ABSTRACT


Maximiliano Martínez V.1 y Elías Letelier A.1
 
Since 1967 a permanent trial has been carried on in La Platina Experimental Station. Two rotations and two level of nitrogen are compared factorially. Rotations: 1. Three years of red clover/Dactylis. Two years of turnips (in winter) and corn (in summer) 2. Every year turnips (in winter) and corn (in summer). Fertilizer treatments: a) 300 Kg of nitrogen/ha to turnips and corn (600 Kg/ha/year). b) Without nitrogen. The pasture was divided in two parts: in the first one, the cuttings were composted and recycled to the corresponding crops of turnip and corn; in the second part, the cuttings were not returned.After completing seven times each of the rotations the average yields of treatmentswere:____________________________________________________________________________________________________________________________Tratamientos Nabo, Ton/ha Maiz, Ton/ha ______________________________________ _____________________________________ Cultivo continuo Rotación con pradera Cultivo Continuo Rotación con praderas____________________________________________________________________________________________________________________________N0 s/devolución cortes 8,20 12,93 27,04 38,36N0 c/devolución cortes __ 17,82 __ 56,08N300 s/devolución cortes 51,82 51,73 86,58 105,69N300 c/devolución cortes __ 56,58 __ 109,63____________________________________________________________________________________________________________________________Yields of the pasture mixture were very slighthy affected by treatments. Yields of the second year of crops in the rotation with pasture (turnip and corn) were very similar to the first year.
An analysis of the results points to the following conclusions:
-The main effect was nitrogen
-The inclusión of pastire had an important effect on the yield of corn. This effect is partially due to the nitrogen fixed by the pasture and recycled through the composted cuttings, but an important part of it is due uknown causes.
-The pasture effect on turnip is much lower and the whole of it can be attributed to nitrogen recycled in the compost.
The continuous cropping sydtem fertilized with nitrogen yields a higher total production of food diretly usable by man, than the rotation system.
Key words:
1Ing. Agr., Programa Fertilidad y Manejo de Suelos, e Ing. Agr., Coordinador del Area de Recursos Ambientales del INIA, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.