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Fluid Journal : Fluid Journal 1996-1998
Winter 1996 Table 1. Influence of tillage corn response to fertilizer following CRP in east central SD. 1990 Spring 1991 Fertilizer* 1991 Fertilizer* Tillage no yes resp NO3-N** no yes resp bu/A lbs/A-2 ft bu/A MP 122 124 +2 210 156 158 +2 CH 112 126 +14 196 143 161 +18 NT1 82 114 +32 124 120 161 +41 NT2 CRP CRP CRP 58 160 183 +23 * 13-13-13 as a starter in '90 and '91; in 1990, 48 lbs/A N sidedressed on all tillage; in 1991, none on MP and CH, 20 lbs/A N on NT 1 and 40 lbs/A on NT 2. **From fertilized treatments Table 2. Rotation effects on corn yield and N relationships in southwestern Minnesota. * N uptake + tile loss + Fall '94 nitrate - Fall 93" nitrate - fertilizer N. Primary Fall NO3-N Tile Rotation Rotation tillage N yield '93 '94 loss effect* lbs/A bu/A lbs/A-10 ft - ----N, lbs/A----- Cont. corn MP 147 164 150 165 13 -15 Corn soybean none 95 172 118 103 12 +8 Soybean corn MP 0 45 94 99 12 - Corn alfalfa MP 15 170 46 36 3 +73 Corn CRP MP 158 177 41 58 1 -22 lowest following CRP. Calculated rotation effect was similar for CRP and continuous corn, both being negative. Negative numbers indicate that either net immobilization occurred or that N losses exceeded the contribution from organic matter for the season. Prelimi- nary evaluation of this ongoing study indicates that N rates following CRP for similar soil/climate conditions can be based on the preplant nitrate test. Guidelines The following set of guidelines was developed from responses solicited from scientists in different states regarding their views on nutrient management following CRP. Yield goal. Anticipated yield is frequently a factor in determining N needs and is critical in developing an economically sound management plan. It needs to be realistic, taking into account the positive changes that have likely occurred in soil physical properties during the ten years of sod. Soil testing. After a decade of CRP, the status of immobile nutrients such as P, K, or Zn can be determined only with a soil test. Soil test levels will likely be similar to the levels before CRP. How- ever, haying or grazing without fertiliza- tion could cause levels to decline. Liming. If soil tests indicate a need for lime it should be applied before the land is taken out of CRP. For no-till, lime should be applied as soon as possible, using finely ground limestone. Depth of tillage should always be taken into account when lime needs are estimated. Starter. Use of a starter fertilizer containing N, P, and K will provide nutrients early in the season when roots may not be able to obtain adequate nutrition from the soil or decaying residues. P and K. Prior to tillage, a single large P or K application is recom- mended to increase soil test levels to optimum when a single tillage operation is planned for the first year out of CRP followed by no-till. If the CRP land is to be no-tilled and P and/or K soil tests are low or very low, band application is recommended. At higher soil test levels, method of application is less important. Inoculation. Soybeans should be inoculated the first time they are grown following CRP. Nitrogen. Knife applications are often recommended for no-till to reduce immobilization and volatilization. Ongo- ing studies will provide more specific information as it becomes available. Dr. Fixen is North Central director for the Potash and Phosphate Insti- tute, Brookings, SD. !
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