Nutrient Dynamics in Grain Amaranth and Competing Weeds under Different Weed Management Practices
Abstract
Afield experiment entitled "Effect of different post emergent herbicides on growth and yield of grain amaranth (Amaranthus caudatus L.)" was conducted at M block, field unit of AICRN on Potential Crops, University of Agricultural Sciences, Bengaluru during Kharif 2020. The experiment consisted of eight treatments which includes the application of five early post emergent herbicides (Fenoxaprop-p-ethyl, Quizalofop ethyl, Clomazone, Propaquizafop and Cyhalofop butyl), one manual weeding at 4 WAS, weed free check and weedy check which were replicated thrice in RCB design. Major weeds observed in the experimental plot were Cyperus rotundus, Cynodon dactylon, Echinochloa colona, Eleusine indica, Ageratum conyzoides, Alternanthera spinosa and Borreria articularis. Application of Quizalofop ethyl 5% EC at 50 g a.i. ha⁻¹ recorded significantly higher grain amaranth yield (1896 kg ha⁻¹), net returns (Rs. 68,178 ha⁻¹) and B:C ratio (2.56) which was on par with Propaquizafop 10% EC at 12 g a.i. ha⁻¹ (1805 kg ha⁻¹, Rs.63,524 ha⁻¹ and 2.38, respectively) without any phytotoxic effect on grain amaranth crop. However, weedy check recorded significantly lower grain yield (1005 kg ha⁻¹), lower net returns (Rs.25,731 ha⁻¹), lower B:C ratio (1.05) and higher weed index (51.29%) compared to other treatments. Similarly, nitrogen, phosphorus and potassium uptake by grain amaranth crop at harvest was significantly higher with early post emergent application of Quizalofop ethyl 5% EC at 50 g a.i. ha⁻¹ (74.1, 42.77 and 49.30 kg ha⁻¹, respectively) and lower in weedy check (30.44, 37.13 and 23.97 kg ha⁻¹, respectively).
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Introduction
Grain amaranth (Amaranthus caudatus L.)is a nutri-rich potential crop with C4 pathway, quick growing, broadleaved and multipurpose crop which can be grown for grain, leafy vegetable, ornamental and forage purpose. It is a warm season crop belongs to Amaranthaceae family and characterized as a plastic plant due to its high adaptability to drought, heat stress, high soil acidity and salinity. It is often called as Chaulai, Batu, Bhabhri, Harave, Keere, Marsha, Rajakeera, Sawal and Ram Dana in India.
Presently, it is mainly cultivated and consumed in India, Nepal, China, Indonesia, Malaysia; whole of Central America, Mexico, Southern and Eastern Africa. In India, grain amaranth is mostly cultivated in Himalayan region at higher and lower hilly regions as apure crop with some mixed cropping pattern too. This crop especially grown in few parts of Gujarat, Maharashtra and in various parts of Uttarakhand. In Gujarat, the Banaskantha district have approximately an area of 10,000 ha where this future potential crop replaced wheat and potato due to increasing problem of water scarcity. In Karnataka, grain amaranth is being grown by tribal communities in BRhills (Biligiri Rangana) of Chamarajnagara district. The statistical data on area and production in India is lacking. However, it is estimated to be grown in about 40-50 thousand ha (Raiger et al., 2009). Grain amaranth is very susceptible to weeds during its early growth period and it grows slowly after germination for the first few weeks and hence it is very susceptible to weed competition (Kudsk et al., 2012). Weeds are very high competitors to crop plants due to their analogous nature to growth resources of crop viz., light, moisture, nutrients, space and carbon dioxide which not only diminish the yield, grain quality and impede harvest operations and surges the cost of production. The degree of damage by weeds relies upon the weed type, species density, period and extent of crop weed competition, soil type, soil moisture and soil fertility conditions. So, timely weed management is essential for achieving higher yield. No herbicides are yet standardized to control weeds ingrain amaranth. Weed control is presently done by inter row cultivation but the shortage of labour is a setback. Suitable and economically feasible weed management practices for productive and effective suppression of weeds ingrain amaranth is need of the hour. Therefore, this study was conducted to evaluate the efficacy of different post-emergent herbicides for weed control ingrain amaranth and to assess their effects on crop growth, yield, nutrient uptake, and economics.
Conclusion
Based on the results of this study, it can be concluded that early post emergent application of Quizalofop ethyl 5% EC at 50 g a.i. ha⁻¹ and Propaquizafop 10% EC at 12 g a.i. ha⁻¹ were the most effective herbicide treatments for weed management ingrain amaranth. These herbicides significantly reduced weed density and weed dry weight, resulting in higher nutrient uptake by the crop and ultimately leading to grain yields (1896 and 1805 kg ha⁻¹, respectively) that were statistically comparable to the weed-free check (2162 kg ha⁻¹). The economic analysis revealed that Quizalofop ethyl treatment recorded the highest net returns (Rs. 68,178 ha⁻¹) and B:C ratio (2.56), followed by Propaquizafop (Rs. 63,524 ha⁻¹ and 2.38). Both herbicides showed no phytotoxic effects on the crop. In contrast, the weedy check recorded significantly lower grain yield (1005 kg ha⁻¹), lower net returns (Rs. 25,731 ha⁻¹), and higher weed index (51.29%). Therefore, Quizalofop ethyl 5% EC at 50 g a.i. ha⁻¹ and Propaquizafop 10% EC at 12 g a.i. ha⁻¹ can be recommended as effective post-emergent herbicides for weed management ingrain amaranth, providing farmers with viable options to combat weed competition and improve productivity. CONFLICT OF INTEREST The authors declare no conflict of interest.
