Estimation of the amounts of livestock manure, rice straw, and rice straw compost applied to crops in Japan: a bottom-up analysis based on national survey data and comparison with the results from a top-down approach

We estimated the application of cattle, swine, and poultry manure and of rice straw and rice straw compost for seven crop groups (paddy rice, upland crops, vegetables, orchards, tea, forage, and fodder) from a bottom-up analysis of government questionnaire data. Vegetable crops consumed the most manure and received the largest amount of swine and poultry manure and of rice straw compost, and the second-highest amount of cattle manure. Paddy rice received the least manure, and depended mainly on organic matter from non-composted rice straw. Fodder (timothy (Phleum pratense. L.), etc.) and forage (dent corn (Zea mays L.), etc.) crops used for cattle husbandry consumed the most cattle manure; however, fodder crops received only one-quarter of the cattle manure received by forage crops. We hypothesized phosphorus (P) is not lost during composting, then estimated the amount of raw materials for livestock manure inversely from applied livestock manure P and carbon (C)nitrogen (N):potassium (K):P ratio of kinds of livestock excreta. More than half of livestock excreta (6224 Gg C, 589 Gg N, 90 Gg P, and 278 Gg K) was utilized for manure. However, manure applied (2300 Gg C, 158 Gg N, 90 Gg P, 154 Gg K) was lower than in a previous study based on a top-down analysis (161 Gg N, 92 Gg P), possibly because mainly poultry excreta (520 Gg C, 75 Gg N, 11 Gg P, 13 Gg K) and a considerable amount of livestock excreta (3654 Gg C, 353 Gg N, 53 Gg P, 174 Gg K, not including loss during storage) were not utilized. A newer survey to grasp the present state of fertilization done by the government could update our assessment of the use of livestock excreta for crop production based purely on top-down approaches.