Abstract
New technology makes it possible to apply organic fertilizers with higher precision, and organic producers want to know how to exploit these new possibilities to make their production more efficient. This study investigated the effect of band application (in different positions) of pelleted organic fertilizer, compared with broadcasting, on grain yield and weed density in spring oats (Avena sativa L.). Six microplot field experiments were carried out on silty clay and sandy loam in Sweden during the growing season of 2014–2016. In oats seeded at 25 cm row spacing, pelleted meat bone meal was band-applied at one of three distances from the crop row (0, 4, and 12.5 cm) and at two or three incorporation depths (1 and 4 cm on silty clay and 1, 4, and 6 cm on loamy sand). These treatments were compared with broadcast spreading, mineral nitrogen fertilizer, and an unfertilized control. On both soil types, fertilizer placement 4 cm from the crop and 4–6 cm incorporation depth gave the highest yield and crop nitrogen uptake. Yield in this treatment was 800 kg ha−1 higher on clay soil and 1,100 kg ha−1 higher on sandy loam compared with the same organic fertilizer applied by broadcasting, an 80–150% yield increase. On the sandy loam, distance from the crop row had a more significant effect on grain yield (p < 0.001) than soil incorporation depth (p = 0.07). On the silty clay, crop yield was significantly influenced by incorporation depth (p = 0.003) and distance from the crop row (p = 0.04). In five experiments, mineral N fertilizer equivalent (MFE) increased from on average 63% with broadcasting to 85% with placement 4 cm from the crop row and 4 cm incorporation depth. Weed biomass was significantly affected by fertilizer placement on the clay soil, with higher weed biomass with deeper incorporation (p = 0.045) and greater distance from the crop row (p = 0.049). On the sandy loam, there was a tendency for larger weed plants at greater distance from the crop row (p = 0.13) except when seeds and pellets were placed together, which gave the highest weed weight, probably due to lower competition from the crop in this treatment.
Highlights
Due to their physical properties, organic fertilizers are usually difficult to apply with good precision
Straw yield differed between soils, with on average 5,200 kg dry matter (DM) ha−1 on the sandy loam and 3,000 kg DM ha−1 on the silty clay
Straw yield was linearly correlated with grain yield and of similar magnitude, with a straw/grain ratio of 0.9 on the sandy loam and 1.2 on the silty clay
Summary
Due to their physical properties, organic fertilizers are usually difficult to apply with good precision. Pellets can be applied with machines that provide a uniform distribution in the field and are not as limited in time to perfect soil conditions as fertilizer products that require heavy machinery. Optimal Placement of Pelleted Fertilizer the same precision as seeds or granulated mineral fertilizers. The dose, time of application, and placement can thereby be much better optimized than for other organic fertilizers, which are often heavy, sticky, and difficult to distribute. Modern machinery equipped with RTK GPS and designed for seeding and weed hoeing with high precision is becoming more frequent in Swedish organic production. This gives farmers the possibility to place the pellets with high precision and many farmers want to know more about optimal placement. In other countries, other organic materials could be used
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