摘要
尼日利亚几内亚热带草原农业生态区有机施肥土壤有机碳、氮和微生物生物量的动态变化
作者(年代):S.O.Agele, S.O.Ojeniyi, S.K.Ogundare为评价农业废弃物与无机复合肥料NPK(市售含氮复合肥料)综合利用的效果，进行了田间研究。P. K)对土壤养分通量(源和汇)的影响。农业废弃物主要有:畜禽粪便(牛粪、家禽粪)、臭臭草、刺槐苗、印楝籽粉/饼、瓜壳等。这些材料分别以0(对照)、100%(即有机废物按推荐用量10t/ha施用)和70%推荐用量加上30%推荐用量的矿物肥料(NPK:400 Kg/ha)施用。以有机碳状态、净氮矿化和微生物生物量(微生物生物量C和N)库为指标测定的生物区系种群动态和土壤矿化度(土壤养分)在不同处理间存在差异。不同采样时间土壤无机氮释放量存在差异。土壤有机碳(SOC)和植物有效态氮(NH4-N和NO3-N)的时间动态趋势表明，种植后30天和60天达到峰值，之后逐渐下降。有机废物、有机废物加无机肥料(NPK)、无机肥料和未作处理的土壤有机碳平均值分别为1.94、1.68、1.36和1.38。在整个采样日期，SOC值在家禽粪便和neemseed cake中最高。SOC、NH4 +和no3 -的周转率平均值表明，有机修正后这些参数相对较大(1.94;19; 119) than in the unamended (1.36; 15.5; 54) soils. The values of NO3 - N plus exchangeable NH4 + N which constitutes plant available nitrogen (PAN) that were recovered were significantly higher for organically amended soils (550) andwastes applied at reduced rates combined with 120 kg/hamineral NPK (470) than the unamended control (277). NO3 - N plus exchangeable NH4 + N were relatively high at 30 and 60 days after planting, and this trend was consistent among the agricultural wastematerials applied. The higher values were followed by consistent decline afterwards especially at the end of the experiment (120 DAP). This indicates that the manures whether applied solely or at the reduced rates combined with 120 kg/ha mineral NPK had high mineralisation rates. Mineral N (NO3 - N plus NH4 + N) pools and % C microbial to C organic ratio were higher in the nutrient-rich organically amended soils which indicated that increased Nmineralisation were facilitated by higher amounts of SOC. The time changes in SOC, NH4-N and NO3-N contents was monitored, declines in the values of SOC with time was obtained. This time dependent declining in SOC is linearly relatedwith (Y= 0.18x + 1.07; R2 = 0.34)Asharp decline inNO3-Nwith time under organic amendment alone and the control The nature of the decline in NO3-N is related with time by a power function (Y = 48.084x-1.79; R2 = 0.91). The nature of the decline in NH4-N is related with time by a polynomial function (Y= -28.75x + 130.65x -57.25; R2 = 0.61).Although the trend of the effects ofwastes application on cfu were inconsistent however, the time dynamics of microbial population (cfu) follows trends obtained for SOC. The differences in the quality of the agricultural wastes measured in terms of C/N ratios differed and could have driven the observed temporal variations in soil chemical properties (soil organic carbon,mineralN andmicrobial biomass-C andN). The values of%Cmic: Corg (indicator of microbial activity in terms of the utilisation of organic carbon by the microbes and hence organic matter turnover rate) obtained could be indicative of greater access of nutrients for microbes.Although the%microbial carbon to organic carbon ratios were stable for all treatments, itsmag
