Nitrogen Cycling with Respect to Environmental Load in Farm Systems in Southwest China

Abstract

In Qibainong, a steep-mountainous karst region in southwestern China, self-sustaining societies have long existed, but increasing socioeconomic liberation has fuelled the recent rapid structural change of its economy. Consequently, environmental deterioration and exhaustion of resources have become problematic issues. We carried out a field survey in Qibainong in southwestern China and used both estimated and measured N flows and N balances from obtained results. Our results are summarized as follows (1) farmers used large amounts of chemical N fertilizers at intensities of 113-1124 kg N ha À1 ; (2) substantial application of chemical fertilizer in Qibainong has contributed to an increase in potential NO 3 -N leaching of 6-511 kg N ha À1 , followed by NH 3 volatilization; (3) crop products are largely distributed to feed livestock, the products of which are a major income source; (4) this area has a great requirement for imported food; (5) in addition, unused manure N (up to 191 kg N ha À1 ) is generated by the increase in manure N production. Chemical fertilizer application, in addition to unused manure can be regarded as a major source of environmental damage. Based on the relationship between the N application rate and the NO 3 -N leaching potential, we estimated the critical limit of the N application rate of chemical fertilizer + manure to be 297 kg N ha À1 . In Qibainong, unused manure, which is an important nutrient resource, was applicable within the critical limit. We recommend that all manure N produced within the village be used effectively on arable land, and that any shortages be supplemented by chemical N fertilizer up to 297 kg N ha À1 to maintain water resource quality. Further improvement might be achieved through incorporating chemical fertilizers, P and K supplemented manure, and so on.

Nitrogen loss from karst area in China in recent 50 years: An in‐situ simulated rainfall experiment's assessment

“…On the other hand, widespread use of N‐based chemical fertilizers (averaging 113–1,124 kg Nha −1 ) may greatly aggravate the dangerous of agricultural nonpoint N pollution (Liang et al., ). As karst aquifers are particularly vulnerable to contamination, the fertilizers will be a potential source of pollution especially at unconfined karst zone (Różkowski and Różkowski, ).…”

“…Thus, the Chinese Government's current 5‐year plan has set a stringent target “Zero Increase Action Plan” for fertilizers by 2020. Leaching of soluble N species (mainly nitrate; NO 3 − ) from the thin, calcareous soils of karst systems may reduce the ability of the soil to provide vital ecosystem services, for example, nutrients and water regulation and supply, carbon sequestration, and food production (Zhang et al, 2011a, 2011b; Huebsch et al., ; Liang et al, ; Zhu et al., ). Therefore, a fuller understanding of the controls on erosional processes and the correlation between water and N cycle in karst topographies is imperative in terms of long‐term soil and water security in these fragile regions.…”

Effects of different organic materials on forage yield and quality of silage maize (Zea mays L.)

“…On the plots where PL and CM were applied to meet N requirements, crop N requirement (300 kg ha -1 ) and N content of the litter or manure were considered. Soil N content was not taken into account because only 1%-2% of total N content of soil is in a readily available form to plants; therefore, it is not reliable data for fertilization recommendations (Liu et al, 2003;Liang et al, 2005;Bao et al, 2006). Treatments were applied on the same plots in the second year of the experiment and this led to some differences in the application amounts of the organic materials.…”

Assessment of Nitrogen Pollution Load Potential for Groundwater by Mass Balance in the Tedori River Alluvial Fan Areas, Japan

“…Many studies of the groundwater pollution and the nitrogen cycle have been conducted; for example, a nitrogen budget for late successional hillslope tabonuco forest (Chestnut et al, 2005), groundwater contamination by nitrate (Tsioumas et al, 2011), strategies to reduce nitrate leaching into groundwater (Shrestha et al, 2010), impact of population, food preference and agricultural practice (Xiong et al, 2007), prediction of agriculture derived ground water nitrate distribution (Wang et al, 2006), nitrogen cycling with environmental load in farm system (Liang et al, 2005), distribution of nitrate in groundwater affected by aquitard (Nishikiori et al, 2012), new conceptual model of nitrogen saturation on an oak forest (Lovett et al, 2011), cyclic irrigation of paddy fields at Kasumigaura Lake (Kitamura et al, 2010;Kubota et al, 1979;2000) and at Biwa Lake in the Shiga Prefecture (Hama et al, 2011).…”