Water use efficiency of green gram (Vigna radiata L.) impacted by paddy straw mulch and irrigation regimes in north-western India

Highlights

• Paddy straw mulch (6 t ha ^-1) and increased irrigation frequency improved vegetative growth.

• Lesser irrigations (3) along with mulch resulted in comparable yield with supplementary irrigations (6−7) without mulch.

• The crop water use was maximum for non-mulch treatment and higher irrigation frequency.

• The BPWP and WUE was higher for 6 t ha⁻¹ mulch application and reduced irrigation frequency.

Abstract

A multilocation field experiment was conducted at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University (PAU), Ludhiana and PAU, Regional Research Station (RRS), Bathinda, during summer 2019. The experiment was conducted in RCBD with 15 treatment combinations with 3 replications. The treatments comprised of 3 mulch levels i.e., M₀, M₆, and M₁₂ i.e., no mulch, 6 and 12 t ha⁻¹, respectively, and 5 irrigation schedules i.e., I₁₀, I₂₀, I₃₀, and I₄₀ with 10%, 20%, 30% and 40% depletion of available soil water (ASW), respectively, and I_R (PAU recommendation as 4 irrigations). The growth parameters (plant height, dry matter accumulation and leaf area index), yield attributing characters namely pods per plant, number of seeds per pod and thousand-grain weight, seed and straw yield were significantly higher in M₁₂ than M₆ and no mulch (M₀). The growth parameters, yield attributes, seed and straw yield were significantly higher for I₁₀ due to increased irrigation frequency (5–6 irrigations). Both M₀I₁₀ (seven irrigations without mulch) and M₆I₃₀ (3 irrigations with straw mulch (6 t ha⁻¹)) treatments observed comparable seed yield (1.06 t ha⁻¹). Therefore, the substantial increase in seed yield with lower crop water use with the usage of straw mulch saves a considerable amount of water. Subsequently, the use of 6 t ha⁻¹ of straw mulch with 3 irrigations (30% depletion from available soil water) facilitated a higher seed yield. The crop water use (CWU) was highest for M₀ as due to bare soil, resulted in more evapotranspiration. The bio-physical productivity (BPWP) and water use efficiency was found to be maximum for mulch treatments. The I₁₀ reported maximum CWU, whereas, Bio-physical water productivity (BPWP) were higher for I₄₀ treatment where only one irrigation was given in this treatment. The WUE was maximum in I₃₀ treatment at Ludhiana and in I₂₀ at Bathinda location.

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.