Late Nitrogen to Increase Protein of Sceptre Durum

Introduction

Durum wheat has been the cereal of choice for many producers in Saskatchewan. It has greater disease tolerance than many classes of wheat, and produces higher yields under irrigation than does hard red wheat. The short strawed variety Sceptre is preferred by irrigators for its high yield potential and lower susceptibility to lodging. Sceptre commonly produces a lower grade and quality of grain with an inferior protein content.

Applying nitrogen after the boot stage increases grain protein and reduces piebald kernels in durum wheat. Research has indicated an increase in protein content with increased quantity of applied nitrogen.

A project was conducted by T.J. Hogg, of SIDC, to determine the effect of late nitrogen applications on the protein content of irrigated Sceptre durum in order to improve returns to producers.

• Application of nitrogen at flowering can increase the grain protein content of Sceptre durum
• Fertilizing to soil test recommendations prior to seeding provides sufficient nitrogen to produce high yields and protein with the least risk

Methods

Two sites in 1995 and one site in 1996 were sown to Sceptre durum using a plot drill with Conserva-Pak openers on 30 cm spacing.

Soil samples were taken prior to seeding. Soil test recommendations were 120 to 130 kg/ha nitrogen for all sites. Pre-plant nitrogen was applied at 0, 30, 60, 90, and 120 kg/ha actual nitrogen as 34-0-0. Phosphate fertilizer was side-banded at 30 kg P₂O₅/ha. Late nitrogen treatments were applied to the crop at flowering at rates of 20, 40, and 60 kg N/ha.

A second trial compared nitrogen sources for their effect on protein. Pre-plant nitrogen was applied at 120 kg N/ha. Late nitrogen was applied at 10, 20, 30, and 40 kg N/ha as granular 34-0-0, granular 46-0-0, liquid 28-0-0, and liquid 46-0-0.

Yields were collected by straight cutting four rows from the middle of each plot. Grain protein was determined on whole grain samples using a commercial infra-red analyzer.

Results

Grain yield showed a response to pre-plant nitrogen applications up to 90 kg N/ha. No significant responses for yield to the late nitrogen applications were found.

Seed weight and test weight decreased as the pre-plant nitrogen rate increased. Late nitrogen application had no effect of seed weight or test weight. All samples met the minimum test weight for No. 2 CWAD.

Factorial ANOVA, LSD(0.05):Pre-plant N (P)=0.5;Late N (L)=).4; P X L = ns

Protein content of the durum grain increased as both pre-plant and late nitrogen rates increased. The late nitrogen application had a greater effect on increasing protein than did the preplant nitrogen, especially at low preplant application rates. The 40 kg N/ha treatment resulted in a significantly higher protein content than the 10 or 20 kg/ha rates (Table 1).

The larger pre-plant nitrogen rates, as recommended by soil test guidelines, produced large protein increases (Table 1).

Study 2: Effect of Late Nitrogen Source on Grain Quality

Factorial ANOVA LSD(0.05): N source (S)=0.3;Late N (L)=0.3, S X L = ns

All late nitrogen sources increased protein content above that of the control. The granular 34-0-0 and granular 46-0-0 produced a higher protein content than the two liquid nitrogen sources (Table 2). This is contrary to results reported elsewhere. Volatile losses of liquid nitrogen, or damage to the crop foliage may be responsible for this difference.

Economics

The preplant nitrogen applications contributed more to net return than did the late nitrogen applications, especially at the higher pre-plant rates. This was due to an increase in yield as well as an increase in protein. Late nitrogen contribution to the total return was small when pre-plant rates were optimal for yield.

Even though there was a positive return to nitrogen applied at flowering, the greatest return to the fertilizer input cost was realized from the pre-plant application. This relation held in the 1995-96 crop year in which durum protein premiums were high (Table 3).

- No. 2 CWAD prices by protein grade (less transportation and handling, Glenside Sask.) - 1995-96 crop year: 13.0% = $278/t; 13.5% = $284/t; 14.0% = $289/t.

- Fertilizer N = $0.77/kg