Saturday, 15 July 2006

Effects of Phosphorus-Based Manure Compost Applications on Corn Production and Soil Phosphorus Accumulation in Upland Andosol.

Toyoaki Ito, Teppei Komiyama, and Masahiko Saigusa. Field Science Center, Graduate School of Agricultural Science, Tohoku Univ, Yomogida 232-3, Naruko, Japan

In Japan, available Phosphorus (P) of arable lands (soil test P) is increasing because of excessive application of inorganic phosphate fertilizer and manure compost. Manure compost application to meet Nitrogen (N) requirements of crops (N-based application) elevates soil P levels because the N/P ratios of manure compost are much lower than those required by crops. Through surface runoff and subsurface flow of P output, soil P accumulation can cause eutrophication of lakes, rivers and the sea (Sharpley, 1999). P-based manure compost application system should be established to prevent soil P accumulation and maintain crop yields. Bahman et al. (1999) demonstrated the effectiveness of P-based manure compost application on corn production and suppression of soil test P increase, but its effectiveness in Andosol has not been evaluated. In Japan, Andosols, which are derived from volcanic ash and show high P-fixation, cover more than half of upland fields. In this study, effects of P-based manure compost application on yields of dent corn (Zea mays L.) and soil P accumulation were evaluated in upland Andosol using two types of manure compost (cattle and poultry manure composts). Field experiments were conducted in 2004 and 2005 at the FSC, Graduate School of Agricultural Science, Tohoku University, Japan. The experimental field had Melanic Andosol. Treatments were the following: 1) N-based cattle manure compost application (N-based CC), 2) P-based cattle (P-based CC), 3) N-based poultry (N-based PC), 4) P-based poultry (P-based PC), 5) Chemical fertilizer (N-P-K = 150-65-62 kg ha-1) (CF), 6) No phosphate fertilizer (No-P), 7) No compost and fertilizer (Check, CK). The bioavailable N in manure compost was assumed as 30% of total N according to NGRI (1983) and Tanahashi et al. (2004). Bioavailable P in manure compost was determined by the sequential extraction method of Frossard et al. (1996). The sum of water and 0.5 M NaHCO3 extractable inorganic P was estimated to be bioavailable P according to Ito et al. (2004). In N-based treatments, compost application rates were decided to supply 150 kg N ha-1 as available N. In P-based treatments, 65 kg P ha-1 as available P from the manure composts was supplied and additional N fertilizer was applied because available N from manure composts was insufficient to supply 150 kg N ha-1. Dent corn (Zea mays L.) was planted at the rate of 71,000 seeds ha-1 . Plants¢ dry weight and N and P uptakes were measured. Surface soil (0-30 cm) samples were collected from all plots at harvest. Soil test P values were assessed using Merlich-3 extraction method (Merlich, 1984). Nutrient contents of manure composts (based on dry weight) were not so different between the two years. Cattle and poultry manure composts contained almost the same amounts of available P (7.7-9.4, 8.3-10.4 g P kg-1, respectively). However, the two composts had considerably different ratios of available P to total P (75-76%, 32-39%, respectively). The dry matter yields in all manure compost treatments were greater than those of the CF treatment. Especially, the yield in N-based PC was significantly (p<0.05, Tukey¢s HSD) greater than CF in 2005. Total P uptakes of corn in all manure compost treatments were greater than that of the CF treatment, suggesting that available P in the manure composts was more effective for corn growth than phosphate fertilizer, or that other P fractions of manure composts were also effective for corn. Soil test P values assessed using the Merlich-3 method in surface soil (0-30 cm) at harvest in 2005 were significantly higher in N-based treatment of N-based CC and N-based PC compared with No-P treatment. Soil test P values were not significantly higher for P-based treatment of P-based CC and P-based PC than for No-P treatment. Soil test P values at harvest in 2005 were positively correlated with the total amount of available P added by composts or fertilizer for two years (r=0.976**, n=7). These results demonstrate that P-based manure compost application system was effective from the perspective of both sustainable corn production and suppression of bioavailable soil P increase in upland Andosols with high P-fixation capacity.

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