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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #207290
Title: SOIL COMPACTION AND POULTRY LITTER EFFECTS ON FACTORS AFFECTING NITROGEN AVAILABILITY IN A CLAYPAN SOIL

Author
item PATTHRA, PENGTHAMKEERATI - UNIVERSITY OF MISSOURI
item MOTAVALLI, PETER - UNIVERSITY OF MISSOURI
item Kremer, Robert
item ANDERSON, STEPHEN - UNIVERSITY OF MISSOURI

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2007
Publication Date: 3/23/2007
Citation: Patthra, P., Motavalli, P.P., Kremer, R.J., Anderson, S.H. 2007. Soil compaction and poultry litter effects on factors affecting nitrogen availability in a claypan soil. Soil & Tillage Research. 91(1):109-119.

Interpretive Summary: Soil structure is an important characteristic because it reflects the physical condition related to cultivation (“tilth”) and the manner in which soil particles are arranged (aggregated) that define soil porosity, which is the ability to hold and conduct water and air necessary for microbiological processes and plant growth. Because timely planting and harvesting of crops are affected by prevailing weather conditions, moist or wet soils are often subjected to the weight of farm machinery traveling over the soil surface. Soils may become compacted, which weakens soil structure and leads to reduced water infiltration and aeration, reduced microbial activity involved in nutrient cycling and a poor seedbed for crop root penetration. Nitrogen that is not made available to plants by microorganisms in compacted soils may readily move into the environment via surface water runoff and gaseous emissions. We investigated the effects of soil compaction on microbial activity by measuring nitrogen mineralization as the quantity of ammonia (NH4+) transformed by microorganisms from organic components (poultry litter, a good source of organic nitrogen) in a soil under corn production in North Central Missouri. In a laboratory study, field-collected soils were either amended with poultry litter (28 g per kg of soil) or not, then artificially compacted by increasing the bulk density (dry soil mass per unit volume) using a hydraulic press, moistened, and incubated at room temperature. Periodic sampling showed that nitrogen mineralization decreased as bulk density (compaction) increased and as soil porosity (pore or air spaces) decreased. Addition of poultry litter, however, increased nitrogen mineralization in compacted soils, suggesting that organic substances in the manure may offset compaction by stimulating microbial activity with readily available nutrients. A subsequent field study in which soil was either amended with poultry litter (about 8.4 tons per acre) or recieved no litter, and where soil in half the field was compacted using a tractor-pulled water wagon containing about 500 gallons of water, also showed that nitrogen mineralization decreased as compaction increased. Available nitrogen (NH4+) and overall nitrogen mineralization were increased by adding poultry litter in the upper soil layer only early in the corn-growing season. Poultry litter had no effect on nitrogen in soil during the remainder of the season likely due to uptake by growing corn plant roots and low moisture in lower depths of the soil. The results suggest that incorporating poultry litter may alleviate soil compaction’s adverse effects on nitrogen mineralization by providing more nutrients for microbial activity. However, these effects may not be as obvious under field conditions of limited moisture and actively growing crops. This information is important for scientists, extension personnel, and farmers because it will be useful in managing soil compaction and nitrogen fertilization effects on crop productivity, which could involve the use of an abundant agricultural resource, poultry litter, as an effective soil amendment.

Technical Abstract: Soil compaction may affect N mineralization and the subsequent fate of N in agroecosystems. Laboratory incubation and field experiments were conducted to determine the effects of surface soil compaction on soil N mineralization in a claypan soil amended with poultry litter (i.e., turkey excrement mixed with pine shavings as bedding). In a laboratory study, soil from the surface horizon of a Mexico silt loam soil was compacted to four bulk density levels (1.2, 1.4, 1.6 and 1.8 Mg m-3) with and without poultry litter and incubated at 25°C for 42 days. A field trial planted to corn (Zea mays L.) was also conducted in 2002 on a Mexico silt loam claypan soil in North Central Missouri. Soil was amended with litter (0 and 19 Mg ha-1) and left uncompacted or uniformly compacted. Soil compaction decreased total soil inorganic N by a maximum of 1.8 times in the laboratory study; this effect was also observed at all depths of the field trial. Compacted soil with a litter amendment accumulated NH4+-N up to 7.2 times higher than the noncompacted, litter-amended soil until day 28 of the laboratory incubation and in the beginning of the growing season of the field study. Ammonium accumulation may have been due to decreased soil aeration under compacted conditions. Application of litter increased soil N mineralization throughout the growing season. In the laboratory study, total soil inorganic N in unamended soil was negatively correlated with soil bulk density and the proportion of micropores, but was positively related with total porosity and the proportion of macropores. These results indicate that soil compaction, litter application and climate are interrelated in their influences on soil N mineralization in agroecosystems.