TITLE:

Nitrogen, Phosphorus, and Zinc Management for Irrigated Peanut at AG-CARES, Lamesa, Texas, 2000 and 2001.

AUTHORS:

                K.F. Bronson, C. L. Trostle, M. Schubert, J.L. Mabry, J.D. Booker, Assistant

Professor, Extension Specialist, Associate Professor, Technician, and Research

Associate.

METHODS AND PROCEDURES:

                Experimental Design:         Randomized complete block with 5 replications

                Plot size:                       40 ft ( 12 40-inch rows) X 50 ft

                Soil type:                             Amarillo fine sandy loam

                Variety:                                Flavor Runner 458

                Planting date:                     Early May

                Harvest date:                     Early November

                Irrigation:                            LEPA on a 3.5 day schedule at 75% estimated cotton ET replacement

SUMMARY

IN 1999, THE FIRST YEAR OF THIS STUDY, HIGH YIELDS OF > 6,000 LB/AC WERE OBTAINED, WITH NO N, P, OR ZN FERTILIZER BENEFIT. IN PRODUCTIVE YEARS AND POOR-YIELDING YEARS ALIKE, THIS STUDY HAS INDICATED THAT FERTILIZER RESPONSES IN PEANUT AT AG-CARES ARE DIFFICULT TO DOCUMENT.

RESULTS AND DISCUSSION:

Soil test values (0-6 in.) measured before planting in 2000 for NO₃-N, Mehlich 3-P, and Zn were 8 ppm, 17 ppm and 0.33 ppm, respectively. Peanut plants were dwarfed and chlorotic in 2000, most likely due to StrongArm® herbicide injury. An average response to N fertilizer of 300 lb/ac was observed in 2000 (Table 1). No effects of P, Zn, or interactions between N, P, or Zn were observed on peanut yield. The N fertilizer response to peanut observed in 2000 has only been seen once in the last five years. It was probably related to the herbicide injury. Leaves at mid-season in the plus N plots averaged 3.04 % N and 20.0 ppm Zn compared to 2.75 % N and 18.6 ppm Zn in the minus N plots (significantly different at 0.05 probability level). These N tissue levels were below published critical values, further indicating negative influence of the herbicide StrongArm®. Spectral reflectance at 0.5 m above the mid-season canopy was not related to final peanut yields. However, green vegetative indices were positively affected by N fertilizer, indicating that aboveground biomass was enhanced with N additions.

Spring 2001 soil test values were 5.6, 21.9, and 0.71 ppm NO₃-N, Mehlich 3-P, and Zn, respectively. Peanut yields were low again this year, (average of 2600 lb/ac) possibly due to poor fruit set in the hot dry conditions with LEPA irrigation. Several spray irrigations were applied to alleviate this condition. There was no effect of N, P, Zn or interactions of these on peanut yield (Table 1). Mid-season leaf N was 4.00 % in plus N plots vs. 3.81 % in minus N plots (significantly different at 0.05 probability level). Leaf P was 0.253 % P in plus Zn plots vs. 0.246 % in minus Zn plots (significantly different at 0.05 probability level). The mid-season analyses of leaves indicates that although peanut yields were not affected in either year, fertilizer additions did positively affect leaf nutrient status. Green and red vegetative indices of mid-season peanut canopy were positively related to final peanut yield and negatively related to leaf Zn. Red vegetative indices were positively affected by Zn fertilizer additions.

Drawing conclusions from this fertilizer study after three years is not easy. Unusual conditions were present in 2000 and 2001, resulting in low yields.

Table 1. Peanut yields as affected by nitrogen, phosphorus, and

zinc fertilizer, AG-CARES, Lamesa, Dawson County,

Amarillo fine sandy loam, 2000 and 2001

^a 30 lb P₂O₅/ac in 2001