Soil fertility requires nutrients to exist not only in sufficient quantities but also in balanced form. Balancing soils and achieving optimal soil nutrition will create more favourable soil conditions for better utilization of applied fertilizers and for a greater effect from organic/microbial-based products. Too much of one nutrient may lock up or interfere with the absorption of another.
The soils of the rainfed regions are not only thirsty but are also hungry. Soil erosion with depletion of nutrients under continuous cropping without adequate additions of nutrients and organic matter over the years has resulted in the degradation of soils and its fertility. Wide-spread deficiencies of macro, micro and secondary nutrients have been reported in the rainfed areas (Srinivasarao et al. 2008), and these must be overcome through balanced nutrition of crops.
While much attention has been paid to correcting S and micronutrient deficiencies in irrigated systems, little efforts are made to diagnose secondary and micronutrients deficiencies in the rainfed regions of India. Participatory soil sampling and testing in rainfed regions will, therefore, be a key step in administering balanced nutrition for soil health management.
SSNM nutrient deficiency symptoms Soils of Nalgonda are slightly acidic to alkaline. Among major nutrients, N and P deficiency are very common to the extent of 76 and 29% respectively. Sulphur, B and Zn deficiencies are to the extent of 61 and 51%, respectively, and Fe and Zn deficiencies were observed in 4% and 9% fields respectively.
General description of the study All the crops grown in the cluster is associated with nutrient deficiencies both macro and micro. For optimal crop yield, producers need to recognize the symptoms of nutrient deficiency, the lack of plant available nutrients or nutrient toxicity and excess nutrient uptake. Crops are affected by immediate factors such as weather conditions or injury, excess fertilizer, pesticide drift or insect infestations which may appear to be nutrient deficiencies. It is critical therefore to perform regular soil testing to determine nutrient levels and monitor changes in soil nutrient status. The deficiency symptoms of N, P, K, S, Zn, Fe, and B for major crops grown in Dupahad cluster are discussed below.
The most common visual symptom of nitrogen deficiency is poor plant growth. Leaves become pale green or yellow because they are unable to make sufficient chlorophyll. Leaves in this state are said to be chlorotic. Lower leaves (older leaves) show symptoms first since the plant will move nitrogen from older tissues to more important younger ones. Nitrogen content was low in all of the farmer’s fields in Dupahad cluster. Most of the rainfed crops grown in Dupahad cluster, on average remove 80 to 100 kg N ha-1. Details of nutrient deficiencies in individual farmer’s fields in this cluster indicated severe nitrogen deficiency in soils and were clearly visible in the plants
Symptoms include poor growth, and leaves that turn blue/green but not yellow, oldest leaves are affected first. Undersides of tomato plant leaves, and the veins and stems may turn purple. In general black soils are highly deficient in P. However, in red soils, due to high P applications and less P fixation soil P build-up has increased. In individual farmer’s fields of Dupahad cluster, some of the fields showed available P status as high as 80 kg ha-1. The status of P in soils of this cluster can be classified as low to medium, and crops like maize do show P deficiency
Typical symptoms of potassium deficiency in plants include brown scorching and curling of leaf tips as well as chlorosis (yellowing) between leaf veins. Purple spots may also appear on the leaf undersides. Plant growth, root development, and seed and fruit development are usually reduced in potassium-deficient plants. Often, potassium deficiency symptoms first appear on older (lower)
Whenever the S status of growing plants drops below the critical level required, visual symptoms of S deficiency start appearing on the plant. Sulphur deficiency symptoms in many ways resemble those of N – that is, the leaves become pale-yellow or light-green. Unlike N, S-deficiency symptoms appear first on the younger leaves and persist even after N application. Plants deficient in S are small and spindly with short and slender stalks, their growth is retarded, maturity in cereals is delayed, nodulation in legumes may be poor and N-fixation reduced, fruits often do not mature fully and remain light-green in colour, forages contain undesirably wide N:S ratio and thus have lower nutritive value.
The S content of Dupahad cluster ranged from low to high, however S deficiency was widespread in this cluster with 30 per cent of farmer’s field’s deficit in S. Calcium (Ca) Calcium deficiency symptoms appear initially as localized tissue necrosis leading to stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips. In Dupahad cluster tomato crop was affected by a calcium deficiency in soils Symptoms start as sunken, dry decaying areas at the bottom end of the fruit, furthest away from the stem, not all fruit on a truss is necessarily affected.
In a mild deficiency, pale green stripes appear on either side of the mid-rib of young leaf blades On middle-aged leaves, these stripes become necrotic and the colour of the central leaf changes to a muddy grey-green. In severe deficiencies, leaves turn yellow and the plants are stunted. Dead patches on the leaf cause it to bend or collapse. Both mild and severe zinc deficiencies will reduce grain yield. The Zn content of Dupahad cluster was high in the majority of farmer’s fields, however, Zn deficiency was seen in one or two villages where citrus crops were grown.
The symptoms of iron deficiency appear on the youngest, newest leaves. The area between the leaf veins becomes pale yellow or white (this is called interveinal chlorosis). Usually, no noticeable physical deformity occurs, but in severe cases, the youngest leaves may be entirely white and stunted. It may be difficult to distinguish iron deficiency symptoms from those of other nutrients, particularly zinc, which has similar symptoms in many plants. In iron deficient leaves, interveinal chlorotic lesions are angular and outlined by the leaf veins, whereas the chlorotic lesions in zinc-deficient leaves are more rounded and the edges less sharp.
In Dupahad cluster Fe deficiency was sufficient in most of the villages except in 2 villages where it was deficient and sufficient. For instance, deficiency and sufficiency ranges of Fe in some villages of Dupahad cluster indicated that Fe concentrations below 66 mg kg-1 were Fe deficient, and above were sufficient. Citrus crops grown in this cluster showed Fe deficiency.
The symptoms of boron deficiency reflect the several functions boron fulfils in the plant, but symptoms differ greatly among plant species. The symptoms can often be confused with other deficiencies or disorders (such as virus disease, frost or hormone damage) that cause distorted growth. They also vary depending on the severity of the deficiency. Boron does not easily move around the plant, and therefore a deficiency is most likely to be seen in the younger tissues first. Boron deficiency was badly seen in vegetable crops grown in Dupahad cluster. It was deficient in soils of all the villages in the cluster. Tomato crop showed boron deficiency to a larger extent.
Participatory soil sampling Soil samples from 286 farmers’ fields covering 9 thandas in Dupahad cluster of Nalgonda districts were collected during 2009 with farmer participation in soil sampling (Fig. 9). After conducting farmers’ meeting in each village and depending upon soil type, crop, slope and management, about 30% of farmers’ fields were selected for sampling using stratified random methodology. The identified farmers were made into groups for a demonstration of soil sampling procedure. Collected soil samples were labelled with cluster name, village name and farmer’s name. In most of the clusters, village sarpanch or village head was involved in participatory soil sampling. Collected soil samples were analyzed in the soil chemistry laboratory at Gaddipally and CRIDA
The soil pH was measured by glass electrode using a soil to water ratio of 1:2; electrical conductivity (EC) was determined by an EC meter using a soil to water ratio of 1:2. Organic carbon was determined using the Walkley-Black method (Nelson and Sommers 1996). Available N was determined by alkaline permanganate method (Subbiah and Asija 1956). Available P was determined by Olsen (Olsen and Sommers 1982) , and Bray methods, respectively in neutral to alkaline and acidic soils, K by neutral normal ammonium acetate method (Hanway and Heidel 1952),
Fertility status of the soils of Dupahad cluster
Soil fertility of the cluster of villages was carried out with farmer participation. Soil reaction, electrical conductivity and fertility status of soils of different villages in the cluster are presented in Table 4. Soils of Dupahad cluster in Nalgonda district showed pH ranging from acidic to the alkaline range.
- Centrial institue of dryland agriculture