Read on:

• IWMI Research Report 140: An Assessment of Crop Water Productivity in the Indus and Ganges River Basins: Current Status and Scope for Improvement. Cai et al. 2010. ISBN 978-92-9090-735-0.
• The Economist: Food Prices. 2 June 2011.
• IFA Wiki: Welcome to the Crop Nutrition Wiki.
• The Economist: Hindering Harvests: Changes in the climate are already having an effect on crop yields - but not yet a very big one. 5 May 2011.
• ECOS: Australia's Carbon Farming Initiative: A World First. Michele Sabto, M., and J. Porteous. CSIRO Publishing, 4 May 2011.
• Journal of Functional and Environmental Botany: Nitrogen Assimilation and Yield of Lepidium sativum [L.] As Affected by Potassium Availability. Nidhi Gauba Dhawan, Shahid Umar, Tariq O. Siddiqi and Muhammad Iqbal. Indian Journals.com. 1(1):1-10, 2011.
• Pakistan Journal of Agricultural Sciences: Potassium Application Reduces Bareness in Different Maize Hybrids under Crowding Stress Conditions. M. Ahmad alias Haji A. Bukhsh, Riaz Ahmad, Javaid Iqbal, Safdar Hussain, Atique ur Rehman and M. Ishaque. 48(1):31-38, 2011 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906. http://www.pakjas.com.pk.
• Communications in Biometry and Crop Science: Distribution of ¹⁴C into Biochemical Components of Soybean Exposed to Water Deficit and Potassium. Kamel et al. 5(1):27-33, 2010. International Journal of the Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Poland.
• Nature: Agriculture: Beyond Food versus Fuel. Graham-Rowe, D. 474:6-8, 23 June 2011.
• Nature: Perspective: A New Hope for Africa. Lynd and Woods. 474:20-21, 23 June 2011.

Corn Responses to In-Furrow Phosphorus and Potassium Starter Fertilizer Applications

Starter N-P or N-P-K fertilizers often are applied to corn (Zea mays L.), but questions arise concerning the usefulness of starter K. This study assessed responses of corn grain yield, early growth, and early P and K concentration and uptake to in-furrow fluid P-K and K starter fertilizers. Six replicated small-plot trials evaluated a control receiving no P or K, 3-8-15 (N-P-K) starter at 5 to 7 kg P ha^-1 and 10 to 14 kg K ha^-1, 0-0-25 (N-P-K) starter at 10 to 14 kg K ha^-1; broadcast fertilizer at 49 to 66 kg P ha^-1 and 112 to 140 kg K ha^-1; and broadcast-starter combinations. More N (191-224 kg ha^-1) was applied uniformly. Eight replicated field-length strip-trials evaluated 0-0-25 starter at 10 to 14 kg K ha^-1, broadcast fertilizer at 112 kg K ha^-1, and broadcast plus starter. More N (168-224 kg ha^-1) and P (49-66 kg ha^-1) were applied uniformly. The fields encompassed various tillage systems, hybrids, soils, and soil-test levels. Starter P-K applied in addition to broadcast P-K increased growth and P and K uptake compared with broadcast P-K at two trials, but did not increase yield. Starter K applied in addition to broadcast P-K at the small-plot trials or broadcast K at the strip-trials did not increase growth compared with broadcast fertilization, decreased K uptake at 2 of the 14 trials, and did not affect yield. Potassium seldom had a starter effect on corn. Starter K may not increase corn early growth or yield unless the soil is deficient in K and broadcast K is not applied.

Potassium Fertilization on Maize under Different Production Practices in the North China Plain

Potassium fertilization is uncommon in the North China Plain (NCP), especially in maize (Zea mays L.) production. Our specific objectives in this study were to determine yield response to K fertilization as affected by conventional as well as high-yielding production practices. Seven field experiments were conducted in the NCP. The factorial study compared three levels of K fertilization (K0 = no K; K1 = medium K rate; K2 = high K rate) and two levels of production practices: conventional (CP) and high yielding (HP). At all sites, HP outperformed CP in terms of maize grain yield except at ZD in 2006. On average, maize grain yields were enhanced by 9.9 and 14.9% under CP and 15.7 and 21.0% under HP at the K1 and K2 levels, respectively. Maize yield response, as well as economic profit from applied K, were greater under HP than CP, on average, across seven site-years. Medium K inputs improved partial factor productivity (PFP) of applied N and P, while higher rates had inconsistent results. Overall, PFP and agronomic efficiency of applied K were improved under HP, as was the apparent recovery efficiency of applied K, which suggests positive interactions among K and other high-yielding production practices. Negative K balances were observed in all of the K0 and K1 treatments in both years and under both production practices, especially under HP. In intensive agricultural soils of the NCP with higher K content relative to South China, optimal K fertilization will improve soil fertility and support high grain yield.

Re-Visiting Potassium and Phosphate Fertilizer Responses in Field Experiments and Soil-Test Interpretations by Means of Data Mining

Currently, potassium (K)- and phosphate (P)-fertilizer recommendation in Germany is based on standardized soil-testing procedures, the results of which are interpreted in terms of nutrient availability. Although site-specific soil and plant properties (e.g., clay and carbon content, pH, crop species) influence the relation between soil nutrient content and fertilizer effectiveness, most of these factors are not accounted for quantitatively when assessing fertilizer demand. Recent re-evaluations of field observations suggest that even for soil nutrient contents well within the range considered to indicate P or K deficiency, fertilizer applications often resulted in no yield increase. In this study, results from P- and K-fertilization trials (in total about 9000 experimental harvests) conducted during the past decades in Germany and Austria were re-analyzed using a nonparametric data-mining procedure which consists of a successive segmentation of the data pool in order to elaborate a modified recommendation scheme. In addition to soil nutrient content, fertilizer-application rates, nutrient-use efficiency, and site properties such as pH, clay content, and soil organic matter, have a distinct influence on yield increase compared to an unfertilized control. For K, nutrient-use efficiency had the largest influence, followed by soil-test K content, whereas for P, the influence of soil-test P content was largest, followed by pH and clay content. The results may be used in a novel approach to predict the probability of yield increase for a specified combination of crop species, fertilizer-application rate, and site-specific data.

Nutrient Management Strategies in Rainfed Agriculture: Constraints and Opportunities

Dryland soils are not only thirsty but also hungry. Low productivity from rainfed regions is due to water deficit, recurring droughts, degraded lands (mostly affected due to water erosion causing soil loss up to 16 t ha ^-1 year^-1), poor soil health, water and nutrient stress, multi-nutrient deficiencies, high evaporation rate, low infiltration rate and poor crop management factors. Moisture stress further affects the nutrient availability to the crop since nutrient mobility depends on optimum soil moisture. As top fertile soil layer is eroded in absence of soil cover, low soil organic matter and deficiency of secondary and micronutrient have emerged as important productivity constraints. Therefore, improving nutrient and water use efficiency is crucial for sustainability of rainfed production systems. Hence concerted efforts are needed to develop soil and crop management factors to mitigate the water and nutrient stress to maximize food production with minimum environmental degradation. Potential yield increase in rainfed agriculture, soil fertility issues, importance of soil health and on farm demonstration of livelihood impacts of balanced and integrated nutrient management and strategies for improving nutrient use efficiency are discussed in the paper.

Fertiliser Response and Nutrient Management Strategies for Cotton

Soil related constraints, notably fertility, are a major impediment in realizing potential cotton yields. Insufficient nutrient additions compared to nutrient uptake leads to a decline in soil fertility. Across cotton growing regions, nutrient balance was negative except for P. To mitigate nutrient stress and improve productivity, a balanced nutrient management plan is the only option. This paper presents the nutrient response to fertilisers of the conventional non-Bt and the recently introduced Bt transgenics. Recommendations pertaining to site-specific nutrient management and integrated nutrient management are also discussed.

Nutrient Management Strategies in Tropical Tuber Crops

Tropical tuber crops are the primary staple food of the wet tropics and in India these crops are cultivated as a secondary staple as well as for many commercial applications such as production of starch and sago. These crops are adapted to low fertility tropical soils with high acidity and low inherent nutrients levels. Cassava, sweet potato, yams and aroids are the important ones in this group and all these crops respond well to application of manures and fertilisers. During the past 45 years, a lot of research studies have been done to develop different nutrient management strategies for these crops. The nutrient removal, nutrient deficiency symptoms, index tissues for plant analysis and critical nutrient concentrations were identified for nutrient management. Initially the yield of these crops could be substantially increased by developing blanket fertiliser recommendations. Later on, soil test based fertiliser recommendations for targeted yields were conducted to develop target yield equations and these equations were developed for cassava and sweet potato only, that too for limited regions. Later on, site-specific nutrient management (SSNM) technology has been developed for cassava and effectively implemented in farmers' fields for field scale nutrient recommendations in major cassava growing regions. Under the SSNM technology, spatial and temporal variability of soil and canopy properties are considered using tools such as simulation models, leaf colour charts and chlorophyll meter for making variable rate fertiliser recommendations. Development of SSNM technology in other tropical tuber crops is also being envisaged.