During the past several years considerable experimenting has been aimed at developing methods for improving potato yields. One of the easiest and most effective ways found was to adjust the seed piece size and number of eyes per piece. Seed pieces were cut to meet the following size categories: 1/2, 1, 1-1/2, and 2 ounces and small whole tubers; 1-1/2, 2 and 2-3 ounces. Significant differences in yield were obtained between the various seed piece size treatments. The yield advantage was in favor of the larger size. The number of eyes per piece was less important except with the smallest size. In this case the seed pieces were incapable of adequately supplying plant growth from more than one eye. Small, whole tubers from good high yielding fields were found to be excellent for seed potato pieces.

The importance of proper fertilizer placement has been demonstrated in recent greenhouse studies. Small, seemingly unimportant changes in fertilizer placement often in reality are very important. Specially constructed boxes with glass fronts were used to study root development as affected by fertilizer placement. Yields were significantly different one from another with the poorer ones resulting where fertilizers were placed too close to the seed piece. Yields ranging from 298 cwt, where the fertilizer was placed two inches to each side and level with the seed piece; up to 367 cwt where the fertilizer was placed four inches to each side and two inches below the seed piece. Root burning and speed of root regeneration represent the most important consideration to be reckoned within the proper placement of fertilizer.

Data from five years of experimentation with irrigation and soil moisture levels indicate that a certain knowledge and general understanding of these factors is important in potato production. Nine treatments ranging from a constant very wet level to a constant dry treatment were used. Yield differences were significant and varied from a low of 321 cwt, from plants exposed to a very wet (18-20 centibars tension) level early in the season followed by a dry (75-80 centibars tension) condition during the last part of the growing season, to 416 cwt where the plants were kept at a dry level early and changed to a very wet level late in the season. Growers often unknowingly reduce yields and lower quality by applying excessive amounts of irrigation water.

No description available.

Ten percent granular formulations of phorate and Di-Syston at 20 pounds per acre will effectively control psyllids, aphids and thrips on potatoes. Two years study varying the placement of granular systemic insecticides in the soil in relation to the seed piece has not produced any significant differences in the insect control. The yields from plots in which the granules were placed four inches to the side and two inches below the seed piece were greater. All were better than the untreated check. Of two new systemic insecticides applied as granules at planting time, the material US-21149 (Temik R) gave outstanding insect control and above average yields on Kennebec variety potatoes. Compound NIA-10242 gave less effective insect control and yields below UC-21149.

Isolates of Verticillium Albo-atrum were obtained from potato and from cotton. Investigations are in process to ascertain the relationship between cotton Verticillium wilt and potato Verticillium wilt and to determine the significance of the disease to Arizona potato production.

Investigations on the problem of black-leg and tuber rots have revealed an interaction between two pathogenic organisms, a bacterial species and Pythium aphanidermatum.

No description available.

In potato variety trials in Central Arizona, Kennebec and Merrimack performed the best as potatoes for chipping. Red varieties Viking, LaRouge, and Red LaSoda yielded about the same as Red Pontiac, the standard for the area; however, Viking had much better appearance and uniformity than the other three reds.

In a fertilizer study in the Queen Creek area, a strong response to nitrogen and phosphorus fertilizers was obtained. Potatoes did not respond to potassium when applied with nitrogen and phosphorus.