The effect of manure and chemical nitrogen fertilizers on growth characteristics and tuber yield of potato (Solanum tuberosum L.)

Worldwide interest in potato as a valuable crop for food security is increasing (Camire et al., 2009) and nitrogen (N) nutrition is the main factor determining growth and final yield of potato crops (Bangemann et al., 2014). Nitrogen deficiency limits crop growth, whereas nitrogen excess is often leached into the environment and results in pollution (Hu et al., 2014). Farmyard manure is another source of nitrogen and other nutrients which can decrease the demand for chemical fertilizers. The goal of this study was to investigate effects of using chemical fertilizers and farmyard manure on vegetative growth and tuber yield of potato in order to produce healthy potato crops and efficient utilization of chemical fertilizers and farmyard manure.
A field experiment was conducted in a randomized complete block design with three replications in the Ardabil area in 2013. The experimental treatments included: a control treatment; application of 326 Kg ha-1, 652 kg ha-1 and 978 kg ha-1 of chemical urea fertilizer; application of 21.1 ton ha-1, 42.3 ton ha-1 and 63.5 ton ha-1 of sheep manure; and application of 27.6 ton ha-1, 55.2 ton ha-1 and 82.9 ton ha-1 of cow manure. The fertilizing was done based on the application of 150, 300 and 450 Kg of nitrogen per hectare, respectively. During the growth season, date of emergence, flowering, tuber formation, and at harvesting time, the number of stems per plant, plant height, shoot dry weight and, finally, yield and yield components were measured.
According to the results, yield, yield components and phenological and morphological traits were all significantly influenced by the fertilizer treatments. Increased urea and farmyard manure application delayed full flowering and maturity compared with the unfertilized treatment. The application of cow manure (82.9 ton ha-1) and chemical fertilizer (978 kg ha-1) increased the duration of maturity by about 6.67 and 6.25 percent in comparison to the control, respectively, while emergence was accelerated by increasing farmyard manure. The effect of treatments on the number of stems per plant was significant (P : In general, manures were remarkably superior to chemical fertilizer with respect to growth and yield of potato; the highest yield, weight as well as number of tubers were produced under treatment with 42.3 ton ha-1 and 63.5 ton ha-1 of sheep manure. Hence, this treatment could be considered instead of continuous use of chemical fertilizers as a shift towards sustainable agriculture and to reduce pollution from chemical fertilizers.