A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1225 



has seldom been exceeded in this country. Rate of planting is increased 

 either by closer planting or by increasing the size of the seed piece. 



Harwood and Holden (1893) compiled the results of thirteen experiments 

 conducted at the Michigan station to determine the optimum rate of 

 planting as well as the optimum size of seed piece. The rates of planting 

 varied from 2.7 to 58.9 bushels per acre. The net yields showed that the 

 optimum rates of planting varied from 10.8 to 48 bushels per acre. In 

 only four tests was the best rate of planting higher than 24 bushels. 

 Emerson (1907) tested rates of planting varying from 6 to 36 bushels per 

 acre when eighth, quarter, and half tubers were used. He found that 12, 

 18, and 36 bushels per acre were the best amounts to use for these respective 

 sizes of seed pieces. Macoun (1905), by varying the spacing of the seed 

 from 10 to 18 inches and thereby varying the rate of planting from 35 to 

 19 bushels per acre, obtained the highest net yield from 25 bushels of seed. 

 Kohler (1910), using the varieties Early Ohio and Sir Walter Raleigh, 

 varied the rate of planting in each by 3 and by 2J bushels, respectively, 

 from 6 to 21 bushels in the Early Ohio and from 5 to 20 bushels in the Sir 

 Walter Raleigh. He obtained the highest marketable yield in the Early 

 Ohio from 12 bushels of seed, and in the Sir Walter Raleigh from 17.5 

 bushels. 



Zavitz (1916), using only one-eye pieces, varied the rate of planting 

 from 1.3 to 41.2 bushels by increasing the size of the seed piece. Here 

 both the highest net yield and the highest marketable yield were obtained 

 from using 41.2 bushels of seed. Zavitz's test covered a five-years period, 

 and is therefore more significant in this respect than the other tests just 

 reported. 



The wide variation in the optimum rate of planting shown by the 

 experiments here reported, indicates that the available soil moisture and 

 the fertility have much influence in limiting the stand of plants which 

 will develop to maximum productivity. In other words, the potato soils 

 of Steuben County, which are naturally low in fertility, cannot be expected 

 to produce the average yields that are obtained in Monroe, Franklin, and 

 Clinton Counties. From a review of the data available up to this time, 

 it seems a safe assumption that, under at least average conditions, the rate 

 of planting may be profitably increased from its present average to from 15 

 to 18 bushels per acre. Where weed control is important, labor scarce 

 and expensive, and land relatively cheap, checkrowing is a common 

 system of planting. Tho this system naturally lowers both the rate of 

 planting and the resulting yield, both may be increased by increasing the 

 size of seed piece used. 



Rate of planting on Long Island 



In spite of the fact that the growers on Long Island pay relatively high 

 prices for nearly all of their seed every year, they have apparently learned 



