Site-Specific Nutrient Management for maize in upland and acid upland conditions

The soil fertility constraints in specific sites or farms are essential information needed to prescribe adjusted fertilizer rates to satisfy the requirement of high yielding corn. This investigation was conducted to determine and quality the yield potential of maize under upland and acid upland conditions, and to develop, evaluate and disseminate a new site-specific nutrient management (SSNM) approach and best crop management practices for maize under these conditions. Thirty-nine on- farm trials were conducted from 2005-2007 wet and dry cropping seasons in Isabela and Bukidnon involving upland and acid upland areas, respectively. The soil properties of the farms used in the on-farm trials at Isabela with favorable texture of clay loam are the following: the soil pH are strongly acidic (5.5) to neutral (7.1); total N is very low (0.05%) to medium (0.17%); available P (Olsen method) is moderate (7ppm) to high (37 ppm)while Bray P2 is low (6.95 ppm) to high (36 ppm); exchangeable K is moderately low (0.24 cmol/kg) to high (0.90 cmol/kg) while Ca and Mg are medium to high. For the clayey farms of Bukidnon, the soil chemical properties are as follows: strongly acidic to mildly alkaline pH (5.5-7.6) medium to high organic C (2.3-2.7%); medium to high total N (0.20-.27); high available P (Olsen, 23-33 ppm) and low to moderate Bray P2 (2.4-10.9 ppm); moderately low to very high K (0.24-1.49 cmol/kg) ; low to medium Ca (3.1-5.1 cmol/kg) and very low to medium Mg (0.47-1.76 cmol/kg). The climate in Isabela is Type 2 which has no pronounced wet season but relatively dry from February to April while Bukidnon has a Type 3 climate which has seasons that are characterized as not very pronounced but dry from November to April and wet during the rest of the year. During the first two cropping seasons (2005-2006); fertilizer omission plots (-N,-P, and -K) was set up, as well as fully-fertilized treatment with high N,P and K fertilizer applications to avoid nutrient limitation and compared with the farmers' fertilizer practice (FFP). Three maize varieties were tested under two planting densities (75cm x 20cm and 60cm x 20cm). The N, P2O5 and K2O8 rates used were 200, 120 and 120 kg/ha, respectively. Lime was applied areas where the soil pH falls below 5.3. For the succeeding two cropping seasons (2006-2007), the treatments involved five levels of fertilizers: NPK 1(2-N splits), minus N, minus P, minus K and NPK 2 (3-N splits) and 3 planting distances (75cm x 20cm, 60cm x 25cm and 60cm x 20cm). Nitrogen was applied in two splits (basal and V6-V8 stage) and three splits (basal, V6-V8 and V10-V12, stages). Only the farmer's chosen corn hybrid was used. Yields greater than 9t/ha are possible in Isabela, while yields of 8-9t/ha can be attained in Bukidnon, both under favorable rainfall condition. This could be achieved with optimized plant population and non-limiting nutrient management. Nitrogen is the most limiting factor on both province followed by phosphorus and potassium but higher rates of P and K fertilization is required in Bukidnon. Effective plant population of about 65,000 to 78,000 plants/ha must be maintained to have reasonable yield. During the 2006-2007 dry season cropping, higher benefits in terms of net returns were assessed from the initial evaluation of the first adjusted fertilizer NPK rates developed and derived from the result of the NPK and omission plot experiments and initial soil analysis obtained during the first two cropping seasons. Grain yields in Bukidnon were almost similar for the dry and wet season while higher yields were realized in Isabela during the wet season. For the nitrogen management technology, it was noted that in both provinces, 2N split application was better than the 3N split application during the wet season while the 3N split application showed advantage in yield over the 2N split during the dry season, cropping, however the difference is not significant. Initial results using the leaf color chart (LCC) indicated that this technology could be used in real time nitrogen management for corn to improve the nitrogen use efficiency whenever water is available for irrigation. It was also observed that application of fertilizer nitrogen at a rate of 40 kg per ha will result to a yield response equivalent to one ton per ha based on the agronomic efficiency of 25 kg grain increase/kg N added.