Phosphorus Fertilizer Affected Yields and Tillering of Four Wheat Cultivars in the Northern Great Plains.

Phosphorus (P) fertilizer application is important to optimize growth and development of spring wheat in the Northern Great Plains where, young plants are often susceptible to low available P in early spring. Deficient plants often do not show symptoms but tiller production, main stem development, can be variously impacted, depending on the cultivar. The objectives were to, (1) determine if wheat yields and grain quality response to P fertilizer differ between high and low yielding and protein varieties; (2) to verify if P effect on tiller initiation differs between cultivars of high and low tillering abilities. In 2016, four cultivars of wheat (Albany, Bolles, Linkert, and Prosper) were grown in Thief River Falls (TRF, MN) on a sandy loam soil, and in Carrington, ND (CREC) on a low available P (4 ppm) soil, and on a high P soil (12 ppm) loamy soil. Two P treatments were used at 0 and 40 lbs P₂O₅/ac at TRF, and 0 and 24 lbs/ac at CREC, to test crop response. The experimental design was a factorial RCBD with four replicates. Results showed that (1) P increased yields at a statistically significant level (p<0.05) at TRF and at CREC low P site. Yield increase was similar between cultivars, ranging from 6 to 7 bu/ac at TRF, and between 5 to 7 bu/ac at CREC low P site. Yield response was not significant at high P site at CREC. Even though a numerical yield increase of about 6.5 bushels was recorded for Bolles (low tiller production cultivar) at CREC high P site, compared to 1.5 bushels for Albany (high tiller cultivar) and Linkert, and 0 bushel for Prosper, P response was weak. (2) P fertilizer improved tiller initiation at TRF and CREC; (3) Grain P uptake ranged from 15.5 lbs/ac for the check compared to 20 lbs/ac in TRF. Grain protein and kernel weight did not respond to P.