Effect of Sowing Window and Phosphorus Levels on Growth and Yield of Summer Fodder Cowpea

Green forages, the foremost component in the livestock production, have cooling effect on the animal body as they are palatable, easily digestible, nutritious and slightly laxative. The use of concentrates provides highest animal production per unit feed intake, but this may not be economical in countries like India where grains and concentrates are costly and/or having limited supply. Though cereal-based green fodders are palatable, succulent and nutritious with sufficient amount of carbohydrates, they are deficient in protein which is necessary for animal health and productivity. Proteins can be supplemented through leguminous green fodders. Cowpea [Vigna unguiculata (L.) Walp.] has emerged as a potential crop for meeting the requirements of high quality fodder to the fast expanding cattle populations. It is a major source of plant proteins and vitamins for man, feed for animals and also a cash crop. It provides palatable, notorious and balanced feed to milch animals. It contains 20-24% crude protein, 23-25 per cent cellulose and 5-6 per cent hemicelluloses on dry matter basis. The fodder cowpea has digestibility of about 70 per cent. Cowpea, when fully nodulated, can fix 20 to 140 kg N ha^-1 in the soil. There is a wide gap between the demand and supply of green forage particularly during the lean period, which can be reduced through the agronomic approaches. Among these, sowing window and fertilizer application are considered to be the most important factors affecting the production potential of the crop. The sowing time of the fodder cowpea affects the fodder supply to considerable extent and hence, proper sequence of sowing the crops should be adopted in order to achieve maximum fodder yield along with maintaining the regular supply of the green fodder. Among the nutrients, phosphorus has an adverse impact on legume production as it is one of the vital nutrients required for optimum growth, development, productivity of plants (Kumar et al., 2021), as well as for nodulation and enhanced N-fixation (Yadav et al., 2017). Being the leguminous crop cowpea responds more to phosphoric nutrient than nitrogen and potassium. Considering the above facts, the present investigation was taken up in order to find out the optimum time of sowing and optimum dose of phosphatic fertilizer for the production of fodder cowpea.

The field experiment was conducted at S.V. Agricultural College Farm, Tirupati campus, Acharya N. G. Ranga Agricultural University during the summer, 2019. The soil of the experimental field is sandy loam in texture, neutral in reaction, low in organic carbon and available nitrogen, medium in available phosphorus and potassium. The experiment was laid out in split-plot design with three sowing time viz., I FN of January, II FN of January and I FN of February assigned to main plots and four levels of phosphorus viz., 0, 20, 40 and 60 kg P₂O₅ ha^-1 allotted to subplots. The weekly weather data prevailed during the season is given in Fig 1. Phosphorus was applied as per the treatments while nitrogen was applied in common to all the treatments.
 

Growth parameters
 
The results indicated that all the growth parameters (plant height, number of leaves plant^-1, number of branches plant^-1, dry-matter production and number of nodules plant^-1) were higher for the crop sown during I FN of January followed by that sown during II FN of January (Table 1) with no significant disparity between them. This might be due to the favourable climatic conditions that prevailed during the crop growth period and might have been instrumental in boosting up the crop growth. Our findings are in agreement with the findings of Kumar and Patel (2013) and Ahmed et al., (2017). A lower stature of growth parameters was recorded for the crop sown during I FN of February.
       
Application of 60 kg P₂O₅ ha^-1 resulted in significant improvement in the growth parameters at all the stages of observation while the lowest value was recorded under the control (Table 1). Increase in the growth parameters with increasing phosphorus level can be attributed to the fact that phosphorus is required in large quantities in shoot and root tips where metabolism is high resulting in favourable effect on cell division/enlargement that is reflected on growth of the plant. Similar findings were observed with Kumar (2011) and Shekara et al., (2010). The interaction between time of sowing and phosphorus level influencing the growth parameters was observed to be non-significant.
 

 
Leaf to stem ratio and fodder yield
 
Higher leaf to stem ratio and green fodder yield of fodder cowpea was recorded when the crop was sown during I FN of January which was however on par with that of II FN of January (Table 2). The higher leaf to stem ratio and fodder output with earlier sowings could be related to higher leaf weight than green stem weight, as well as the fact that early seeded crops took the most calendar days to harvest, resulting in a longer vegetative period, which in turn reflected on the green fodder production. The results are in consonance with the findings of Ashwathi (2016), Ali et al., (2007) and Ram et al., (2014). Fodder cowpea sown during I FN of February recorded the lowest leaf to stem ratio and fodder yield (Table 2).
 

               
The highest phosphorus level of 60 kg P₂O₅ ha^-1 resulted in significantly higher leaf to stem ratio and green fodder yield compared to the lower levels of phosphorus tested. The next best treatment was 40 kg P₂O₅ ha^-1 which was however on par with that of 20 kg P₂O₅ ha^-1 (Table 2). The lowest leaf to stem ratio and green fodder yield was recorded with control (Table 2). The higher leaf to stem ratio and green fodder yield may be due to adequate nutrient supply and efficient utilisation through an extensive root system developed by phosphorus application, which resulted in higher plant height, leaf area, number of leaves plant^-1 and number of branches plant^-1. These results are in line with the earlier findings as reported by Shekara et al., (2012), Godara et al., (2016) and Kumawat and Khinchi (2017).

A larger part of the areas under cultivation is deficient in one or other nutrients. Therefore, the need of the day is to manage nutrient deficiencies to maximize the crop yield and quality (Kumar et al., 2022). The present investigation indicates that fodder cowpea gives optimum growth and yield on sown during I FN of January with basal application of P₂O₅ at the rate of 60 kg ha^-1. If sowing is delayed due to any of the reasons, it can be postponed until II Fortnight of January without a significant reduction in yield. This help managing both nitrogen and phosphorus nutritional requirements.

None.