Evaluation of Humic Acid Application Methods and Ratios of Nitrogen on Characteristics of Morphological and Yield of Strawberry (Fragaria ananassa Duch.) cv. Paros

Strawberry fruit is soft and has a variety of vitamins, especially vitamin C and minerals. Parus is one of the most important short-day cultivars and suitable for the fresh produce market. Nitrogen is involved in vegetative and reproductive growth of most horticultural crops and excessive use of itdecrease yield and quality of products and increasing pollution of the environment. Humic substances are contained nutrients that improve the soil nutrients and increases the availability of food and therefore plant growth and yield. Studies haveshown that to adding a certain amount ofhumic acid fertilizer with nitrogen can improve the growth of roots, stems and leaves and enhances the yield and quality of products and increases the efficiency of nitrogen fertilizer consumption. On this basis, this research was performed aimed at achieving the best combination of treatments of humic acid and its application method and nitrogen in improving strawberry vegetative and reproductive growth cv. Paros. This study was conducted in the campus of Agriculture and Natural Resources University of Mohaghegh Ardabili at during 2015-2016. In early september, land preparation was carried out, and then were calculated base fertilizers 150 and 50 kg.ha-1 of potassium and phosphorus, respectively plus forty tons per hectare of manure. Stacks was prepared to dimensions of 1.5 × 1 m and the distance of rows was 40 cm. Strawberry seedlings were planted with distance of 25 cm on the row (10plants m-2)in late November.
The experiment was carried out as a split split plot based on complete randomized block design with the application of foliar and soil treatments of Humic acid levels (control, 2, 4 and 6 kg.ha-1) and nitrogen fertilizer (50, 100 and 150 kg.ha-1) with three replications. Nitrogen levels were placed in the main plots and the type of humic acid application in sub plots and humic acid concentrations in the sub- sub plots. Half of N(urea fertilizer) was used at the time of planting and 25 %on the early may and 25 %on the early June. To apply foliar and soil treatments, humic acid was used (Humaster tob with 85% of humic and fulvic acid, Yazd Golsangkavir Company) with the start of the growing season at the intervals of every 10 days once (four times total). In the soil method, humic acid is measured based on the desired treatments and then dissolved with deionized water and added to irrigation water. In the foliar method, after irrigation thehumic acid powder was solutioned with a certain amount of deionized water and it was sprayed on the plants in equal measure. In addition, only irrigation water and deodorizing water were applied to the control of soil and foliar treatments, respectively. Traits were as: leaf number and area, number of runners, fresh and dry weight of shoot and root, root volume, number of flowers and fruits, fruit weight average and yield per plant. Data analysis were performed by using SAS 9.1 and comparison of data by the LSD test at the 5% probability level. All results due to different concentrations of nitrogen, humic acid and methods of its application and their interaction on most traits were significant at 5% probability level. The highest values in the leaf number (17.91) and area (1304.34 cm2) obtained in 6 kg.ha-1 drench application of humic acid. Also,the most number of flowers (13.27) was observed in 100 kgN.ha-1combined with foliar application of humic acid and the highest number of runners (22.34) was obtainedin 150 kgN.ha-1with drench application of humic acid. The most flowers (17.55), fruits (14.5) number and yield (104.43 g.plant-1) observed in 100 kgN.ha-1with 4 kg.ha-1humicacid. The results trilateral interactions of nitrogen,humic acid and application methods showed that the highest values of fresh weight (48.32 g.plant-1) and volume (44.13 cm3.plant-1) of root, dry weight of shoot (21.08 g.plant-1) and root (16.28 g.plant-1) obtained infoliar application of 4 kg.ha-1humic acid.The most of shoot fresh weight (77.7 g.plant-1) also observed in drench application of 4 kg.ha-1humic acid and highestfruit weight average (11.68 g) obtained in foliar application of 2 kg.ha-1humic acid with 100 kgN.ha-1. Results showed that the majority of evaluated traits, the highest values have been achieved of 100 kgN.ha-1with foliar application of 4 kg.ha-1humic acid. On this basis, combined application of chemical and biological fertilizers can be the best strategy to achieve sustainable agriculture and reducing the pollution of soil and water resources along with increasing the product.