potato 5-9-12 CLEAN - Vegetableipmasia.org

ORGANIC POTATO PRODUCTION of 6.0, with high P and medium K levels and recommends150 lbs N/acre, 100 lbs P 2 0 5 /acre and 100 lbs K 2 0/acre (seeTable 8.2.2). Because the pH is above 5.5, scab resistantvarieties will be used. The field has 3% organic matter anda stand of red clover that will be turned in a week or soprior to planting (see Table 3.1). Last summer 4000gallons/acre of liquid dairy manure was applied andimmediately incorporated after a hay harvest. Nutrientcredits for soil organic matter, manure, and cover cropappear in Table 8.2.7.Table 8.2.3 indicates about 56 lbs. of Nitrogen will bereleased in the first season from the 4000 gallons of liquiddairy manure. Estimate that each percent organic matterwill release about 20 lbs. of N, so the 3% soil organic matterwill supply 60 lbs. Looking at table 3.1, the red clover willrelease about half its fixed N, or 50 lbs. as it decomposes,for a total estimated N released and available for plantuptake of 166 lbs. per acre. No additional N is needed.The 40 lbs. of phosphate released from the dairy manurewill need to be supplemented with an additional 60 lbsP 2 O 5 This could be achieved by applying 400 lbs per acreof bone meal to meet the soil test recommendation of 100lbs per acre. Potassium will also need to be supplementedin this example. The manure supplies 92 of the 100 lbs.K 2 O needed. Broadcasting 16 lbs. of potassium sulfate froman organically approved product can supply the remaining8 lbs. K 2 O/acre.Table 8.2.7 Example: Calculating Nutrient Credits and Needs Based on Soil Sample Recommendations. Nitrogen (N) lbs/acre Phosphate (P 2 O 5 ) lbs/acre Potash (K 2 O) lbs/acre 1. Total crop nutrient needs: 150 200 200 2. Recommendations based on 150 100 100 soil test 3. Credits a. Soil organic matter 3% 60 0 0 b. Manure liquid dairy, 4000 56 40 92 gallons c. Compost -­‐ none 0 0 0 d. Cover crop – red clover 50 0 0 4. Total credits: 166 40 92 5. Additional needed (2-­‐4) 0 60 8 9. MOISTURE MANAGEMENTWater management and rainfall are among the mostimportant factors determining yield and quality of potatoes.Growth cracks, hollow heart, blackspot, internal necrosis,knobby tubers, seed piece decay, Rhizoctonia and tuberlate blight can be related to excessive amounts of water.Before growing potatoes, consider soil type, rainfalldistribution and the ability to irrigate. Soil types can varythreefold in their respective water holding capacity. Also,note that potatoes have a relatively shallow root system,with an effective rooting depth of approximately 2 feet.Rainfall in the Northeast can provide adequate water for acrop, but it must be distributed evenly over the growingseason to avoid drought stress. During mid-season cropevapotranspiration can easily exceed one inch per week.To prevent drought stress, soils should not be allowed todry below 65 percent of field capacity. On some soil typesrainfall or irrigation would have to occur on a weekly basisto provide the required water for productive crop growth.Rainfall use efficiency can be enhanced by not planting onsteep slopes, properly preparing (tillage) soil to improveinfiltration, and by placing small soil dams in furrows toreduce surface movement. If irrigation is used, watershould be applied to the soil frequently in light amounts tomaintain a uniform and adequate water supply. There areseveral irrigation methods, including center pivot irrigation,solid set sprinklers, wheel line sprinklers, gun and reelunits, furrow irrigation and sub-irrigation. Sprinklerirrigation systems frequently provide the most flexibility andthe best opportunity for efficient water application. Furrowand sub-irrigation require more uniform soil types and arelatively level field, and are more prone to uneven waterapplication.10. HARVESTING10.1 Vine KillingPotatoes need 2-3 weeks between vine kill and harvest topromote tuber maturity and adequate skin set. Mature skinprotects tubers from disease, resists skinning and bruisingduring harvest and transport, and prolongs tuber storagelife.Optimally, vine killing is accomplished mechanically usinga flail mower. A flame weeder might be used several daysafter mowing to assure complete vine kill. Care should betaken to minimize damage to tubers by mowing equipmentor by dislodged rocks that can also injure tubers.Vines can also be allowed to senesce naturally by reducingwater applications in some cultivars. Another option is toallow frost to kill the vines. However, potatoes left tomature in the ground for 2-3 weeks after a frost aresusceptible to damage by additional frosts and disease.Currently none of the herbicides approved for certifiedorganic farmers are labeled for vine kill. Research isneeded to determine the effects of potential organicallyapproved vine-kill products on tuber quality.10.2 Early Maturity and Timely Harvest.Use of early maturing varieties and scheduling vinekilling/harvest as soon as the crop is mature eliminates thefood source for the Colorado potato beetle and reduces thenumber and health of overwintering adults. This practice isalso useful in minimizing crop damage by late-season pests,especially aphids and the virus pathogens they transmit.See updated Cornell HUpostharvest storage notesUH (Reference 45)202012