Two field experiments were conducted on clayey soil during the two successive seasons, i.e. winter season 2018/2019 using wheat plants and summer season 2019 using maize plants at EL-Gemmieza Agriculture Research Station - Agricultural Research Center (ARC) - El Gharbiya Governorate - Egypt (Middle Delta region 30º 43- latitude and 31º 47- longitude). The experiments were designed in a randomized complete block design with three replicates to prediction of the most combination of compost, nitrogen and phosphorus fertilizers and its effects on some soil properties and its productivity of crops. Furthermore, economical evaluation was done by calculating the net revenue to determine the most economical treatment.Thirteen treatments having different compost (C), nitrogen (N) and phosphorus (P) were used to cover all possible combinations of these applications as well as control (without any addition). The results were shown in a triangle diagram using a special computer program.
The obtained results can be summarized as follows:
1- The individual compost treatment was more effectiveness on reducing Db and increasing E and e than N and P treatments, as well as Hydraulic conductivity and soil moisture content at harvesting were increased with all treatments compared with the control of the two soil depths at the end of the two seasons.The maximum kh value was obtained by using 100% compost or 90% compost + 10% nitrogen. Also, interaction between C, N and C, P were more effective on increasing kh.
2- Water consumption (CU) decreased, but water use efficiency (WUE) increased with both individual and combined applications of C, N and P in the two season. The lowest CU values were recorded with the individual compost treatments in the two seasons.
3- All treatments of C, N and P and their combinations led to decrease in soil pH and increased soil EC and the soil content of total NPK at the two soil depths in the two seasons compared with control.
4- The addition of 100% compost (C) gave the highest O.C content, where C was more effective upon increase O.C than N and P which took the order C < N < P. While, the maximum C/N ratio values were recorded under the treatment consist of 50% C + 50% P in the two seasons.
5- Grans yields and growth characters of wheat and maize plants increased with all the additions of C, N and P alone and in combinations compared with the control, where the highest values were recorded with the treatment consists of 50%
C +50% N.
6- The obtained results in this study show it is more useful to use C, N and P and their combinations to get a markedly improve in soil physical and chemical properties which reflect on highest yield in incorporated with high net revenue. Where, the highest net revenue (7636.84 LE fed-1) was recorded by using the treatment consists of 50% C + 50% N in the two seasons.