Marginal upland shave low crop productivity due to poor soil fertility and continuous degradation. The study evaluated the effects of various organic based fertilizers on the growth and yield performance of corn; determine the appropriate combination of organic and inorganic fertilizers for optimum corn yield; and assess changes in soil properties. The experiment was laid out in Randomized Complete Block Design (RCBD) in three replications with seven treatments: T0 = (0-0-0); T1 = 1 t ha-1 evans + 45-30-30 kg N, P2O5 K2O ha-1; T2 = 15 t ha-1 wellgrow + 45-30-30 kg N, P2O5 K2O ha-1; T3 = 15 t ha-1 chicken litter;T4 = 10 t ha-1 chicken litter + 45-30-30 kg N, P2O5 K2O ha-1; T5 = 15 t ha-1 vermicast; and T6 = 10 t ha-1 vermicast + 45-30-30 kg N, P2O5 K2O ha-1. Most agronomic characters as well as yield and yield components of corn were significantly affected by the treatments. Application of 10 t ha-1 chicken litter + 45-30-30 kg N, P2O5 K2O ha-1 markedly enhanced height, leaf area index and stover yield of corn comparable with 10 t ha-1 Vermicast + 45-30-30 kg N, P2O5 K2O ha-1. This treatment produced significantly higher grain yield in two croppings due to bigger ears and heavier seed weight over the untreated control and appeared the most promising combination. No remarkable changes in soil properties were noted except for an increase in available P and exchangeable K. Supplementation of organic with inorganic fertilizers is necessary to enhance productivity of marginal uplands.

Energy analysis is not usually given much emphasis in crop production despite the latter's huge dependence on oil and fuel. This study was conducted for two cropping seasons to assess whether the use of various nutrient sources can increase yield, energy productivity, and use efficiency of lowland rice (PSB Rc18). All production inputs and activities were accounted and energy analysis was done using energy coefficients adopted by previous researchers. Parameters on grain yield, energy expenditures, energy productivity, efficiency, and intensity were taken. Rice applied with organic fertilizer from unenhanced composted cow manure (UECM) yielded significantly higher by 61% and 18 % than the untreated control and the full inorganic treatment, respectively. Quantum and organic nutrient sources spent 69.18-71.79 liter diesel oil equivalent (LDOE) ha which is 2-3 times -1 lesser than the use of sole inorganic or combined with organic nutrient sources (142.13-225.74 LDOE ha ), thus giving significantly higher energy productivity -1 and efficiency. Unenhanced composted cow manure was the most productive and efficient in terms of energy use by 1.59 and 3.73 times over the control and full inorganic treatment, respectively. Energy spent to produce a ton of unmilled rice was markedly reduced by 53% from organic fertilization due to lower energy intensities (15.95-25.16 LDOE t grain) than inorganic treatments (36.50-60.89 -1 LDOE t grain). Hence, at this time of energy crisis and climate change, organic -1 farming which includes use of quantum enhancers is a potential option in improving energy resource effectiveness of PSB Rc18.

Three species of legumes such as mungbean, cowpea, amd bushbean were incorporated into the soil at flowering to later stages of growth namely; after 1st, 2nd, and 3rd priming operations. These were followed by two croppings of upland rice. Significantly lower soil bulk densities were obtained after the first crop of rice when mungbean and bushbean herbage were used as green manure. The pH, O.M., P and K contents of the soil planted to rice were not markedly affected by the species and timing of field legume incorporation. Interaction effects between the two variables on O. M. and pH were noted after the harvest of the first and second crops of rice, respectively. Most of the growth and yield parameters of both crops of rice were not significantly influenced by the treatments involved. [his indicates the feasibility of modifying the usual practice of green manuring at flowering stage to later stages of growth using grain legumes without necessarily sacrificing their expected yields. Cowpea was the most suitable green manure crops for upland rice. Its use resulted in the highest combined net income for two croppings of rice, generating PhP 48,698.98 ha-1 or PhP 2.12 income per peso invested. Regardless of field legumes used, herbage incorporation after the first priming generated an income of PhP 1.56 per peso invested while green manuring at flowering stage gave only PhP 0.69.

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Nutrient management adopting various decision-support tools plays a key role in obtaining better rice yield. Thereby, three nutrient management strategies; i.e., Regional Soil Laboratory (RSL), Rice Crop Manager (RCM), and Farmers' Fertilizer Practice (FFP) for lowland rice production were tested. The experiment was laid out in an RCBD with four treatments and three replications. The treatments were T0 = Control; T1 = RSL; T2 = RCM; T3 = FFP. Results revealed that rice plants under FFP applied with higher amounts of N, P2O5, and K2O significantly headed and matured late than unfertilized control and RSL but no significant difference from that of RCM. Rice plants under RCM developed significantly more productive tillers when compared to all other treatments except for RSL which produced a similar number of productive tillers. Rice plants under RSL obtained significantly higher grain yields but were comparable with RCM. The highest gross margin and highest return on investment (ROI) were obtained in plants under RSL with Php 65,226.73 ha -1 and 90.55%, respectively while the control plants obtained the lowest gross margin of Php 9,294.44 ha -1 . The nutrient requirements of NSIC Rc176H should follow both RSL and RCM for excellent growth, better yield, and higher income. Therefore, RSL and RCM nutrient management decision tools are strongly recommended for rice farmers' adoption to assure of achieving better yield, high gross margin, and equitable ROI under irrigated lowland ecosystems.