N, P, and K Fertilization for Newly Established Tall Fescue N, P, and K Fertilization for Newly Established Tall Fescue

Summary Second-year production of tall fescue was affected by nitrogen (N) and phosphorus (P) fertilization rates at Site 1 in 2014 and only by N fertilization rates at Site 2 in 2015, with little effect from potassium (K) fertilization at either site.


Introduction
Tall fescue is the major cool-season grass in southeastern Kansas.Perennial grass crops, as with annual row crops, rely on proper fertilization for optimum production; however, meadows and pastures are often under-fertilized and produce low quantities of low-quality forage.This is often true even when new stands are established.The objective of this study was to determine whether N, P, and K fertilization improves yields during the early years of a stand.

Experimental Procedures
The experiment was established on two adjacent sites in fall 2012 (Site 1) and fall 2013 (Site 2) at the Parsons Unit of the Kansas State University Southeast Agricultural Research Center.The soil on both sites was a Parsons silt loam soil with initial soil test values of 5.9 pH, 2.8% organic matter, 4.2 ppm P, 70 ppm K, 3.9 ppm NH 4 -N, and 37.9 ppm NO 3 -N in the top 6 in.at Site 1 and 6.5 pH, 2.2% organic matter, 6.7 ppm P, 58 ppm K, 6.8 ppm NH 4 -N, and 12.3 ppm NO 3 -N in the top 6 in.at Site 2. The experimental design was a split-plot arrangement of a randomized complete block.The six whole plots were combinations of P 2 O 5 and K 2 O fertilizer levels allowing for two separate analyses where 1) four levels of P 2 O 5 consisting of 0, 25, and 50 lb/acre each year and a fourth treatment of 100 lb/acre only applied at the beginning of the study; and 2) a 2 × 2 factorial combination of two levels of P 2 O 5 (0, 50 lb/acre) and two levels of K 2 O (0, 40 lb/a).Subplots were four levels of N fertilization consisting of 0, 50, 100, and 150 lb/acre.P and K fertilizers were broadcast applied in the fall as 0-46-0 (triple superphosphate) and 0-0-60 (potassium chloride).Nitrogen was broadcast applied in late winter as 46-0-0 (urea) solid.Second-year samplings and harvests from each site were as follows.Early growth yield as an estimate of grazing potential in early spring was taken at E2 (jointing) growth stage on April 25, 2014 at Site 1 and on April 29, 2015 at Site 2 from a subarea of each plot not used for later spring and fall harvests.Spring yield was measured at R4 (half bloom) on May 22, 2014 at Site 1 and at R4 (half bloom) on May 19, 2015 at Site 2. Fall harvest was taken on September 24, 2014 at Site 1 and on September 29, 2015 at Site 2.

Results and Discussion
Second-year production of tall fescue (Site 1 in 2014 and Site 2 in 2015) was affected by N and P but not K at Site 1, and predominately only by N at Site 2. At site 1 in 2014, early yield at the E2 (jointing) growth stage to estimate forage available if grazed early, taken in a subarea of each plot not used for later hay harvest, was not affected by P rates (Table 1).At R4 hay harvest in 2014, yields were low at 1.29 ton/acre with no P and approximately 2 ton/acre with P additions of 50 lb P 2 O 5 /acre.Fall harvest yield was unaffected by P rates.Total yield ranged between 2 and 3 ton/acre as affected by P rates averaged across N rates.In contrast, N rate significantly affected all sampling and harvests in 2014 at Site 1. Early growth at E2 (jointing) was increased by each additional increment of N fertilizer, although the response was less at greater N rates.At R4, yield was not increased above the 100 lb N/acre rate.However, fall harvest and the total (R4 plus fall) yield were increased by each increment of N fertilizer.

Table 1 .
Second-year yield of newly established tall fescue in the spring and fall 2014 as affected by P 2 O 5 and N fertilization rates at Site 1

Table 2 .
Second-year yield of newly established tall fescue in the spring and fall 2015 as affected by P 2 O 5 and N fertilization rates at Site 2 lb P 2 O 5 /acre rate was only applied at the beginning of the study (Fall 2013).