Nicasio Rodríguez S.1, Jorge Chavarría R.1, Ciro Belmar N.1 y Carmen Lobos S.1
The effect of three phosphorus sources: diammonium phosphate (DAP 20.5% P), triple superphosphate (TSP 20.5% P and 1.0% S) and simple superphosphate (SSP 10.9% P and 11.0% S) on wheat production on an irrigated sandy soil, were studied. Three phosphorus rates were applied: 17.5, 35.0 and 52.5 kg ha-1. The sulphur content in the soil was 0.7 mg kg-1 which implies a nutritional deficiency for high-yield wheat crops. When SSP was used rates of: 0, 17.6, 35.2 and 52.8 kg ha-1 of S were applied to the soil. The grain yield response to phosphorus applied was lower with DAP and medium with TSP and higher with SSP, with a maximun of 25.8 and 33.0 qqm ha-1, respectively. When SSP were used a significant yield increase was observed with the applied rates of 52.5 kg ha-1 of P and 52.8 kg ha-1 of S with a yield of 55.5 qqm ha-1. The grain yield increase is attributed to the effect of the sulphur applied. The soil extractable sulphur in the soil test was 0.7 mg kg-1 S, with a high possibility of sulphur deficiency. A linear regression between grain yield and applied sulphur were obteined as follows: Y = 24.635 + 0.467037 S and R2 = 0.706 (P < 0.01). Also, a linear regression were obtained between grain yield and sulphur concentration in the leaves; sulphur applied to the soil and sulphur concentration in the wheat Ieaves.
Key words: wheat, fertilizer, phosphorus, sulphur, irrigated sandy soil.
1 Estación Experimental Quilamapu (INIA), Casilla 426, Chillán, Chile.