Factors controlling regional grain yield in China over the last 20 years

International audienceFood production is highly dependent on regional yields of crops. Regional differences in grain yields could be due to fertilizer management and climate variability. Here, we analyze trends of grain yields in North China, Northeast China, East China, and Central and Southwest China from 1992 to 2012, using the Chinese statistical yearbooks. We estimate the major factors influencing yield by regression analysis. Results show that fertilizer indices were 40 % for Northeast China, 36 % for East China, 9 % for North China, and 6.8 % for Central and Southwest China. Soil indices were 67 % for Northeast China, 14 % for East China, 90 % for North China, and 6 % for Central and Southwest China. The indices of annual mean temperature were positive for Central and Southwest China (72 %) and East China (39 %), but negative for Northeast China (−15 %) and North China (−16 %). Soil factors explained 80 % of yield variation in North China. Annual mean temperature explained 80 % of yield variation in Central and Southwest China

Changes in regional grain yield responses to chemical fertilizer use in china over the last 20 years

A major challenge facing China is to meet the increasing food demand of its growing population in the face of decreasing arable land area, while sustaining or improving soil productivity and avoiding adverse environmental impacts from intensive agriculture. This study uses data from China Statistical Yearbooks to analyze trends in regional soil productivity and grain yields in the major grain-producing regions in North China (NC), Northeast China (NE), East China (EC), Central China (CC), and Southwest China (SW), associated with regional fertilizer use and annual climate variation in rainfall and mean temperature over the 20 years. During 1992-2012, the average fertilizer increase rates (in kg ha-1 year-1) were in the order of regions CC (6.6) > NC (4.8) > EC (2.4) > SW (2.1) > NE (1.3), while yield responses to fertilizer use (with regression model coefficients, in kg kg-1) were in the order: SW (-0.9) < CC (1.1) < NC (1.7) < EC (5.7) < NE (9.3), showing higher yield responses to fertilizer use for NE and EC than for other regions. The changes in regional grain yields also showed higher yield responses to soil-based productivity for NC, CC, and SW, or to annual climate variability for CC than for other regions, indicating that other factors (such as inherent soil productivity or annual climate variability could be more important than fertilizer in affecting yields. The strategies for regulating nutrient management are needed considerably based on regional indigenous soil nutrient supply under varying regional climate conditions.</p

Balanced N and C input recommendations for rain-fed maize production in northern China based on N balances and grain yields

BACKGROUND: This study aimed to assess longer-term (1993-2009) effects of combined applications of fertiliser, maize stover, and cattle manure on maize yields, partial nitrogen (N) and carbon (C) balances, and water and N-use efficiencies, to guide N and C input recommendations for rain-fed maize production in northern China. RESULTS: The field trial, with three factors at five levels and 12 treatments, was conducted at Shouyang Dryland-Farming Experimental Station, Shanxi, China. Data analysis revealed higher N balances but lower C balances significantly occurred in a dry year than in a wet year. Positive N balances related to higher N inputs resulted in higher soil available N, even downward to deep layers with increasing N inputs, while positive C balances due to higher C inputs could be benefit to increase soil organic C. Based on partial N balances and grain yields, N and C inputs at ranges of 100kg N ha-1 and 1.9-2.9Mg C ha-1 could be recommended for target yields of 6.7-7.2Mg ha-1 in rain-fed maize production. CONCLUSION: The study suggests that N balances close to neutral be given priority to improving N-use efficiency, and more positive C balances also be important for sustaining target yields and soil fertility levels

Soil hydrology for ecohydrology in drylands: examples from Tunisia, China and Cape Verde Islands: a review

A fundamental factor for developing and maintaining the susceptibility of dryland ecosystems is the efficient use of available water. Because of pressure on fresh water resources, practical tools are needed for using more efficiently the rain water, this by regulating soil hydrological processes. For this purpose, 'water harvesting' techniques, referring to small hydraulic structures to collect runoff water, are widely used in arid and semi-arid regions. This paper evaluates three such structures. In Tunisia the indigenous 'jessour' terraces and ground water recharge systems are described. It was found that the CCR (catchment to cropping area ratio) should be larger than 7.4 in order to provide sufficient amounts of runoff water to the terrace for the cultivation of olive trees for an 'average' annual rainfall amount of 235 mm. In China a field experiment was set up in the semi-arid region of the loess plateau to evaluate different tillage practices on their effect on increasing the water storage in the soil profile for better crop growth. It was concluded that subsoiling was the best practice in terms of water conservation. It resulted in the highest increase in water storage during the fallow period, and hence more water was made available to winter wheat during the growing season. On the Cape Verde Islands, with low annual rainfall (100-500 mm), mainly occurring during a few major rainfall events, three land use systems were compared in three adjacent small catchments. A catchment with traditional agriculture and one with natural vegetation, both without soil and water conservation systems, were compared with a catchment with trees in water collecting bench terraces and microcatchments. Lower runoff amounts measured during the third year of monitoring reflected the newly installed soil and water conservation practices in the afforested watershed

Effects of different soil management practices on winter wheat yield and N losses on a dryland loess soil in China

One of the most important problems in the Loess Plateau of China affecting sustainable agriculture is inefficient nutrient use. Field experiments were conducted to study the effects of different soil management practices on the nitrogen (N) dynamics and winter wheat yield on a loess soil in Luoyang, Henan province, China. The results showed that subsoiling with mulch (SS) consistently increased the yield of winter wheat primarily by better water harvest compared with conventional tillage (CT). The influence on yield of no till with mulch (NT) depended on the amount of precipitation. TC (2 crops per year) lowered the winter wheat yield mainly due to the unfavourable soil moisture conditions after growing peanut in summer; however, the harvested peanut gained an extra profit for the local farmer. N uptake by grain and straw and N export was highest for SS. Changes in frequency and intensity of tillage practice altered soil total N content and its distribution along the slope. SS and NT increased the N content of the surface layer (0–0.20 m) compared with CT, but there was no significant effect in deeper soil layers. Considerable amounts of nitrate-N were left in the profile 0–1.60 cm just after harvest under all treatments. The cumulative nitrate-N content to a depth of 1.60m on average was 282 kg/ha, of which 56 kg/ha was in the layer 1.20–1.60 m, which is an indication of considerable nitrate leaching. From data of 7 consecutive years between 1999 and 2006, it could be concluded that SS resulted in the highest yield and total N content in the surface layer, and is the most sustainable tillage option for the circumstances of the study area

Effect of different tillage systems on aggregate structure and inner distribution of organic carbon

Tillage is a common agricultural practice affecting soil structure and biogeochemistry. Pore network geometries are crucial to oxygen concentration, gas diffusivity, water location and water movement. Soil aggregates, 4–6 mm in diameter and collected from silty loam in Belgium and sandy loam in China, were scanned using a micro-computed tomography scanner. Images with a pixel size of 6.9 μm were then processed with ImageJ software for pore network analysis. The treatments were no tillage (C-NT) and conventional tillage (C-CT) in China, and shallow tillage (G-ST) and conventional tillage (G-CT) in Belgium. The results showed that aggregates in conservational tillage (G-ST and C-NT) had numerous connected pores compared with conventional tillage (G-CT and C-CT). The Euler number (Ev) was significantly lower and visible total porosity and surface area (SA) were significantly higher in conservational tillage (G-ST and C-NT) than in conventional tillage (G-CT and C-CT) in both studied locations. The predominant size of pores was significantly higher in conservational tillage (G-ST and C-NT) than in conventional tillage (G-CT and C-CT) (> 150 μm vs 90–120 μm). Pore location within the aggregates also showed differences, with porosity being evenly distributed in the aggregates under conventional tillage (G-CT and C-CT). Under conservational tillage (G-ST and C-NT), the aggregates were heterogeneous, showing higher porosity at the center of the aggregates. There was a higher soil organic carbon (SOC) content in the external layer than in the internal layer in conservational tillage in Belgium (G-ST). In no tillage in China (C-NT), the SOC in the external and internal layers, however, showed similar results. Overall, conventional tillage (G-CT and C-CT) reduced the proportion of the largest pores within soil aggregates, whereas there was no significant relationship between pore morphologies and SOC content. Further investigation is required to measure the active and slow carbon pool distribution in the different layers and under different tillage practices

Soil wet aggregate distribution and pore size distribution under different tillage systems after 16 years in the Loess Plateau of China

In the Loess Plateau of China, conventional tillage is defined as the tillage without crop residues left on the soil surface and ploughed twice a year. The use of alternative practices is a way to reduce soil erosion. Our objectives were to assess the long-term impacts of different soil tillage systems on soil physical and hydraulic characteristics, emphasizing management practices to improve the soil physical qualities (reduce bulk density and increase stability of aggregate) under the conservation tillage system in the Loess Plateau of China. Conventional tillage (CT), no tillage (NT), and sub-soiling (SS) were applied in this experiment. Soil wet aggregates distribution and stability, soil organic carbon (SOC) content, soil water retention curves and pore size distributions were measured. The results showed that in the 0–10 cm and 10–20 cm depth soil layers, NT and SS treatments showed a significantly higher proportion of wet aggregates>250 μm (macroaggregates) compared to CT. In these two layers, the proportion of wet aggregates<53 μm (microaggregates) was significantly higher in CT with respect to NT and SS. SOC content increased as the aggregate fraction size increased, and was higher within wet aggregates>250 μm than within the 250–53 μm and < 53 μm (silt+clay) fractions at both depths. In addition, the conservation tillage (NT and SS) can result in improved total porosity and reduced soil bulk density compared with CT in the surface layer. Pore size distribution in CT soil was unimodal, with the maximum in the 10–30 μm matrix pores of the surface layer. However, in the surface layer the pore size distributions from NT and SS showed a dual porosity curve, with two peaks in the matrix and structural pore areas. The 10–20 cm layer showed similar pore size distributions in each treatment. After scanning the soils by micro-computed tomography, we visualized the pore characteristics. The images showed that CT reduced the long and connected macropores compared with conservation tillage. Overall, soil aggregate stability and soil macropores are most improved under conservation tillage. Conservation tillage with crop residues should be adopted instead of conventional tillage, as an effort to improve crop yield and control soil erosion in the Loess Plateau of China