G. Kirchhof

The effect of soil puddling on the soil, physical properties and the growth of rice and post-rice crops

Changes in soil physical properties due to traditional methods of puddling for lowland rice (Oryza sativa L.) production and post-rice legumes was investigated in field experiments conducted on three sites in Indonesia and two in the Philippines over a 3-year period. Puddling treatments used in the field were, in increasing order of puddling intensity, dry cultivation prior to submergence, one and two plowing and harrowing treatments using a draught animal and associated implements, and two cultivations using a mechanical roto tiller. Rice was followed by mungbean (Vigna radiata (L.) Wilzek) on all five sites, and in addition soybean (Glycine max L. Merr.) at Ngale and peanut (Aracis hypogaea L.) at Jambegede were also grown. All puddling treatments were followed by post-rice treatments of surface drainage (with and without surface drains) for the Indonesian sites and sowing technique (zero-till-dibble versus plough-broadcast-harrow) for the Philippine sites. Rice yields were highest under the traditional puddling techniques using draught animal traction. Results suggested that puddling with a roto tiller reduced yield because of insufficient depth of puddling, while dry cultivation may have reduced yield due to increased soil strength of the puddled layer; both are thought to limit root development. Puddling had no significant effect on post-rice mungbean and peanut production. However, results showed that increasing puddling intensity tended to reduce soybean yield. Dry cultivation of lighter textured, well drained soils such as at Manaoag, tended to require more intensive weed control in both rice and dryseason crops compared to higher puddled treatments. Weed infestation was thought to be the largest contributing factor for reduced mungbean yield at Manaoag. Increasing soil puddling intensity at Ngale and Jambegede appeared to reduce root growth. Soil water depletion tended to be smaller in the plough layer that was cultivated under wet conditions compared to pre-rice dry land preparation. Soil water extraction was small and root proliferation was upto 40 cm depth under wet conditions where plant water requirements were met from seasonal rainfall. Root proliferation was deeper and soil water use greater under dry climatological conditions. Small amounts of subsoil water use resulted in substantial yield increases ranging from 3-24 kg mm of soil water used, reinforcing the important role of subsoil water storage and use by the dry season crop in this farming system

Crop establishment of legumes in rainfed lowland rice-based cropping systems.

Poor crop establishment is one of the major limitations to the production of grain legumes after rice (Oryza sativa L.) in rainfed lowland lice-based cropping systems. The success of germination and emergence of mungbean (Vigna radiata (L.) Wilzek), soybean (Glycine max (L.) Merr) and peanut (Arachis hypogaea L.) planted in zero tilled (ZT), zero tilled combined with mulch application (ZTM) and tilled soils (T) were investigated in a crop establishment trial as a function of sowing delay. Sowing delay was used as a surrogate for soil-water content. This experiment was conducted under a rain-shelter to ensure continuous and progressive drying conditions. A dibbling trial using the same legumes was conducted concurrently and subjected to the: prevailing climatic conditions. Germination and emergence success rate of the traditional dibbling method was compared to dibbling incorporating depth control and seed cover. Both experiments were conducted towards the end of the 1994 rainy season in a Vertisol soil at Ngale and an Andosol soil at Jambegede, in East Java, Indonesia where the season gradually changes from wet to dry season. Mungbean emergence was 93-94% at Ngale and soybean emergence was 83-95% at Jambegede, both in the presence and absence of rain. Peanut emergence was low (50-69%) at both sites. In all three species at both sites, the percentage of seeds that failed to germinate was greater than seeds that failed to emerge, indicating that germination rather than emergence was limiting. Seed rot caused by fungal attack and poor imbibition associated with poor seed-soil contact (observed as intact seeds) were the main constraints for the success of germination of mungbean, soybean and peanut. Thr failure to emerge was mainly caused by seedling rot and the failure of hypocotyl and radicle to penetrate the hard soil, observed as a culling of the hypocotyl, Cultivation at Ngale on a Vertisol resulted in excessively cloddy soil, which in turn resulted in a significant decrease in germination and emergence. The application of straw mulch had little effect on the emergence of legumes on this soil, The use of depth control and application of seed-soil cover did not have a significant effect. Hence the traditional dibbling method where depth of planting ranged from 4 to 7 cm without seed cover was found to be appropriate for planting mungbean and soybean. Germination and emergence of peanut was improved with the application of soil cover and the dibbling stick had a spike added to the tip to assist the root to penetrate the hard compacted soil

A preliminary diagnosis and recommendation integrated system (DRIS) model for diagnosing the nutrient status of sweet potato (Ipomoea batatas)

Critical leaf nutrient concentrations have often been used to diagnose the nutritional causes of crop underperformance. Unfortunately, these diagnostic criteria are not available for mature, tuber-bearing sweet potato plants (the word ‘tuber’ being used to describe a swollen root rather than a swollen stem). The Diagnosis and Recommendation Integrated System (DRIS), however, provides a reliable means of linking leaf nutrient concentrations to the yield of sweet potato tubers, and may be developed for this crop using existing data from regional crop surveys. In the present study, tuber yield and leaf nutrient concentration data from a survey of sweet potato gardens conducted in the Papua New Guinea (PNG) highlands in 2005 were used to establish DRIS N, P, K, and S norms and statistical parameters for sweet potato. Although the database was relatively small, the norms derived for nutrient ratios of key biological significance, i.e. N/S and K/N, were within the expected narrow ranges for higher plants, giving credibility to both the database and the DRIS model. Data from future surveys and field trials may subsequently be used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of diagnostic scope to include other macro and micro-nutrients. As it stands, though, this preliminary DRIS model for sweet potato is possibly the best diagnostic tool currently available for evaluating the N, P, K and S statuses of sweet potato crops in the pacific region.

An evaluation of nutritional constraints on sweet potato ( Ipomoea batatas ) production in the central highlands of Papua New Guinea

Sweet potato (Ipomoea batatas) is the staple food crop in the highlands of Papua New Guinea (PNG). Declining crop productivity, however, appears to be threatening the sustainability of sweet potato-based farming systems within the region, a probable cause being the exhaustion of soil nutrient reserves in continuously cultivated sweet potato gardens. To assess the extent of the problem, a survey of sweet potato gardens was conducted across four of the highlands provinces and information on soil and crop variables was obtained for old gardens (cultivated over many seasons) and new gardens (newly brought into cultivation) on soils of volcanic and non-volcanic origin. Crop leaf nutrient data collected in the survey were interpreted using the Diagnosis and Recommendation Integrated System (DRIS), to try to identify the main nutritional constraints on tuber production in different garden types on soils of volcanic or non-volcanic origin. The results suggested that K deficiency was the primary cause of poor crop production in almost a third of sweet potato gardens, but was more of a problem in old gardens than in new. Phosphorus deficiency was also a problem on volcanic soils, and S deficiency on non-volcanic soils. These latter deficiencies, however, were at least as prevalent in new gardens as in old. Important factors contributing to K and S depletion from garden systems were the removal of K and S-rich vines from cultivation areas, the shortening of fallow periods and the burning of weed and crop residues, the latter releasing S (SO2) to the atmosphere. Correction of K and S deficiencies may require the recycling of old vines back to sweet potato cultivation areas and the adoption of a zero-burn policy for fallow management. Correction of P deficiency may necessitate the use of P-accumulating fallow species, e.g. wild Mexican sunflower (Tithonia diversifolia), to extract the P fixed by sesquioxide and allophanic minerals

Low input tillage/cropping systems for limited resource areas

Agriculture in limited resource areas is characterized by small farms which an generally too small to adequately support the needs of an average farm family. The farming operation can be described as a low input cropping system with the main energy source being manual labor, draught animals and in some areas hand tractors. These farming systems are the most important contributor to the national economy of many developing countries. The role of tillage is similar in dryland agricultural systems in both the high input (HICS) and low input cropping systems (LICS), however, wet cultivation or puddling is unique to lowland rice-based systems in low input cropping systems. Evidence suggest that tillage may result in marginal increases in crop yield in the short term, however, in the longer term it may be neutral or give rise to yield decreases associated with soil structural degradation. On marginal soils, tillage may be required to prepare suitable seedbeds or to release adequate Nitrogen through mineralization, but in the longer term, however, tillage reduces soil organic matter content, increases soil erodibility and the emission of greenhouse gases. Tillage in low input cropping systems involves a very large proportion of the population and any changes: in current practices such as increased mechanization will have a large social impact such as increased unemployment and increasing feminization of poverty, as mechanization may actually reduce jobs for women. Rapid mechanization is likely to result in failures, but slower change, accompanied by measures to provide alternative rural employment, might be beneficial. Agriculture in limited resource areas must produce the food and fiber needs of their community, and its future depends on the development of sustainable tillage/cropping systems that are suitable for the soil and climatic conditions. These should be based on sound biophysical principles and meet the needs of and he acceptable to the farming communities. Some of the principle requirements for a sustainable system includes the maintenance of soil health, an increase in the rain water use efficiency of the system, increased use of fertilizer and the prevention of erosion. The maintenance of crop residues on the surface is paramount for meeting these requirements, and the competing use of crop residues must be met from other sources. These requirements can be met within a zonal tillage system combined with suitable agroforestry, which will reduce the need for crop residues. It is, however, essential that farmers participate in the development of any new technologies to ensure adoption of the new system

Soil organic carbon and total nitrogen under Leucaena leucocephala pastures in Queensland

Soil organic carbon (OC) and total nitrogen (TN) accumulation in the top 00.15m of leucaenagrass pastures were compared with native pastures and with continuously cropped land. OC and TN levels were highest under long-term leucaenagrass pasture (P0.05). For leucaenagrass pastures that had been established for 20, 31, and 38 years, OC accumulated at rates that exceeded those of the adjacent native grass pasture by 267, 140, and 79kg/ha.year, respectively, while TN accumulated at rates that exceeded those of the native grass pastures by 16.7, 10.8, and 14.0kg/ha.year, respectively. At a site where 14-year-old leucaenagrass pasture was adjacent to continuously cropped land, there were benefits in OC accumulation of 762kg/ha.year and in TN accumulation of 61.9kg/ha.year associated with the establishment of leucaenagrass pastures. Similar C:N ratios (range 12.714.5) of soil OC in leucaena and grass-only pastures indicated that plant-available N limited soil OC accumulation in pure grass swards. Higher OC accumulation occurred near leucaena hedgerows than in the middle of the inter-row in most leucaenagrass pastures. Rates of C sequestration were compared with simple models of greenhouse gas (GHG) emissions from the grazed pastures. The amount of carbon dioxide equivalent (CO 2-e) accumulated in additional topsoil OC of leucaenagrass pastures ≤20 years old offset estimates of the amount of CO2-e emitted in methane and nitrous oxide from beef cattle grazing these pastures, thus giving positive GHG balances. Less productive, aging leucaena pastures 20 years old had negative GHG balances; lower additional topsoil OC accumulation rates compared with native grass pastures failed to offset animal emissions.

Soil puddling for rice production under glasshouse conditions—its quantification and effect on soil physical properties

The effect of soil puddling on soil physical properties of 3 different textured soils (clay, loam, and silty loam) and growth of rice (Oryza sativa) on these soils was investigated under glasshouse conditions. Puddling intensity was expressed as the ratio of soil volume subjected to the puddling implement and the total soil volume in the puddled layer, thus integrating the effects of speed and time of the puddling operation. This parameter was well related to soil dispersion, bulk density, and saturated hydraulic conductivity. However, following prolonged periods of submerged conditions during rice growth, saturated hydraulic conductivity decreased with a decrease in soil dispersion, in contrast to an expected reduction in saturated hydraulic conductivity with increased dispersion. There was indication that continuous waterlogging reduced the effect of soil puddling, in particular on heavy-textured soils.

The soil and climate characterisation of benchmark sites for lowland rice-based cropping systems research in the Philippines and Indonesia.

Soil morphological, physical, chemical and mineralogical properties are described at five locations in major rice (Oryza sativa L.) growing areas of the Philippines (two sites) and in Indonesia (three sites) which were selected for lowland rice-based cropping systems research. The data were used to classify the soils into the local soil series, soil taxonomy and The Australian Soil Classification systems. These data were intended to facilitate transfer of knowledge of improved farming systems technology to other lowland rice growing areas in the regions. The soils were classified as Andsisols, Inceptisols and Vertisols, and were characterised by clay contents ranging from 370 to 870 g kg and cation exchange values ranging between 17 and 68 cmol (p+) kg for whole soil. pH values were neutral to mildly alkaline. Land surface and root zone attributes were qualitatively evaluated for limitations to post-rice crop production by interpretation of modified surface and sub-soil properties associated with rice production. Leakiness of bunds was also examined and mainly attributed to biological activity and for the development of drainage channels. Climatic data are presented for each of the five sites and the characteristics for potential rainfall incidence are given for the post-rice dry season crop period. The soil sites selected have a range of properties which are deemed to represent large areas of soils used for rice production in these two countries

Growth and yield response of grain legumes to different soil management practices after rainfed lowland rice

Field experiments were conducted over a 3-year period (1992-1995) in Sulawesi, East Java and the Philippines to investigate the response of post-rice (Orzya sativa L.) soil managements on growth and yield of legumes after lowland rice under rainfed conditions. Grain Legume yields ranged from complete crop loss due to excessive rainfall after sowing to a maximum of 1.08 Mg ha(-1) fur mungbean (Vigna radiata (L.) Wilzek), 1.33 Mg ha(-1) for soybean (Glycine max L. Merr.) and 2.3 Mg ha(-1) fur peanut (Aracis hypogaea L.). The response and magnitude of the effects from different management systems on legumes were closely related to the climatic conditions prevailing during the crop establishment phase. Correct timing of legume sowing was seen as the most important factor determining successful moderate crop production, followed by the availability of subsoil water reserves. Tillage was considered a potential method to improve yields because sowing could be carried out later during the dry season when rainfall was more predictable. Tillage, provided it is carried out at suitable soil water contents, could probably partially overcome the adverse soil physical condition induced during the rice phase. Fertiliser application tended to increase food legume in wetter areas showing that residual fertiliser effects from the previous rice crop could he limiting. In drier areas, fertiliser application had little effect on grain legume yields. Mulch as a soil amendment tended to increase yields in drier areas due to its water conservation effect. In wetter areas mulching was not necessary and could even lead to yield reduction if conditions were too wet

Lime-slotting technique to ameliorate subsoil acidity in a clay soil. II: Effects on medic root growth, water extraction and yield

Subsoil acidity causes low crop production, which is often associated with shallow root development and restricted soil water extraction. In part I of this series, lime-slotting of an acid soil was shown to improve the soil physical and chemical characteristics for root growth. In a lysimeter study on an acid soil, the effects of several soil ameliorative treatments on root growth, water extraction and yields of a medic crop were evaluated. Large lysimeter cores of 0.75 m diameter and 1.35 m deep were used. The soil treatments included a non-ameliorated acid soil, lime-slotting with a 0.15 m wide and 0.8 m deep slot containing 20 t ha-1 of lime, lime-slotting combined with surface phospho-gypsum application at 10 t ha-1, and complete amelioration of the entire soil volume by mixing lime at 133 t ha-1 and repacking to a low bulk density of 1.1 t m-3. In the non-ameliorated acid soil, medic roots were confined to the surface (0.1 m) layer, resulting in limited water extraction of 32 mm during a prolonged drying cycle, and a low dry matter yield of 70 g m-2. In the lime slotted soil, roots grew within the slot to its full depth, although penetration into the undisturbed soil was restricted to the soil immediately adjacent to the slot. Consequently, the root length per unit surface area (La) at depths below 0.1 m depth was increased to 9.9 km m-2. During a drying cycle, water extraction increased to 58 mm. The increased water extraction came from both the slotted soil and the undisturbed soil between slots. This led to an increase in dry matter yields to 270 g m2. In lime-slotted soils with surface gypsum applications, the root growth and crop water extraction patterns were similar to the lime-slotted soil. Repacking limed soil resulted in similar root lengths (L(a) 10.0 km m-2) as lime-slotted soil. However, owing to more uniform distribution of roots in the repacked soil, water extraction was increased to 100 mm and yields increased to 590 g m-2. Yields of non-ameliorated soil were only 12% of the repacked, limed soil. However, lime-slotting which involves loosening only 25% of the soil surface area and addition of only one-sixth of the amount of lime required for complete soil amelioration, led to marked increases in yield (46% of the yield of repacked soil). Future field studies are required to evaluate the optimum limed-slot configurations required for different soils, crops and climatic regimes.