Effect of different fertilizer resources on yield and yield components of grain maize (Zea mays L.) affected by tillage managements

Due to the development of sustainable agriculture and the reduction of utilizing chemical fertilizers, it is essential to use organic fertilizer. Organic matter is vital to soil fertility and its productivity. To maintain the level of fertility and the strength of soil, organic matter levels should be maintained at an appropriate level. Unfortunately, the level of organic matter in soil is generally less than 1%. One solution to increase the soil’s organic matter content is to use organic fertilizers such as animal manure, green manure, and vermicompost (Nuralvandy, 2011). As a correction factor, green manure can increase water supply and nutrient soil conservation (Tajbakhsh et al., 2005).
In order to assess the effects of fertilizer sources (green manure, cow manure, and chemical fertilizer) on maize yield and yield components (KSC 704) under tillage management, a field experiment was carried out at Zahak Agricultural and Natural Resource Research Station in two years (from 2013 to 2014). Before corn planting, barley was planted as green manure in the fall of each year. The experiment was conducted as a split plot arranged in a completely randomized block design with three replications. The main plots were tillage and no tillage, whereas the sub plots were: 1-barley green manure (without application of fertilizer), 2-barley green manure with applying 100% chemical fertilizer (NPK) to the barley during cultivation, tillering and stemming stages, 3- green manure with 2/3 of chemical fertilizer to the barley and 1/3 to the maize, 4- green manure with 1/3 of chemical fertilizer to the barley and 2/3 to the maize, 5- barley green manure with 50% animal and chemical manures, 6- barley green manure with 40 t ha-1 of animal manure, 7-control (non-fertilizer application). Corn was planted on 15 March each year. Phosphorus, potassium fertilizer, and animal manure were added to the soil as the base fertilizers. At full maturity, 10 plants were randomly selected and the plant height, the number of kernels per row, the number of rows per ear, the seed weight, the harvest index, and the ear length were measured, separately.
The results showed that in comparison with the first year, in the second year a significant increase was observed in plant height, ear length, number of kernel per row, weight of 100 seed weight, harvest index, and seed yield. The highest grain yield was obtained from the conventional tillage systems (mixing the fertilizer with the soil) with the mean of 4494.85 kg.ha-1. Other characteristics, except the number of row per ear, increased more in the conventional tillage than in the no tillage. Fertilizer sources were significant for plant height, ear length, number of kernel per row, weight of 100 kernels, harvest index, and seed yield. The highest grain yield was obtained from the sixth treatment (mix of animal, chemical and green manures) with the mean of 7018.5 kg.ha-1. The interaction of year, tillage and fertilizer sources indicated that the highest grain yield and 100 seed weight were obtained from the conventional tillage systems and from the 6th treatment (mix of animal, chemical and green manures) with the means of 9400.33 kg.ha-1 and 246 g, respectively. In the conventional tillage, microbial decomposition occurs faster than in the no tillage. Nutrients are released in vicinity of the plant roots and it can be placed conveniently at the disposal plant. In this way, the sixth treatment will achieve higher yield and better quality, because it can create diverse sources of essential nutrients for the plant; moreover, it can increase absorption capacity in corn.
In conventional tillage systems, where the sources of fertilizer are mixed with soil, the plant is placed in direct contact with the soil degrading bacteria, accelerating the fertilizers’ mineralization, and ultimately, improving the plant growth. Due to high soil density, the root growth limited during the first year of no tillage. Organic Food Systems (green manure and animal manure) provide the mineral food for plants. However, the low rate of mineralization in the early stages of root development can limit the nutrient availability. Nevertheless, these limits are removed over time. Integration of green manure, animal manure, and chemical fertilizer with conventional tillage not only strengthens the initial growth but it also accelerates the mineralization. In general, it can be concluded that application of green, animal, and chemical manures and conventional tillage for corn production can both reduce chemical fertilizer and environmental pollution and play a positive role in increasing the yield of maize.