Read on:

• Feeding a Hungry World
  This editorial from Norman Borlaug who was awarded the Nobel Peace Prize in 1970 was published in Science magazine, 19 October 2007. It starts... "Next week, more than 200 science journals throughout the world will simultaneously publish papers on global poverty and human development - a collaborative effort to increase awareness, interest, and research about these important issues of our time." In this editorial, Dr. Borlaug describes the challenges the world is facing and the role of advanced agriculture in meeting these challenges.
  http://www.sciencemag.org/cgi/content/full/318/5849/359
• The Impact of Agricultural Soil Erosion on the Global Carbon Cycle.
  Van Oost, K., Quine, T.A., Govers, G., De Gryze, S., Six, J., Harden, J.W., Ritchie, J.C., McCarty, G.W., Heckrath, G., Kosmas, C., Giraldez, J.V., Marques, J.R., and R. Merckx. Published in Science, Vol. 318 Issue 5850, pp 626-629.
• Assessing the Impact of the National Agricultural Advisory Services (NAADS) in the Uganda Rural Livelihoods. Benin, S., E. Nkonya, G. Okecho, J. Pender, S. Nahdi, S. Mugarura, E. Kato, and G. Kayobyo. October 2007. IFPRI Discussion Paper 724.
  http://www.ifpri.org/pubs/dp/ifpridp00724.asp.

Increasing Applications of Potassium Fertiliser to Barley Crops Grown on Deficient Sandy Soils Increased Grain Yields while Decreasing some Foliar Diseases

Most sandy soils used for cropping in south-western Australia(SWA) have now become potassium (K) deficient due to removal of K in hay and grain, so it is now profitable to apply K fertiliser to most barley (Hordeum vulgare L.) crops in the region. Leaf diseases of barley crops in the region have increased in recent years particularly in the in medium to high (350-600mm annual average rainfall) areas of SWA. Seventeen field experiments were undertaken to determine the effect of applications of K fertiliser, either the chloride (KCl) or sulfate source (K₂SO₄), on grain yield increases and on the percentage leaf area diseased (%LAD) when diseases were controlled or not controlled by fungicide sprays.
Maximum grain yield of barley was achieved where adequate K fertiliser (~8-22 kg K/ha)was applied and leaf diseases were controlled by fungicide. Applying increasing amounts of applied K fertiliser (0-120 kg K/ha) to barley decreased the %LAD by powdery mildew (Blumeria graminis f. sp. hordei Syn.) and spot-type net blotch (Pyrenophora teres f. maculata (Sacc.) Shoem.) and increased grain yield. By contrast, when leaf rust (Puccinia hordei G. Otth) was present the %LAD was unaffected by K application. When powdery mildew was the major disease, larger increases in grain yields and larger reductions in %LAD were obtained when KCl was used instead of K₂SO₄. About twice as much K fertiliser as K₂SO₄ was required for 90% maximum grain yield compared with KCl where powdery mildew was present. Applying larger amounts (>40 kg K/ha) of K fertiliser than required to achieve maximum grain yields did not further reduce %LAD by powdery mildew. There were no significant differences between the 2 sources of K fertiliser on the %LAD by spot-type net blotch.
Generally, the percentage protein content and hectolitre weight of grain were unaffected by K fertiliser. Potassium fertiliser decreased the percentage grain <2.5mm (known locally as screenings) and control of the foliar leaf diseases by applications of fungicide resulted in a decrease in protein content and screenings and increased hectolitre weight of barley grain.

The concentration of K in dried shoots that was related to 90% of the maximum shoot yield (critical diagnostic K) decreased as the plant matured, and was ~41 g/kg at Z22, ~30 g/kg at Z32, ~20 g/kg at Z40, and ~15 g/kg at Z59. The concentration of K in dried shoots which was related to 90% of the grain yield (critical prognostic K) decreased as plant matured, and was similar to critical diagnostic K values. Leaf disease had little effect on critical concentrations of K at early growth stages (Z22 and Z32).

Performance of Site-Specific Nutrient Management for Irrigated, Transplanted Rice in Northwest India

Like in other parts of Asia, irrigated, transplanted rice (Oryza sativa L.) yield increases in Punjab, India, have slowed down in recent years. Further yield increases are likely to occur in smaller increments through fine-tuning of crop management mainly by accounting for the large spatial and temporal variation in soil characteristics. On-farm experiments were conducted from 2002 to 2004 at 56 sites in six key irrigated rice-wheat (Triticum aestivum L.) domains of Punjab to evaluate an approach for site-specific nutrient management (SSNM). Field-specific NPK applications were calculated by accounting for the indigenous nutrient supply, yield targets, and nutrient demand as a function of the interactions between N, P, and K. The performance of SSNM was tested for two rice crops. Compared with the current farmers' fertilizer practice (FFP), average grain yield increased from 5.1 to 6.0 Mg ha1, while plant N, P, and K accumulations increased by 13 to 15%. The gross return above fertilizer cost (GRF) was about 14% greater with SSNM than with FFP. Improved timing and/or splitting of fertilizer N increased N recovery efficiency from 0.20 kg kg1 in FFP plots to 0.30 kg kg1 in SSNM plots. The agronomic N use efficiency was 83% greater with SSNM than with FFP. The year-wise effect on all parameters was, however, nonsignificant. As defined in our study, SSNM has potential for improving yields and nutrient efficiency in irrigated, transplanted rice.

Categorisation of Soils Based on Potassium Reserves and Production Systems: Implications in K Management

Crop fertilisation with potassium in rainfed agriculture in India is not practised, merely on the assumption that Indian soils are rich in potassium and crops do not need external K supply. However, under continuous cropping in rainfed regions, huge crop K removals are reported, up to 150-200 kg/ha annually, depending upon amount and distribution of rainfall and biomass production. Thus, most of the crops essentially deplete soil K reserves. The present study evaluates the soil K reserves under diverse rainfed production systems and categorises rainfed soils based on different soil K fractions. Depth-wise sampling was done from 21 locations across different soil types under 8 production systems, and various fractions of soil K were determined. Total K was highest in Inceptisols (1.60-2.28%), followed by Aridisols (1.45-1.84%), Vertisols and Vertic sub-groups (0.24-1.72%), and Alfisols and Oxisols (0.30-1.86%), showing a wide variation within each group. Non-exchangeable K reserves were found in a proportionate manner to total K in most of the soil profile. Unlike non-exchangeable K reserves, Vertisols had higher exchangeable K than Inceptisols and Alfisols/Oxisols. Non-exchageable K showed significant positive correlation with total K in Inceptisols and Vertisols, whereas it was non-significant in Alfisols/Oxisosls. However, significant positive correlations were recorded with exchangeable K and non-exchangeable K in all soil types, indicating the dynamic equilibrium between 2 soil K fractions. Non-exchangeable K reserves were included along with exchangeable K in categorising soils into 9 groups for evolving better strategies to manage soil K fertility in rainfed agriculture in India. Finger millet and groundnut crops at Bangalore and Anantapur regions (category I) need immediate attention on K nutrition, as these soils are low in both exchangeable and non-exchangeable K. Similarly, crops grown on soils of S.K. Nagar, Ballowal-Saunkri, and Rakh-Dhiansar, with low exchangeable K and medium non-exchangeable K, would need K fertilisation as these crops (maize and pearl millet) are K-exhaustive (category II). Pearl millet and upland rice in category III and cotton in category IV need K additions at critical stages. Upland rice in category V needs a maintenance dose of K. In category VI, cereal crops may not need K additions immediately as they have medium exchangeable K and high non-exchangeable K. Long-term sorghum cropping may need K supply after few years (category VII). Soils in category VIII are adequate in non-exchangeable K and medium exchangeable K and the crops, groundnut, cotton, sorghum, and soybean, may not need external K immediately. For soils in category IX, K fertilisation is not required to the crops (sorghum and soybean) as these soils have high exchangeable and non-exchangeable K.

Influence of Nitrogen and Potassium Supply on Contents of Acrylamide Precursors in Potato Tubers and on Acrylamide Accumulation in French Fries

Fried potato products may accumulate substantial amounts of acrylamide due to high precursor contents, namely reducing sugars and asparagine. In a two-factorial experiment increasing N supply, increased the contents of reducing sugars in most cases, and resulted in higher contents of free amino acids. α-amino-N, which was tightly correlated with the contents of free amino acids, can be regarded a suitable rapid test for free asparagine for a given variety. Increasing K addition always raised the citrate contents, but lessened the contents of reducing sugars. Selected treatments were processed into French fries. Highest acrylamide contents were observed in tubers grown with high N and inadequate K supply, which also contained the highest contents of precursors. The experiment clearly demonstrates that nutrient supply has significant impact on the contents of acrylamide precursors and thus for the acrylamide formation during frying.

The Long-Term Impact of Phosphorus and Potassium Fertilization on Alfalfa Yield and Yield Components

Addition of P and K fertilizer can increase alfalfa (Medicago sativa L.) yield and stand persistence, but the yield components associated with P- and K-induced variation in agronomic performance are not clear. Our objectives were: (i) to determine the impact of P and K nutrition on productivity of a relatively old alfalfa stand; and (ii) determine which yield components are associated with changes in alfalfa forage yield. Treatments were a factorial combination of four P and five K rates replicated four times. Forage harvests occurred four times annually. Plant populations were determined in early December and late May each year. When compared to unfertilized plots, addition of P and K increased forage yield each year. Fertilization with P decreased plants m2 at all K application rates, but especially in plots fertilized with P, but not K. By comparison, plots fertilized with K, but not fertilized with P, had the higher plant population densities. Although regression analysis eventually revealed a positive association between forage yield and shoots m2 in 2003 and 2004, the greatest forage yields were not obtained in plots with the greatest plant population densities, shoots plant1 or shoots m2. Regression and path analysis revealed that improved forage yield in P- and K-fertilized plots was consistently associated with greater mass shoot1.

Soil and Tissue Phosphorus, Potassium, Calcium, and Sulfur as Affected by Dairy Manure Application in a No-Till Corn, Wheat, and Soybean Rotation

The hypothesis of this study was that surface applied liquid manure may provide sufficient nutrients to silage corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] under a no-till system in the cool wet climate of Atlantic Canada. A 2-yr field study was conducted investigating the effect of crop rotation and fertility on P, K, Ca, and S availability to corn silage, spring milling wheat, and soybean in Nova Scotia, Canada. The rotations consisted of all six possible combinations of corn, wheat, and soybean, and the fertility treatments consisted of three rates of liquid dairy manure (LDM13) at 32.1, 48.1, and 64.3 Mg ha1, a mineral fertilizer treatment, and a control (no fertility applied). In general, nutrient availability as measured by Mehlich 3 (M3) was not well correlated with tissue concentration. Tissue S in corn was lower when it was grown after soybean than when grown after wheat, and was highest in the LDM1 and in the control treatments. Rotation x fertility effects observed in the wheat nutrient removals were accountable to similar differences in yield. Wheat uptake of P was significantly affected by fertility, with the highest removal of P occurring in the NPK treatment, which also provided the highest yield. Results indicate that Ca uptake by wheat may be hindered by competition with K, and that K applied in manure at higher rates could build up over time. Potassium recovery in wheat was higher from the inorganic NPK treatment (37%) than from manure (from 16 to 4%). There were few differences in M3 available nutrients in 2001. However in 2002, LDM application resulted in higher M3 concentrations of K and Ca; there was a drop in P availability with the LDM3 (at 64.3 Mg ha1) application; and S availability was highest at LDM1 and LDM3 (32.1 and 64.3 Mg ha1, respectively). Further long-term studies may be needed to determine if surface applied LDM with no incorporation can sustain silage corn, soybean, and wheat nutrient requirements for P, Ca, K, and S, and maintain efficient nutrient use overtime under no-till conditions.

Nutrient Balance in Rice

Study of nutrient balance in rice helps in optimization of fertiliser application for achieving higher rice productivity and improving soil quality. Imbalanced use of fertilisers has deleterious effect on soil fertility and rice yield in long run. Over a period of 21-23 years, the average response to 30-60 kg K₂O/ha in laterite soil at Bhubaneswar, red loam soil at Hyderabad and Terai soil at Pantnagar varied from 0.4-0.6 t ha. The share of N in total grain yield response to NPK+FYM decreased and that of P and K increased with years of cropping at all locations. In general, with application of N as well as P, there was positive balance of these two nutrients in rice-rice system. But even with application of K fertilisers @ 40-60 kg K₂O/ha, the K balance in rice was negative suggesting the need for adequate supply of K to rice for obtaining sustainable high yield. The sustainable yield index was higher in the integrated use of N, P, K and farmyard manure than N, NP and NPK.

Effect of CO₂ Enrichment on the Growth and Nutrient Uptake of Tomato Seedlings

Exposing tomato seedlings to elevated CO₂ concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO₂ on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO₂ (360 or 720 L L-1) and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age), and the seedling vigor index (seedling vigor index = stem thickness/(plant height x total plant dry weight) increased with the elevated CO₂, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO₂ did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO₂ treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO₂ concentrations.