DOI: 10.5061/dryad.5qr62
title: Data from: Effects of fertilizer on inorganic soil N in East Africa maize systems: vertical distributions and temporal dynamics

description: Fertilizer applications are poised to increase across sub-Saharan Africa
 (SSA), but the fate of added nitrogen (N) is largely unknown. We measured
 vertical distributions and temporal variations of soil inorganic N
 following fertilizer application in two maize (Zea mays L.)-growing
 regions of contrasting soil type. Fertilizer trials were established on a
 clayey soil in Yala, Kenya, and on a sandy soil in Tumbi, Tanzania, with
 application rates of 0–200 kg N/ha/yr. Soil profiles were collected (0–400
 cm) annually (for three years in Yala and two years in Tumbi) to examine
 changes in inorganic N pools. Topsoils (0–15 cm) were collected every 3–6
 weeks to determine how precipitation and fertilizer management influenced
 plant-available soil N. Fertilizer management altered soil inorganic N,
 and there were large differences between sites that were consistent with
 differences in soil texture. Initial soil N pools were larger in Yala than
 Tumbi (240 vs. 79 kg/ha). Inorganic N pools did not change in Yala (277
 kg/ha), but increased fourfold after cultivation and fertilization in
 Tumbi (371 kg/ha). Intra-annual variability in NO−3-N concentrations (3–33
 μg/g) in Tumbi topsoils strongly suggested that the sandier soils were
 prone to high leaching losses. Information on soil inorganic N pools and
 movement through soil profiles can h vulnerability of SSA croplands to N
 losses and determine best fertilizer management practices as N application
 rates increase. A better understanding of the vertical and temporal
 patterns of soil N pools improves our ability to predict the potential
 environmental effects of a dramatic increase in fertilizer application
 rates that will accompany the intensification of African croplands.
description: Bi-Weekly soil N in
 KenyaBi-weekly potassium
 chloride-extractable N in soils collected 0-15cm in field sites in Yala,
 Kenya. Data span 26-Apr-2012 to 4-Dec-2013.WeeklyKCl_KE.csvBi-Weekly soil N in TanzaniaBi-weekly potassium chloride-extractable N in soils (0-15cm) in Tanzania plots. Collection dates span 9-Nov-2012 to 2-Apr-2014.WeeklyKCl_TZ.csvInitial soil data from depth profiles in Kenya and TanzaniaInitial soil NO3-N, NH4-N and pH from 0-400 cm depth profiles.Initial_DP_KETZ_zeroN.csvSoil depth profile data from Kenya and Tanzania after 2 years of cultivationSoil NO3-N, NH4-N, pH from maize trials in Kenya and Tanzania collected after 2 years of cultivation in unfertilized (0N) and fertilized (200 N) plots.Yr2_DP_KETZ_zero200.csvSoil depth profile data from Tanzania after 2 years of cultivation (organic vs. inorganic comparison)Soil NO3-N, NH4-N, and pH in Tanzania plots receiving either 75 kg of N as inorganic fertilizer or 75 kg N as organic fertilizer from Gliricidia sepium leaves. Depth profiles collected after 2 years of maize cultivation.Yr2_DP_TZ_Glir75.csvDepth profile data from Kenya after 3 years of maize cultivationSoil data from depth profiles collected in Kenya plots after 3 years of cultivation. Note that there are fewer depth categories. Also, plots were bulked by fertilizer treatment, so there is no replication in this data set. These data were used for qualitative comparison to the other profiles, but not in statistical analyses.2014_CIAT_DP.csv