Effect of mineral and organic fertilizers in the ryegrass yield (Lolium multiflorum L.): Dry matter yield and apparent N recovery

Abstract

A pot experiment with italian ryegrass was carried out to evaluate the N release from several fertilisers and organic amendments. The fertilizing materials were: chestnut fruit bark (CC), with 0.6% N, farmyard manure (EB), with 2.3% N, Beira Adubo (BA), a commercial organic amendment with 3% N; ammonium nitrate (NA), with 20.5% N; Entec (En), a fertiliser with a nitrification inhibitor, with 26% N; Fertigafsa (Fg) a 4-16-12 compound fertiliser, and control (T) without N fertilisation. All the fertilisers were applied at a rate equivalent to 200 mg N per kg of soil (< 2mm). A silt-loam soil with pH(H2O) 5.2 and 27 g kg^-1 of organic matter was used in the soil/fertiliser mixtures. A nutrient solution without N was added to all the pots. The crop was sown on the 1^stOctober, 2004. After crop emergence, the plants were thinned to 50 plants per pot. Six harvests of ryegrass were taken between November 9, 2004 and August 4, 2005. Nitrogen uptake and apparent N recovery (NAR) were also estimated after the determination of tissue N content. Total dry matter yields (6 cuts) were significantly different between treatments. Extreme values ranged between 1.7 g/pot (T) and 4.1 g/pot (NA). The higher N uptake was recorded in the NA treatment (167 mg N/pot), as well as the higher NAR (64%). Entec produced the lowest NAR (45%) among the mineral fertilisers. The organic amendments BA and EB showed similar NAR, 24 and 22%, respectively. The N released from BA, EB and En during the growing season was very low. The results stress the difficulties in properly managing this kind of fertilisers in annual crops with short growing cycles, where a N shortage could occur during important phases of crop development.