How does the planting density of open-field potatoes affect yield?

Potatoes in Tongren City are mainly grown as an early-maturing vegetable. In order to explore the optimal density for open-field cultivation of virus-free potatoes, the Tongren City Agricultural Technology Station conducted a density trial on open-field cultivation of virus-free potatoes from 2006 to 2007.

1 Materials and Methods

1.1 Overview of the trial site The trial site was selected in the contracted field of Yang Xiuming, Hongdong Group, Mulong Village, Bahuang Town, Tongren City, at an altitude of 260 m. The trial field had sandy loam soil with medium fertility, and the previous crop was Houttuynia cordata (fish mint).

1.2 Trial materials The test variety was first-grade seed potatoes of "virus-free Mira", provided by Weining Ruifeng Agriculture and Animal Husbandry Co., Ltd. of Guizhou Province.

1.3 Trial design Five treatments were set up: Treatment 1 (CK), the conventional local planting density of 120,000 hills/hm2; Treatment 2: 135,000 hills/hm2; Treatment 3: 150,000 hills/hm2; Treatment 4: 165,000 hills/hm2; Treatment 5: 180,000 hills/hm2. A randomized block design was used with 3 replications. The plot area was 16.82 sq m (9.33 m long, 1.8 m wide). A 40 cm path was left between replications and between treatments, and border rows were set up around the perimeter.

1.4 Field management Sowing was carried out on December 18, 2006, and at sowing 30,000

kg/hm2 of clear manure water and 375 kg/hm2 of single superphosphate were applied; on March 16, 2007, 450 kg/hm2 of phosphate fertilizer was applied; harvest was on April 29, 2007. At harvest, 10 hills were randomly sampled from each plot for investigation, and then each plot was harvested separately for yield measurement.

2 Results and Analysis

2.1 Effect of different densities on yield As can be seen from Table 1, Treatment 5 had the highest yield, with an average yield of 21919.65 kg/hm2, an increase of 24.69% over the control; Treatment 4 was next, with a yield of 21265.63 kg/hm2, an increase of 20.97% over the control; Treatment 3 was third, with a yield of 20195.42 kg/hm2, an increase of 14.88% over the control; Treatment 2 had a yield of 18688.81 kg/hm2, and the control had a yield of 17579.36 kg/hm2. Analysis of variance showed that the differences among treatments reached the 0.01 significance level, while the differences among replications were not significant. Treatment 5 showed significant differences from Treatments 3, 2, and 1 (CK), while Treatment 5 showed no significant difference from Treatment 4. In areas at an altitude of about 260 m under open-field cultivation, a density of 165,000-180,000 hills/hm2 gave relatively high yields.

2.2 Effect of different densities on growth period Under different cultivation densities, the growth period of each treatment was the same, with the number of days from emergence to harvest all being 131 d. The growth progression was the same, and density had no effect on the growth period of open-field cultivated virus-free potatoes.

2.3 Effect of different densities on economic traits As can be seen from Table 2, the plant height of potatoes under different treatments ranged from 57.0 to 70.2 cm, with Treatment 5 having the tallest plants and CK the shortest; stem thickness ranged from 0.84 to 1.03 cm, with Treatment 5 having the thinnest stems and CK the thickest stems; the number of branches ranged from 1.80 to 2.67, with Treatment 2 having the most branches and Treatment 5 the fewest; the average tuber weight per plant was highest in CK and lowest in Treatment 5. As density increased, plant height increased, stem thickness decreased, and the number of branches decreased. The highest number of tubers per plant was in CK. The most large tubers (over 70 g) were in CK; the most medium tubers (50-70 g) were in CK and Treatment 2; the most small tubers (under 50 g) were in Treatments 3 and 4.

3 Summary

In summary, choosing a suitable planting density and giving full play to the combined advantages of individual plants and the population is a key technical measure for obtaining high yields in open-field potato cultivation. The trial results showed that in areas at an altitude of about 260 m, the optimal density range for open-field cultivation using virus-free potatoes is 165,000-180,000 hills/hm2.