Effects Of Seed Piece Size And In-row Spacing On Plant And Yield Traits Of Favorita

Heilongjiang is one of the important potato producers in China. Traditionally, small farmers use ridge of 70 cm or even 65 cm wide, seed piece of 30 g or even less, and in-row spacing of 15-20 cm depending on various varieties for potato production because they lack large agricultural machinery, and use of ridge of 70 cm or 65 cm is convenient for rotation with other crops, such as maize and soybean. In this region, maize and soybean are planted in ridge of 70 cm or 65 cm. In recent years, potato production develops rapidly in the farms of northern Heilongjiang, where land is flat, easy for mechanized operation, and most of farmers use a ridge of 90 cm in potato production. The variety Favorita is favored by both growers and consumers because of its early maturity, high yield, high marketable tuber percentage, and high edible quality. In order to determine suitable seed piece size and in-row spacing for potato variety Favorita cultivated under large ridge(90 cm) in Keshan, Heilongjiang Province, an experiment was carried out to study the influences on plant and yield traits of various seed piece sizes and in-row spacings, relation of yield with plant traits, and interaction between seed piece size and in-row spacing in a two-factor split-plot design of three replications, with seed piece sizes(30 g, 50 g and 70 g) arranged into main-plots and in-row spacings(10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm and 40 cm) into sub-plots, using variety Favorita Elite I as plant materials. The main results are as follows.(1)Effects on stem diameter, main stem number per unit area of various seed piece sizes were highly significant, and plant height and branching stem number per unit area were significant. With increase in seed piece size, planting height had a trend of increase, but no significant difference was detected between 50 g and 70 g seed piece sizes. Also, with increase in seed piece size, stem diameter decreased; number of main stem per unit area increased; and number of branching stem per unit area decreased. There was no significant difference between various seed piece sizes for leaf area index. Effects on plant height, stem diameter, branching stem number per unit area, and leaf area index were highly significant of various in-row spacings, and main stem number per unit area was significant. With decrease of in-row spacing, plant height had a trend of increase; stem diameter and number of branching per unit area deceased; number of main stem per unit area increased, and leaf area index had a trend of increase. For various treatment combinations, there were significant interactions between seed piece size and in- row spacing for plant height and number of main stem.(2)Effects on marketable tuber number and total tuber number, marketable tuber percentage, marketable tuber yield and total tuber yield of various seed piece sizes were highly significant With increase in seed piece size, marketable tuber and total tuber number increased; marketable tuber percentage decreased; marketable tuber(tubers ≥ 75 g) yield increased. However, marketable tuber yield of plants grown from 50 g and 70 g seed piece sizes was not significantly different. Total tuber yield showed the same trend as marketable tuber yield, and the increased rate of total yield sharply decreased with the seed piece size increased. With density increase in in-row spacing from 40 to 10 cm, marketable tuber number had a trend of increase; total tuber number increased; marketable tuber percentage decreased; and total tuber yield increased. When planted at 10 cm apart in the row, the total tuber yield was highest, significantly higher than other spacings, then followed by 15, 20 and 25 cm. There was no significant difference between various in-row spacings for marketable tuber yield. The relationship between marketable yield and in-row spacing was parabola convex functions when planted with seed piece size of 50 g. The optimal seed piece size was 50 g and planting at 20 cm in-row spacing(56400 plants/ha), equivalent amount of seeds 2.78 t/ha, gave the highest marketable tuber yield of16.59 kg/plot(23.05 t/ha), with a marketable tuber percentage(marketable tuber number/total tuber number × 100%) of 59%, and a total yield of20.69 kg/plot(28.75 t/ha) at Keshan in Heilongjiang Province.(3)Correlations of plant height, main stem number per unit area, leaf area index, marketable tuber number and total tuber number to total tuber yield were highly positively significant, while correlations of stem diameter and branching number per unit area to total tuber yield were highly negatively significant. And also correlation of marketable tuber percentage to total tuber yield was negatively significant.(4)Two principal components affecting the yield of various combinations of seed piece size and planting density were selected using principal component analysis. One factor was main stem number- tuber number; the other one was stem height. Therefore, when selecting agronomic traits and yield traits of various combination of seed piece size and in-row spacing large main stem number per unit area and tuber number should be selected while appropriate stem height should be kept.