Rice Yield and the Fate of Fertilizer Nitrogen as Affected by Addition of Earthworm Casts Collected from Oilseed Rape Fields: A Pot Experiment

Abstract

The mechanism associated with improvement of soil nutritional status by oilseed rape crop, leading to better performance of rice crop, in rice-oilseed rape cropping systems is little known. The present study was aimed to test the hypothesis that earthworm casts produced during oilseed rape-growing season have positive effects on grain yield and fertilizer nitrogen (N) utilization in the subsequent flooded rice crop. A 15N-tracing pot experiment was conducted to determine the effects of earthworm casts collected from oilseed rape fields on yield attributes in rice and the fate of fertilizer N. Soil treated with earthworm casts (soil: earthworm casts = 4: 1, w/w) (EC1) produced 39% higher grain yield than soil only (EC0). EC1 had 18% more panicle number and 10% higher spikelet filling percentage than EC0. Aboveground biomass and harvest index were higher in EC1 than in EC0 by 20% and 15%, respectively. SPAD values in flag leaves were 10% and 22% higher under EC1 than EC0 at 15 and 20 days after heading, respectively. EC1 had 19% higher total N uptake and 18% higher physiological N-use efficiency than EC0. These positive effects of earthworm casts on yield attributes offset negative effects of decreasing N rate from 0.74 g pot–1 (equivalent to the recommended field rate of 150 kg ha–1) to 0.44 g pot–1 (equivalent to 60% of the recommended rate). Fertilizer N retention rate was 7% higher while fertilizer N loss rate was 6% lower in EC1 than in EC0. Our study suggests that earthworm casts produced during oilseed rape-growing season are expected to have the following benefits on the subsequent flooded rice system: (1) improving growth and physiological processes in rice plants and consequently increasing rice grain yield, and (2) increasing fertilizer N retention rate and hence decreasing fertilizer N loss rate and reducing environmental risk.

Effects of nitrogen fertilization rate on tocopherols, tocotrienols and γ-oryzanol contents and enzymatic antioxidant activities in rice grains

“…Results showed that with the exception of pH, the contents of total nitrogen, Mehlich III P and K, and organic matter in soils were lower at harvesting than before planting (Table 1), and there was no difference in these measurements between nitrogen treated groups and the control. This observation suggests that in addition to have been absorbed by the rice plants, some of the applied nitrogen fertilizers may have lost via denitrification, and hence resulting in a lower total nitrogen concentration after planting (Fillery and Vlek 1982;Huang et al 2016).…”

A Comparison of Nitrogen Transfer and Transformation in Traditional Farming and the Rice–Duck Farming System by 15N Tracer Method

“…Therefore, decreasing inorganic fertilizer use may solve environmental issues. Other studies showed that decreasing N rates from 0.74 g pot −1 (equivalent to the recommended field rate of 150 kg ha −1 ) to 0.44 g pot −1 (equivalent to 60% of the recommended rate) resulted in lower fertilizer N loss rates [27].…”

Experimental warming reduces fertilizer nitrogen use efficiency in a double rice cropping system

“…Calculations and statistical analyses. Plant N uptake derived from fertilizer and soil was calculated as follows (Huang et al 2014(Huang et al , 2016:…”