K in the Literature

Exploring Remotely Sensed Technologies for Monitoring Wheat Potassium and Phosphorus Using Field Spectroscopy

Given the importance of potassium (K) and phosphorus (P) contents to wheat yield and grain quality, and the very little experience that has been gained on nutritional monitoring of other than nitrogen using remotely sensed technologies, as study was undertaken to explore the possibility of identifying these mineral stresses using spectral data. Canopy spectra and biophysical data were collected from commercial and experimental fields in India and Israel. Traditional and newly developed vegetation indices, together with Partial Leas Squares (PLS) regression models, were calculated in order to predict potassium and phosphorus contents from the wheat canopy spectral data. Results show that the application of PLS and specific narrow bands vegetation indices reached significant levels of accuracy in the retrieval of K and P levels, in comparison to traditional broad band indices. Additionally, it was observed that a significant improvement is obtained when the mineral total content is considered instead of the relative content. Therefore it was suggested that the biomass should also be retrieved from the spectral data. Finally, as very different crop conditions were included in this study, it was possible to confirm that the level of accuracy in the retrieval of K and P levels is related to the quality and variability of the data used for calibrating the models.

Improving Water Productivity by Potassium Application in Various Rice Genotypes

This field experiment evaluated the performance of different rice genotypes under lowland and upland irrigation systems with and without potassium fertilization. The most popular six rice genotypes grown in China; two Indica hybrids viz. Liangyoupei 9 and Xieyou 9308, and four Japonica rice varieties viz. Bing 0001, Bing 0004, Bing 9904 and Huayu # 1 were used in this study. Impacts of two potassium (K) levels (0 & 180 kg ha^-1) and two irrigation systems (lowland & upland) were investigated for yield attributes, grain yield and K uptake of these genotypes. Potassium fertilizer increased the yield of rice, but the response of different genotypes was variable. Effect of upland system on rice yield was diverse with K levels and rice genotypes, whereas K uptake by rice grains was significantly lower than in lowland. Genotypes showed statistical variation for production in both irrigation systems and response to K fertilization. Two genotypes (Liangyoupei 9 & Huayu # 1) performed equally well in both lowland and upland system, as well as with and without K fertilizer. With respect to growth, and yield of rice, generally the lowland system proved superior to upland, and K fertilization helped enhance the crop performance in upland irrigation system. However, upland rice cropping practiced with K fertilization improved water use efficiency of the most genotypes.

Analytical Studies of the CO₂ Soil Test for P and K Fertilization

Extraction of soils with CO₂-saturated water is one of the Swiss reference methods for phosphorus and potassium fertilizer recommendations. Laboratory experiments show that a significant role is played by interactions between CO₂, calcium, phosphate, the only slightly soluble calcium phosphates and lime. Since soil air exhibits increased CO₂ content, these solution equilibria also influence the immediate plant-availability of P in the field. If a soil sample is extracted repeatedly with CO₂ water, the extract will always contain similar P concentrations. This reflects the conditions in the field: a soil can supply plants with P over a fairly long period, even if it periodically dries out or becomes waterlogged. The homeostasis of soils as shown in the CO₂ method explains why it takes years of over- or underfertilization for the P supply of the plants to be affected. CO₂-K also decreases only gradually during sequential extractions. Consequently, the CO₂ method yields a good approximation of the readily plant-available P and K. Although reproducible, the results of the sequential extractions with ammonium-acetate and EDTA (<<AAE10>>) are so different from soil to soil that no direct connection with plant availability can be deduced from a chemical perspective.

Soil Fertility and Crop Productivity: Medium-Term Effect of Organic Inputs and Simplified Cultivation Techniques

The combined effects of the nature of fertilizers (NPK, manure + NPK and liquid manure + NPK), fractionation of the manure inputs (every year or every three years) and tillage (plowing and reduced-tillage) associated with two nitrogen rates (100 or 60% of the optimal dose) on soil fertility and dry matter production of different crops have been studied from 1997 to 2009 in Changins. After twelve years of trial, different soil analyses show that nitrogen fertilization had no effect on soil fertility, only the soil organic matter and total nitrogen contents differed significantly between treatments. In terms of non-limiting nitrogen fertilization, crops treated with manure produced significantly more dry matter than those treated with only inorganic fertilizer. A sub-fertilization with only 60% of the nitrogen fertilizers needs causes a decrease in production of 7-13% according to the treatments. In the absence of the manure input, reducing tillage keeps the stock of soil organic matter, but should be accompanied by a strengthening of nitrogen fertilization. Split manure in annually low inputs doesn

Agroforestry in Switzerland

Trees in agricultural landscapes provide important benefits for the environment. Nevertheless, they are disappearing from cultivated land due to economic and operational reasons. In modern agroforestry systems, trees are planted in rows on agricultural land in order to facilitate mechanical operations. The economic and ecological potential of modern agroforestry systems in Switzerland was examined. Productivity per hectare, profitability and environmental benefits were estimated using computer-aided models. The results show an up to 30% higher productivity (per unit area) of agroforestry systems compared to monocultures. In the long term, agroforestry systems can become profitable. On fertile arable land, they may reduce soil erosion by 78% and nitrate leaching by 46% as well as sequester up to 133 tons of carbon in 60 years. In interviews, farmers were questioned about their perception of benefits and disadvantages of agroforestry. Farmers rate agroforestry systems as non-productive and unprofitable. However, they admit a benefit for biodiversity and cultural landscape. Farmers need to be made aware of the many agroforestry designs and their economic potential, based on the experience of pioneer farmers.