Distribution of Soil Carbon and Nitrogen in a Corn and Soybean Field.

Soil carbon and nitrogen are among the most important soil quality indicators and their availability in the soil will ultimately determine crop yield. The objective of this study was to assess the distribution of soil total carbon (TC) and total nitrogen (TN) at 0 to 60 cm depth in a corn and soybean field. The study was conducted at Lincoln University’s Freeman farm in a 10 acre field divided into 48 plots. The soil of the experimental site is Waldron silty clay loam. Soil samples were collected at four different depths: 0-10 cm, 10-20 cm, 20-40 cm and 40-60 cm in each of the 48 plots. After collection, the soil samples were air-dried and sent to a commercial laboratory for analyses of TC, TN and carbon to nitrogen (C/N) ratio. Results showed TC was about 0.90% in the first three depths and increased shortly to 1.1% in the last depth (40-60 cm). TN, however did not change and was about 0.10% in all depths. Consequently, the C/N ratio also changed and ranged between 9.05 in 0-10 cm to 9.18 in 40-60 cm depth. Variogram  analysis  showed that the sills (C_o+C) ranged between 0.042 m to 2.18 m for TC; 0.00003 m to 0.00044 m for TN and 0.37m to 0.65m for C/N ratio, suggesting a strong variability distribution of soil carbon and nitrogen in this field. Field maps also confirmed a non uniform distribution of TC, TN and C/N across the field.