Understanding Soil Spatial Variability for Sustainable Forage Corn Production in Eastern New Mexico.

Variability of soil properties at the field and farm scale may affect soil biogeochemical and hydraulic properties thereby influencing sustainable crop production. Understanding spaciotemporal variability has become more critical as climate change, and soil quality degradation has challenged agricultural sustainability. The objective of this study is to evaluate field-scale soil variability in an irrigated forage corn field in conjunction with the effects of row spacing, corn silage cutting height, and cover cropping treatments on soil quality. We hypothesize that increasing stubble height, decreasing row spacing, and integrating cover crops will reduce soil erosion, retain soil moisture and nutrients, and improve forage quality. This study was established on an agricultural field near Clovis, NM under a half-circle irrigation pivot. The study area was divided into seven spans with two different row spacings (15” and 30”), cutting heights (6” and 18”), and cover crop (cereal rye [Secale cereal L.] and Austrian winter pea [Pisum sativum L.] mixture) treatments. Spans 1-3 received cover crops, whereas spans 4-7 had row spacing and silage cutting height treatments. Eighty randomly selected soil samples were collected before corn planting and after harvest in 2017. All soil samples were analyzed for soil organic carbon (SOC) and nitrogen (N) components. Average potentially mineralizable carbon before planting was 19.54 mg-kg^-1, whereas total C and N was 1.29% and 0.13% respectively. Soil inorganic N before planting and after harvest were 9.38 mg-kg^-1 and 2.53 mg-kg^-1. Semivariogram models run for inorganic N before planting (range = 135.69m) and after harvest (range = 116.99m) revealed a decrease in spatial range and increase in spatial dependence as crop grew. The long-term goal is to increase plant residue covering the soil surface to aid in moisture retention, soil health improvement, and ultimately increase agricultural productivity and sustainability in the region.