Effect of nitrogen,phosphorus, and potassium fertilizers on yield components and specific gravity of potatoes

Netted Gem potatoes were grown at four levels of N, three of P, and two of K fertilizer in metal lysimeters protected from rain by an automatic shelter. The first two increments of N fertilizer, 200 and 400lb/acre (224 and 448 kg/ha), successively increased yields by increasing the number of tubers produced. The first increment also increased the average tuber weight. With 800 lb N/acre (896 kg N/ha), tuber yield and grade of potatoes were reduced from those of the 400-lb/acre (448-kg/ha) treatment becuase the average weight per tuber was reduced. P fertilizer increased yield by increasing the average tuber weight. The increased yield due to N and P fertilizers was almost entirely in the form of Canada No. 1 potatoes. K fertilizer did not affect number or weight of tubers in this high-K soil.     

Effect of chemicals on vine kill,yield and quality of potatoes in the Red River Valley

Sodium arsenite at 9 lb, DNBP at 2.5 lb, diquat at 1 lb, paraquat at 0.5 and 1 lb and prep at 2 and 4 lb/acre were tested as vine killers for potatoes during 1963, 1964 and 1965. Based on ratings 1 or 2 days after spraying, 1 lb diquat, 1 lb paraquat and 2.5 lb/acre DNBP resulted in the quickest kill. Paraquat at 0.5 lb and sodium arsenite at 9 lb/acre were slightly slower. Prep at 2 and 4 lb/acre was consistently slowest. Some of the slower acting chemical gave equally good kill after 7 days. Chemical vine killing usually reduced yields and specific gravity by shortening the growing period. There was no effect from any of the chemicals on the color of potato chips. A slight amount of vascular discoloration did occur in tubers from all treatments. Vascular discoloration of tubers from vines treated with prep at 2 lb/acre was greater than that of tubers from vines which were cut and not sprayed. None of the vascular discoloration was severe enough to be economically important. In a second test sodium arsenite at 9 lb and diquat at 0.5, 1 and 2 lb/acre were applied as single and split applications in 1963. The major effect from the split applications was a slower rate of vine kill.     

Effect of simulated hail damage on yield and quality of Russet Burbank potatoes

The yield and quality response of Russet Burbank potatoes to simulated hail damage was dependent upon the amount of damage and on the growth stage at which the damage occurred. Plots of Russet Burbank potato plants were subjected to 0%, 10%, 25%, 50%, 75%, or 100% defoliation at 3, 5, 7, 9, 11, or 14 weeks after emergence. A motorized flail was used to simulate the complex damage that occurs during a natural hail storm. Early season simulated hail damage, when the plants were mainly vegetative, caused yield losses proportional to the degree of damage. Simulated hail damage during the early phases of tuber growth caused minor yield losses (< 5%) at low defoliation levels but severe losses at the higher levels with proportional loss of tuber quality. Defoliation later in the season resulted in progressively less reduction of both yield and quality. At or near maturity, late season simulated hail damage caused insignificant losses unless the stems were damaged enough to prevent nutrition and carbohydrate translocation into the tubers.     

Effects of harvesting method and date on yield loss and seed quality of rapeseed

China is one of the major rapeseed production countries in the world,but harvesting mechanization was still backward,and high harvest loss was a key inhibiting factor for rapeseed production.To obtain optimum harvesting date for winter rape in the Yangtze River Valley of China,artificial simulated combine harvesting and artificial two-stage harvesting were adopted to find correlations between harvesting date,rape variety,seed oil content,protein content,grain moisture rate,rapeseed straw moisture content,rapeseed unthreshing rate,grain drop loss rate,thousand seeds weight(TSW),and harvesting economic coefficient(HEC).Analysis of variance showed that rapeseed oil content,protein content and TSW were correlated with rape variety;HEC was correlated with harvesting method and rape variety.Rape variety was the dominant factor of rapeseed oil content,protein content,TSW and HEC.Grain moisture rate,un-threshing rate,grain drop loss rate and straw moisture content were correlated with harvesting method and date.Harvesting date was the dominant factor of rapeseed moisture rate,un-threshing rate,grain drop loss rate and straw moisture rate.Single factor tests further proved that harvesting date had less impact on rapeseed oil content,protein content,TSW and HEC.It showed little correlation with rapeseed quality except grain moisture rate.The optimum harvesting date could be known by change in straw moisture content.The combined harvesting should be carried out during the grain moisture content of 15%-20%with TSW stabilized in the highest level.The twostage harvesting cutting should be carried out at the grain moisture content of 35%-40%.This research offered a reference to harvesting method and date for rape cultivated in the Yangtze River Valley.     

Relations between specific gravity,dry matter content and starch content of potatoes

Summary Published relations between specific gravity, dry matter content and starch content are summarized in the form of regression equations and a diagram. It is suggested that, for the potato literature, uniformity of presentation of results and of conversion equations used would be desirable.