Effect of compost rates at different depths on some chemical properties and productivity of soils

Two field experiments were conducted on clay loam soil during the two successive seasons, summer season 2013 using maize plants and winter season 2013/2014 using wheat plants at El-Gemmeiza Agricultural Research Station, El-Gharbia Governorate to evaluate the effect and residual effects of compost rates placed in 20 and 40 cm depths, arranged in parallel orientation with respect to one another and spaced at 3 m apart or placed on the surface soil layer as well as the control on improving some soil chemical properties and availability of some nutrients either macro or micro, and the productivity of yield and yield components of maize and wheat plants. Furthermore, economical analysis was done by calculating the net income and investment ratios to determine the economical treatment. The experiments were conducted in a split plot in a randomized complete block design (RCBD) with three replicates. Results can be summarized as follows:(1)- All treatments slightly decreased the soil reaction (pH). Furthermore, all treatments caused progressive increases in soil salinity (EC) and total soluble salts (TSS) for the two soil depths (0-20 and 20-40cm) in the two growing seasons. Also, soluble cations and anions slightly increased with all treatments. While, SAR values were decreased compared with the control for the two soil depths in the two growing seasons. (2)- Generally the application depth and the addition rates of compost clearly enhanced the nutrient statues of the investigated soil.( 3)- Organic carbon (O.C, %) and C/N ratio were slightly increased in surface and subsurface soil layers as a result of the application depth and the addition rates of compost. (4)- All treatments led to markedly increases in the available macronutrients (N, P and K) and available micronutrients (Fe, Zn, Mn and Cu) of the soil at the two soil depths in the two growing seasons either with mole depth or compost rates.( 5)- The yield and yield components of maize and wheat positively responded to all treatments compared with the control. The highest values of yield and its components for maize and wheat plants were obtained by the addition of 10 ton compost fed ^-1in 40 cm mole depth. The highest grain yield of maize plants increased to 68.46 %, also, the highest grain and straw yields of wheat plants increased to 70.27 and 91.67 %, over the control, respectively. (6)- According to the economical analysis, the application of 10 ton compost fed^-1in 40 cm mole depth was the best treatment compared with the other treatments, since it gave the highest net income (12346.38 L.E fed^-1.). While, the lowest values were always incorporated with control (10 cm surface depth without any applications of compost). (7)- Therefore, it is more useful to use those treatments (compost rates at different depths) to get a markedly improve in both chemical properties and nutrients which reflect on higher yield incorporated with high net income, as well as to substitute a part of chemical fertilizers by using compost to minimize the pollution resulted from the intensive use of it.