Himachal Journal of Agricultural Research Vol. 29 (1 & 2) : 11-15, 2003
Response of grain amaranth (Amaranthus hypochondriacus L.) to phosphorus and potassium under irrigated conditions
S.S. Rana and Rameshwar*
CSK HPKV, Mountain Agricultural Research and Extension Centre
Sangla, Kinnaur 172106 HP
Abstract
An experiment was conducted on grain amaranth during the summer seasons of 2000 and 2001, to find out optimum phosphorus and potassium dose. Plant height, inflorescence length, rachis per inflorescence and yield increased significantly with the increasing rates of P2O5 upto 40 kg/ha. Yield and yield attributes decreased significantly at 60 kg P2O5/ha over 40 kg P2O5/ha. Similarly, amaranth responded to K2O application upto 40 kg/ha. Maximum grain yield (2414.8 kg/ha), net returns (Rs. 29091/ha) and B: C ratio (Rs. 1.73) could be obtained with 40 kg each of P2O5 and K2O/ha. The optimum dose for P2O5 and K2O was 42.8 and 39.7 kg/ha, respectively.
Introduction
Amaranth as an alternative crop shows significant promise all over the world. It is an important crop in India and the adjoining countries such as Nepal and Pakistan where it is grown in hills as well as in plains. In North Indian hills, the crop is usually planted in un-irrigated marginal land generally without chemical fertilizers at the break of the monsoon. However, crop is responsive to irrigation (Mishra et al, 1997) and nutrients (Tewari and Mishra, 1997, Bhaskar et al, 1996, Elbehri 1993, Panchal et al, 1991, and Subham 1989).
Though nitrogen has been amply studied, a little work has been done for phosphorus and potassium. Keeping the fact in mind, the present investigation was undertaken to study the response of phosphorus and potassium in the irrigated grain amaranth.
Materials and Methods
The field experiment was conducted on sandy loam soils (pH, 6.7) during the summer seasons of 2000 and 2001 at Sangla (2590.8 m above msl, 31° 25' 56'' N latitude and 78° 15' 3'' E longitude) under irrigated conditions in factorial randomized block design with three replications. The soil contained 0.60% organic carbon, 16.7 kg available phosphorus, 161 kg available K and 210 kg available N/ha. The rainfall received during the crop growing seasons of 2000 and 2001 was 159 mm and 213 mm, respectively. The treatments were comprised of combinations of three levels (20, 40 and 60 kg/ha) each of P2O5 and K2O plus one absolute control. FYM @ 10 tonnes/ha was applied uniformly at the time of field preparation. The cultivar Annapurna was sown on May 29, 2000 and May 31, 2001 after pre-sowing irrigation at a row to row
spacing of 50 cm using 7.5 kg seed/ha. The fertilizer nutrient N @ 80 kg/ha was applied in three equal splits viz. at sowing, gap filling and thinning and panicle/inflorescence initiation stages. The required quantity of P2O5 and K2O as per the treatment was applied as basal along with first dose of N. When the seedlings were about 10-15 cm in height, the crop was resorted to thinning and gap filling after irrigating the field to obtain the desired stand keeping intra-row spacing of approximately 10 cm. Subsequently three irrigations were given at 20-25 days interval. Weeds were controlled manually thrice at thinning and gap filling, panicle initiation and panicle enlargement stages.
Growth and yield contributing traits were recorded at harvest. Grain yield was harvested from net plot. Economics of the treatment was computed based upon the prevalent market prices.
Results and Discussion
Effect of phosphorus
Application of 40 kg P2O5/ha significantly increased grain yield of amaranth by 8.96% over 20 kg P2O5/ha (Table 1). This was mainly due to significant increase in growth and yield contributing characters. Tewari and Mishra (1997) reported similar effects of P2O5 on amaranth grain yield. Elbehri et al (1993) obtained linear response to the applied P when initial soil test indicating low nutrient status. Plant height, inflorescence length, rachis per inflorescence and grain yield decreased significantly due to 60 kg P2O5/ha over 40 P2O5/ha during the second year of investigation which may be due to the combined effect of direct and residual P. The decrease in yield at higher level may be due to operation of law of diminishing returns because at lower level of nutrient applied there is more competition among the plants for applied nutrients (Tisdale et al., 1990). The relationship of seed yield and applied P2O5 was also studied with the help of regression equation as below,
Y = 1547 + 26.5775 P-0.2966 P2
At optimum dose (42.86 kg/ha), the response was 594.2 kg/ha of grains. The response per kg P2O5 applied was worked out to be 13.86 kg of grain.
Effect of potassium
Response of potassium was also significant on growth, yield attributes and yield of grain amaranth (Table 1). Plant height, inflorescence length, rachis per inflorescence and grain yield increased significantly due to the application of 40 kg K2O/ha over 20 kg K2O/ha. The yield contributing characters and yield decreased significantly due to 60 kg K2O/ha over 40 kg K2O/ha during both the years of investigation. Based upon mean grain yield the following response model was predicted for potassium,
Y = 1219.7 + 50.09 K - 0.2966 K2
Response of 1003.94 kg/ha was obtained at optimum dose of 39.77 kg K2O/ha. The response per kg K2O applied was 25.24 kg of grain.
On an average P and K application increased grain yield of amaranth by 27.55% over absolute control by influencing growth and yield contributing characters favourable.
Interaction
P and K levels interacted significantly in influencing grain yield of amaranth (Table 2). At 20 kg K2O/ha, mean grain yield increased significantly upto 40 kg P2O5/ha beyond which no significant yield increase was recorded. At 40 kg K2O/ha level, there was drastic reduction in grain yield due to 60 kg P2O5/ha over 40 kg P2O5/ha. Whereas at the highest level of K2O, amaranth grain yield remained statistically unaltered due to P2O5 levels tried. Similarly at 20 or 40 kg P2O5 levels response of K2O was upto 40 kg/ha. 40 kg/ha each of P2O5 and K2O was found to be the best nutrient
Table 1. Effect of phosphorus and potassium on growth, yield contributing traits and yield of grain amaranth
Treatment / Plant height(cm) / Inflorescence
length (cm) / Rachis/
inflorescence / Yield/plant (g) / Grain yield
(kg/ha)
2000 / 2001 / 2000 / 2001 / 2000 / 2001 / 2000 / 2001 / 2000 / 2001 / Mean
P levels
20 / 136.9 / 158.1 / 41.8 / 53.7 / 18.1 / 38.1 / 6.60 / 7.03 / 1808 / 2113 / 1961
40 / 140.8 / 160.9 / 44.6 / 55.2 / 20.2 / 41.4 / 7.27 / 7.55 / 2002 / 2270 / 2136
60 / 142.5 / 151.5 / 45.6 / 48.2 / 22.4 / 35.6 / 7.72 / 6.57 / 2137 / 2013 / 2075
LSD (P=0.05) / 2.7 / 1.4 / 1.1 / 1.3 / 1.2 / 1.2 / 0.33 / 0.32 / 100 / 141 / 116
K levels
20 / 140.6 / 154.8 / 44.1 / 51.9 / 20.0 / 37.6 / 7.26 / 7.05 / 1956 / 1987 / 1972
40 / 142.3 / 159.3 / 45.8 / 54.7 / 22.1 / 40.6 / 7.73 / 7.86 / 2121 / 2326 / 2224
60 / 137.4 / 156.3 / 42.2 / 50.6 / 18.7 / 36.9 / 6.58 / 6.24 / 1869 / 2080 / 1976
LSD (P=0.05) / 2.7 / 1.4 / 1.1 / 1.3 / 1.2 / 1.2 / 0.33 / 0.32 / 100.0 / 141 / 116
Control v/s others
Control / 130.5 / 148.1 / 38.6 / 45.7 / 14.2 / 32.4 / 5.81 / 5.67 / 1492 / 1733 / 1613
Others / 140.1 / 156.8 / 44.0 / 52.4 / 20.3 / 38.4 / 7.19 / 7.05 / 1982 / 2132 / 2057
LSD (P=0.05) / 3.4 / 1.8 / 1.5 / 1.7 / 1.6 / 1.6 / 0.43 / 0.41 / 143 / 182 / 150
Table 2. Integrated effects of P and K on grain yield and economics
K levels / Grain yield (kg/ha) / Net returns (Rs./ha) / B:C ratio (Rs)P levels / P levels / P levels
20 / 40 / 60 / 20 / 40 / 60 / 20 / 40 / 60
2000
20 / 1613.3 / 1914.3 / 2340.7 / 14449 / 19729 / 27391 / 0.89 / 1.19 / 1.60
40 / 1975.7 / 2174.3 / 2214.3 / 21186 / 24521 / 24842 / 1.30 / 1.46 / 1.44
60 / 1835.7 / 1917.7 / 1852.7 / 18378 / 19498 / 17824 / 1.11 / 1.15 / 1.03
LSD (P=0.05) / 191.0 / 3645 / 0.16
2001
20 / 1944.3 / 2111.1 / 1905.7 / 20738 / 23468 / 19126 / 1.28 / 1.42 / 1.12
40 / 2211.3 / 2655.3 / 2111.3 / 25663 / 33660 / 22885 / 1.57 / 2.00 / 1.33
60 / 2183.0 / 2044.7 / 2022.3 / 24977 / 21911 / 21047 / 1.51 / 1.29 / 1.21
LSD (P=0.05) / 244.0 / 4650 / 0.16
Mean
20 / 1778.8 / 2012.7 / 2123.2 / 17594 / 21599 / 23259 / 1.09 / 1.31 / 1.36
40 / 2093.5 / 2414.8 / 2162.8 / 23425 / 29091 / 23864 / 1.44 / 1.73 / 1.39
60 / 2009.4 / 1981.2 / 1937.5 / 21678 / 20705 / 19436 / 1.31 / 1.22 / 1.12
LSD (P=0.05) / 201.4 / 3880 / 0.11
combination in increasing grain yield significantly over rest of the nutrient combinations. The net returns and B: C ratio assumed almost similar trend as to that of grain yield. The combination of 40 kg/ha each of P2O5 and K2O resulted in maximum
net returns (Rs. 29091) and B: C ratio (Rs. 1.73). Results from this study suggested an application of 42 kg P2O5/ha and 39 kg K2O/ha for optimum productivity of grain amaranth under irrigated conditions
.
References
Bhaskar, J., Bhard, J.M. and Patil, S.N. 1996. Effect of plant population, nitrogen, and phosphorus on grain amaranth (Amaranthus spp.) Indian Journal of Agronomy 41(1): 181-182.
Elbehri, A., Putnam, D.H. and Schmitt, M. 1993. Nitrogen fertilizer and cultivar effects of yield and nitrogen use efficiency on grain amaranth. Agronomy Journal 85(1): 120-128.
Mishra, P.N., Tewari, S.K. and Singh, D. 1997. Scheduling of irrigation in grain amaranth (Amaranthus hypochondriacus L.) grown on marginal soils. Annals of Agricultural Research 18(3): 304-308.
Panchal, D.B., Patel, R.B. and Dalaa, K.C. 1991. Effect of nitrogen and phosphorus on grain yield and nutrient uptake by grain amaranth. Gujrat Agricultural University Research Journal 16(2): 71-72.
Subhan 1989. Effect of dosage and application time of nitrogen fertilizer on growth and yield of amaranth (Amaranth tricolor L). Buletin Penelitian Hortikultura 17(3): 31-40.
Tewari, S. K. and Mishra, P.N. 1997. Response of grain amaranth to nitrogen and phosphorus in sodic soils of UP. Annals of Agricultural Research 18(4): 533-535.
Tisdale, S.C., Nelson, W.C. and Beaton, J.B. 1990. Soil fertility and fertilizers. MacMillan Publishing Inc. New York