). Also, recommended schedule (four irrigations) gave a comparatively lower yield than 30% depletion from available soil water irrigations in conjunction with straw mulch.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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