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Relation Between Soil Organic Matter and Yield Levels of Nonlegume Crops in Organic and Conventional Farming Systems

The aim of this study was to evaluate the interaction between yield levels of nonleguminous crops and soil organic matter (SOM) under the specific conditions of organic and conventional farming, respectively, and to identify implications for SOM management in arable farming considering the farming system (organic vs. conventional). For that purpose, correlations between yield levels of nonlegume crops and actual SOM level (Corg, Nt, Chwe, Nhwe) as well as SOM-level development were examined including primary data from selected treatments of seven long-term field experiments in Germany and Switzerland. Yield levels of nonlegume crops were positively correlated with SOM levels, but the correlation was significant only under conditions of organic farming, and not with conventional farming treatments.

While absolute SOM levels had a positive impact on yield levels of nonlegumes, the yield levels of nonlegumes and SOM-level development over time correlated negatively. Due to an increased demand of N from SOM mineralization, higher yield levels of nonlegumes obviously indicate an increased demand for OM supply to maintain SOM levels. Since this observation is highly significant for farming without mineral-N fertilization but not for farming with such fertilization, we conclude that the demand of SOM-level maintenance or enhancement and thus adequate SOM management is highly relevant for crop production in organic farming both from an agronomical and ecological point of view. Under conventional management, the agronomic relevance of SOM with regard to nutrient supply is much lower than under organic management. However, it has to be considered that we excluded other possible benefits of SOM in our survey that may be highly relevant for conventional farming as well.

Progress in Significant Soil Science Fields of China over the Last Three Decades: A Review

Due to continuous decreases in arable land area and continuous population increases, Chinese soil scientists face great challenges in meeting food demands, mitigating adverse environmental impacts, and sustaining or enhancing soil productivity under intensive agriculture. With the aim of promoting the application of soil science knowledge, this paper reviews the achievements of Chinese scientists in soil resource use and management, soil fertility, global change mitigation and soil biology over the last 30 years. During this period, soil resource science has provided essential support for the use and exploitation of Chinese soil resources, and has itself developed through introduction of new theories such as Soil Taxonomy and new technologies such as remote sensing. Soil fertility science has contributed to the alleviation and elimination of impeding physical and chemical factors that constrain availability of essential nutrients and water in soils, the understanding of nutrient cycling in agroecosystems, and the increase in nutrient use efficiency for sustainable crop production. Chinese soil scientist have contributed to the understanding of the cropland's role in global change, particularly to the understanding of methane and nitrous oxide emission from rice fields and the effect of elevated carbon dioxide and ozone on rice-wheat system. Soil biology research has progressed in biological N fixation, distribution of fauna in Chinese soils, and bioremediation of polluted soils. A new generation of soil scientists has arisen in the last three decades. The gaps between research and application in these soil science fields are also discussed.

Effect of Long-Term Potassium Fertilization on Crop Yield and Potassium Efficiency and Balance Under Wheat-Maize Rotation in China

Sustainable potassium (K) management at different soil sites requires understanding the relationships between crop productivity and long-term K fertilizations on a regional or national scale. We analyzed responses of grain yield of wheat (Triticum aestivum L.) and maize (Zea mays L.), K efficiency, and partial balance (difference between K input through fertilizer and K output in the aboveground biomass) during 15- (1990-2005) or 18-year (1990-2008) K fertilizations at five distinctive agroecological zones across China. Compared to the inorganic nitrogen (N) and phosphorus (P) fertilization, the inorganic NPK fertilization significantly increased grain yields of wheat (21%) and maize (16%-72%) at Qiyang and Changping, where soils have low exchangeable and non-exchangeable K contents, but not at Ürümqi, Yangling and Zhengzhou, where soils have a high exchangeable and non-exchangeable K and/or low N/K ratio in crop plants. Compared to the inorganic NPK fertilization, the inorganic NPK (30% N) and organic manure (70% N) fertilization (NPKM) increased grain yields of wheat (14%-40%) and maize (9%-61%) at four sites, but not at Zhengzhou. For a productivity of wheat at 2-5 t ha-1 or maize at 3-6 t ha-1, 13-26 or 9-17 kg K ha-1 were required to produce 1.0 t wheat or maize. The NP fertilization resulted in the lowest negative partial K balance and accumulated 52 kg K ha-1 year-1 less than the NPK fertilization, which accumulated 28 kg ha-1 year-1 less K than the NPKM fertilization. A re-evaluation of the site-specific fertilization effects on N/K ratio in crop plants and soil K accumulation under current NPK and NPKM fertilization is urgently needed to increase both crop yield and K use efficiency at different agroecological zones across China.

Effects of K and N Nutrition on Function and Production of Ranunculus asiaticus

Potassium (K) affects a range of physiological processes in the plant and is a key factor controlling crop productivity and yield quality. Little information is available concerning effects of K nutrition on function of cut flower plants. The present study was carried out to investigate the interaction between K and N nutrition, on flower quantity and quality of Ranunculus asiaticus L. The plants were supplied with three levels of K fertigation (60, 120, or 180 mg K L-1) under 50 mg N L-1 application, and at the intermediate level of 120 mg K L-1, to three levels of N applications (50, 100, or 150 mg N L-1). The two lowest K treatments and the lowest N treatment excelled in flower production due to the lower incidence of stem-toppling, a disorder associated with localized Ca deficiencies in rapidly expanding tissues of the flower stem. Detrimental effects in terms of yield quality were apparent already under supply of 180 mg K L-1 and 50 mg N L-1, and were not associated with changes in osmotic potential, relative water content or membrane stability of the plant tissue, or with changes in mineral contents of the leaves other than reduced Ca under high N application. Our results suggest a low nutritional requirement of R. asiaticus L. for K and N, a lack of involvement of tissue water relations in the reduced flower quality under the application of high concentrations of K and N, and an induction of stem toppling under high application of N and K by reduced availability of Ca to the expanding tissue of the flower stem.

Simultaneous Extraction of Phosphorus, Potassium, Calcium and Magnesium from Soils and Potassium Recommendations for Crops in Southern Brazil

Simultaneous multi-element extraction has been increasing worldwide to improve soil laboratory testing quality and efficiency. This study sought to investigate the applicability of the Mehlich-1, Mehlich-3 and resin methods for simultaneous extraction of soil available P, K. Ca, and Mg as well as the effect of using conversion equations on nutrient recommendations for crops. Topsoil (0-20 cm) samples were taken from the most representative soil types used for crop production in southern Brazil with a wide range of chemical, physical, and mineralogical properties. Soil P, K, Ca, and Mg were simultaneously extracted using 1.0 mol L-1 KCl, Mehlich-1 and Mehlich-3 solutions, and membrane resin. The amounts of P extracted with the Mehlich-1 method were, on average, 50% lower than those extracted with the resin and Mehlich-3 methods. However the resin method extracted the lowest amounts of K, Ca, and Mg. The use of conversion equations was suitable and it did not affect negatively the K recommendations for crops grown on soils of southern Brazil.

Nutrient Use Pattern in Rice under Irrigated Agro-ecosystem of Haryana

A comprehensive survey was undertaken in potential rice growing district Kurukshetra (Haryana) during 2008 to assess the varietals distribution and nutrient use pattern in rice. The study revealed that 60% farmers grew basmati rice in 57% of total area under rice and rest of the farmers cultivated coarse rice including dwarf hybrids. The productivity of dwarf varieties remained higher than hybrids. Due to higher productivity, 42% farmers preferred evolved basmati including non-descript varieties in comparison to traditional scented basmati in spite of its higher market price. About 20-22% farmers used under dose (86-115 kg N/ha) of N-nutrient in 19-25% area whereas, more farmers (25-43%) applied excess dose (172.5 kg N/ha) of N-nutrient in larger area (22-48%) without substantial gain in productivity of dwarf rice. Contrary to N use pattern, 32-43% farmers used half of recommended dose of P-nutrient in about 25-27% area and 57-68% farmers used right dose (57.5 kg P2O5/ha) of P-nutrient in 51-64% area under dwarf rice. Majority of farmers did not use K-fertilisers, though the response to 37.5 kg K2O/ha were observed in dwarf and basmati rice. Maximum number of farmers (81-84%) applied recom-mended dose (25 kg ZnSO4/ha) of zinc sulphate in dwarf and basmati rice. Similar to dwarf rice, 42-56% farmers used excess dose of N-fertilisers resulting in yield loss in basmati rice. About 35-69% farmers applied double dose of P-nutrient.

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September 2011

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