Synthetic and organic mulching and nitrogen effect on winter wheat (Triticum aestivum L.) in a semi-arid environment

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Abstract

Field experiments were conducted in 2002–2003 and 2003–2004 to evaluate the relative performance of synthetic (black polyethylene) and organic (paddy husk and straw) mulches on soil and plant water status vis-a-vis N uptake in wheat in a semi-arid environment of India. Scope of better utilization of soil moisture was documented through all the mulches, especially during initial crop growth stages, when the moisture content was 1–3% higher in mulches. Soil temperature was more moderate under organic mulches. Paddy husk recorded significantly higher plant biomass, while the effect of mulching in enhancing root growth was clearly documented. Organic mulches produced more roots (25 and 40% higher root weight and root length densities compared to no-mulch) in sub-surface (>0.15 m) layers, probably due to greater retention of soil moisture in deeper layers and relatively narrow range of soil temperature changes under these systems. Incremental N dose significantly improved all the plant parameters in both mulch and no-mulch treatments. Grain yield was 13–21% higher under mulch and so with increasing N levels. Nitrogen uptake was higher in organic mulches and also with higher N doses, while polyethylene mulch showed mixed trend. Mulches were effective in reducing 3–11% crop water use and improved its efficiency by 25%. Grain yield and biomass were well-correlated with leaf area index (r = 0.87 and 0.91, respectively) and water use was better correlated with root length than its weight. Results indicated substantial improvement in water and N use efficiency and crop growth in wheat under surface mulching, and the organic mulches, especially rice husk performed better than synthetic mulches.

Introduction

Wheat (Triticum aestivum L.), the second most important rabi cereal crop in India, has been witnessing significant yield stagnation and decline since 1999 and is presently showing an average yield of 4–5 Mg ha−1 with recommended (120 kg N ha−1) dose of fertilizer (Duxbury et al., 2000, Yadav et al., 2000, Nagarajan, 2005). With no chance of expansion in area and little scope for further intensification of wheat based cropping systems, increase in yield through better crop management might be the only option. Being highly sensitive to water stress, the yield of wheat with restricted water supply is substantially low and improving the water use efficiency may significantly increase the yield in such situations (Kalra et al., 2007, Chakraborty et al., 2008). The availability of water for irrigated wheat (water requirement of high yielding variety normally varies between 400 and 500 mm) is also progressively becoming limited, even in high yielding areas of Punjab, Haryana and western Uttar Pradesh. In coming years, the growth in agricultural productivity vis-a-vis food security in India will increasingly depend on improved utilisation of rainfed regions, which might cater for the country's 2nd Green Revolution. As water is limited, these regions must adopt suitable water conserving techniques in order to improve the water use efficiency and thereby increasing the productivity. Mulching has been proved to be beneficial in conserving moisture and increasing productivity in wheat (Verma and Acharya, 2004a, Verma and Acharya, 2004b, Li et al., 2005, Huang et al., 2005, Rahman et al., 2005, Chakraborty et al., 2008). The recommended N application rate under mulch situation is 120 kg ha−1, which is likely to be different under the modified moisture regime induced by mulching. So far, little information is available on comparative effects of various types of mulches and nitrogen response in wheat under the semi-arid environment of India. Keeping these in background, field experiments were carried out in a sandy loam soil in semi-arid environment of Delhi, India, to study the effect of different types of mulches along with nitrogen application rates on growth and yield of winter wheat and its water and nitrogen use efficiencies.

Section snippets

Study area

Field experiments involving mulching during 2002–2003 and 2003–2004 were conducted at the Indian Agricultural Research Institute Research Farm, New Delhi, India (28°37′N, 77°9′E, 228.7 m amsl). The soil type was sandy loam (Typic Haplustept), non-calcareous and neutral in reaction (pH 7.5) and low in soil organic matter content (0.2–0.5 g kg−1). Brief information on the soil physical properties of the experimental field is presented in Table 1. The climate is semi-arid. Average day-time

Soil moisture as influenced by mulching

Pre-sowing irrigation was applied to bring uniformity in soil moisture in the profile. Moisture content in the experimental field was recorded as 15 (±2)% at sowing, which ensured identical germination in all plots; variation of moisture between mulch and no-mulch treatments was noticed with time. During first year (2002–2003) of the experiment, on 34 DAS (irrigation was given on 30 DAS), soil moisture in all plots maintained near field capacity values (∼0.24 m3 m−3) up to 0.45 m, and a little

Discussion

The moisture profile suggested that during the initial stage of crop growth, the moisture was better conserved under mulched plots. As most of the roots were within upper 0.15 m soil, the conserved moisture could be more beneficial in growth and early establishment of crops, as evidenced by the growth parameters of wheat. At later stage of crop growth, the effect of mulch marginally reduced, probably because of reduced evaporation from the soil due to crop canopy coverage over the ground, but

Conclusion

Organic mulches provided better soil water status and improved plant canopy in terms of biomass, root growth, leaf area index and grain yield, which subsequently resulted in higher water and nitrogen uptake and their use efficiencies. Greater nitrogen application also resulted in better crop growth. A significant interaction of mulching and nitrogen was also observed for grain yield of wheat. It may be concluded that organic mulch (paddy straw @6 or paddy husk @9 Mg ha−1) application with 120 kg N ha

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