Does Cover Crop Radish Supply Nitrogen to Corn?

Abstract

Core Ideas Radish as a cover crop does not supply nitrogen to the subsequent corn crop. Radish can result in neutral, negative, and positive effects on corn yield. Radish can have substantial nitrogen uptake in the fall, but effects on spring soil nitrogen are variable. Radish (Raphanus sativus L.) grown as a cover crop can accumulate a significant amount of N when planted by late summer. However, it remains unclear if the N in the radish biomass can supply N to a subsequent corn (Zea mays L.) crop. The objectives of this project were to: (i) measure radish growth and N uptake, (ii) determine the effect of radish growth on plant available N content in soil throughout the subsequent growing season, and (iii) determine the effects of radish on corn yields and response to N fertilizer. This study was conducted across nine site‐years in northeastern and southern Wisconsin, with radish planted mid‐August following winter wheat (Triticum aestivum L.) harvest. The experimental design was a randomized complete block, split plot design, with cover crop as the whole plot factor and N rate as the split plot factor. Radish N uptake was ranged from 19.7 to 202 kg ha−1 across all site‐years. The effect of radish on in‐season plant available N (PAN) content differed across growing seasons, with radish both increasing and decreasing PAN. The ANOVA and regression analysis showed mostly neutral effects of radish on corn yield, although corn yield increases and decreases following radish occurred. This research supports the use of radish as a trap crop for fall N, as environmentally meaningful yields of N were contained in plant biomass, but also demonstrates that radish has no N fertilizer replacement value to the subsequent crop.

Intersowing Cover Crops into Standing Soybean in the US Upper Midwest

“…Cover crops can also provide many soil health benefits, such as improving soil structure, increasing water infiltration, soil microbial activity, providing wildlife habitats, and scavenging of nutrients otherwise lost by erosion or leaching [16]. Radish has the ability to scavenge NO 3 -N from the soil, ranging from 19.7 to 202 kg ha −1 [19], and winter camelina can sequester residual soil NO 3 -N in the biomass throughout the fall and resume scavenging in the spring, and has been shown to accumulate from 24 to 59 kg N ha −1 in the above ground biomass [17]. If cover crops are not established early, limited growth will result and there are no added benefits.…”

Nitrogen Availability from Cover Crops: Is It Always about the C:N Ratio?

“…While it would be expected this C:N ratio and the often large amounts of N contained in the radish biomass would be advantageous and lead to a reduction in the optimum N rate for the subsequent corn crop, we never determined a "N credit" resulting from the radish (Ruark et al, 2018). In addition, there is more opportunity for different cover crop species to be planted, especially green manure cover crops that will supply N to the next year's corn crop (and result in less commercial N needed for optimal production).…”

“…The C:N ratio of total radish biomass (above-and belowground biomass) ranged from 10 to 19, and the total N uptake ranged from 20 to 200 lb N/ac. While it would be expected this C:N ratio and the often large amounts of N contained in the radish biomass would be advantageous and lead to a reduction in the optimum N rate for the subsequent corn crop, we never determined a "N credit" resulting from the radish (Ruark et al, 2018). Figure 1 shows the effect of radish across two different growing seasons in Sheboygan, WI (located in northeast Wisconsin).…”

Synergy and/or Antagonism in a Cover Crop Sequence: Rotational Effects on Rye in the Midwest

“…In sequential cover cropping, the biomass yield of radish increased in Cycle II. Radish is a N scavenging cover crop (Finney et al, 2016) whose residues decompose rapidly (Ruark et al, 2018) which might have increased N availability to winter rye. However, the phenomenon of yield reduction in winter rye recorded with the increase in the biomass yield of the first CC (oat, barley and berseem clover) does not seem to operate in this sequence.…”