Nitrogen and Chloride Uptake by Irrigated Russet Burbank Potatoes1

Abstract

AbstractPotato production has become a major agricultural enterprise in the central sand plain of Wisconsin. However, little information is available on the effects of irrigation and fertilization practices on dry matter and N accumulation. This field study was established to determine the effect of reducing irrigation and fertilizer N on the dry matter, and the N and Cl in potatoes (Solanum tuberosum L., var. ‘Russet Burbank’) grown on a Plainfield loamy sand (Typic Udipsamment: sandy, mixed, mesic).Two basic treatments were used. The conventional treatment approximated current recommendations for irrigated potatoes and received 260 kg N/ha (as NH4NO3) in four applications and 45 an irrigation as 2.4 cm applications every 5 days. The improved treatment was intened to minimize leaching of NO3‐N. It received 170 kg N/ha in 10 applications (one as S‐coated urea and nine as NH4NO3) and 27.0 cm irrigation as 1.0 cm applications every 3 days. Chloride (as KCl) accompanied N on a 1:l weight basis. Plants were sampled weekly and analyzed for dry matter, total N, NO3‐N, and Cl.Plants accumulated 3 to 4 kg N/ha/day from 20 to 70 days after emergence. The maximum N uptake for the whole plant (tops and tubers) was 170 to 250 kg N/ha about 90 days after emergence. The maximum uptake of N in the tops was 125 and 80 kg N/ha in the conventional and improved treatments, respectively. Tuber yields and N uptake were similar between treatments with tubers containing 1.3 to 1.5% N most of the growing season and 130 to 140 kg N/ha (27 to 30 kg N/100 q) at harvest. Plants accumulated 115 to 145 kg Cl/ha, mostly in the tops (90 to 120 kg Cl/ha) with 25 to 40 kg Cl/ha in the harvested tubers.Nitrate‐N levels were low (<100 mg/kg) in tubers at all samplings. Nitrate‐N was >2,000 mg/kg in the tops during the first half of the growing season and accounted for 10 to 25% of the total N. Due to competitive antagonism, Cl reduced NO3‐N concentration in tops and petioles, and total N in tops and tubers.The results from this study show that tuber growth and N content were not appreciably affected by substantial reductions in the quantity of fertilizer N (90 kg N/ha) and irrigation (18 cm) applied although foliage dry matter and N accumulation were reduced. However, the additional effort required to effect this small saving in N fertilizer cannot currently be justified.