Aboveground and Root Decomposition of Cereal Rye and Hairy Vetch Cover Crops

Abstract

Hairy vetch decomposed faster than cereal rye. Hairy vetch released N within two weeks of termination. Biomass belowground decomposed more quickly than aboveground. Cover crop N release occurred earlier than maximum crop uptake due to late planting. Synchronizing cover crop decomposition and nutrient release with cash crop uptake can provide benefits to agroecosystems but can be difficult to implement. The objectives of this study were to quantify the aboveground and belowground decomposition and nutrient release of two cover crops, hairy vetch (Vicia villosa Roth) and cereal rye (Secale cereale L.), after termination with herbicides through a 16‐wk period during the cash crop growing season using litterbags and intact root cores. Plant Root Simulator probes monitored mineral N in the soil. Hairy vetch aboveground (k = 0.4505) and root (k = 0.6821) biomass decomposed at a faster rate than aboveground (k = 0.1368) and root (k = 0.1866) biomass of cereal rye. Hairy vetch had higher initial N content in aboveground (41.9 g kg–1) and root (16.5 g kg–1) biomass than cereal rye (11.5 and 8.3 g kg–1, respectively). Hairy vetch had a lower C to N ratio than cereal rye in both aboveground (9.52 vs. 34.72) and root biomass (17.31 vs. 40.31) contributing to decomposition differences. Hairy vetch rapidly decomposed after cover crop termination in the spring, therefore growers should consider delaying termination of this cover crop until close to cash crop planting to decrease the risk of N loss. Cereal rye residues decompose much slower and may also immobilize N because of its high C to N ratio. A better understanding of how aboveground and belowground cover crop characteristics influence decomposition will help to optimize cover crop nutrient release with cash crop uptake.

Particle Size Affects Nitrogen and Carbon Estimate of a Wheat Cover Crop

“…An ignored yet important management factor that can influence cover crop tissue C and N estimation is sample‐grinding size. A broad range of sample‐grinding size, ranging anywhere from >2 mm to pulverized have been reported in the literature (Jahanzad et al, 2016; Etemadi et al, 2017; Shelton et al, 2018; Sievers and Cook, 2018), but no agreement about which sampling size is the most appropriate has been reached to present. In a literature review, we randomly assessed 36 peer‐reviewed journal articles, which reported cover crop C and N concentrations (Table 1; in addition, see online version of article for supplemental material).…”

The Effect of Cover Crops on the Yield of Spring Barley in Estonia

“…In order to prevent the loss of accumulated N, it is recommended to sow subsequent crops as soon as possible after incorporating the biomass of leguminous cover crops with low C:N ratios, such as hairy vetch. Sievers et al [26] pointed out that most of the N in hairy vetch tissues is released in the first two weeks after termination. Therefore, it is susceptible to leaching out or denitrification if the following crop is not planted on time or it is not able to reach the growth stage where it could use the N from hairy vetch.…”

Cover Crops for Managing Stream Water Quantity and Improving Stream Water Quality of Non-Tile Drained Paired Watersheds

“…Nitrate-N leaching losses were 0.35 g N m 2 for corn followed by cereal rye compared to 2.51 g N m 2 for corn followed by hairy vetch [77]. Legume cover crops like hairy vetch have lower C:N ratio (16:1 or 22:1 as in our study) that might decompose at a faster rate [78]. This could result in release of available N from the cover crop biomass that is not synchronized with maximum N demand of the cash crop and result in runoff/leaching and might increase N loading to the headwater streams.…”