Crop-Livestock Integration Benefits
Lourival Vilrla, Manuel Claudio Motta Macedo, Geraldo
Bueno Martha Júnior and João Kluthcouski
The development of alternatives for the reestablishment of the production capacity of cultivated pastures is fundamental to achieve the sustainability and intensification of the pastoral activity in the Cerrado regions. Some of the viable options suggested are the integration of the systems of grain and livestock production, together with direct planting. These systems have the potential to increase production and reduce risks of degradation while improving the soil chemical, physical and biological properties and the productive potential of grains as much as forage.
The innumerable benefits of the crop-livestock integration can be synthesized as: agronomic, through the recuperation and maintenance of the soil productive capacity; economic, by means of product diversification and higher yields and quality at less cost; ecological, through the reduction of crop pests and consequentially less pesticide use as well as erosion control; and socially by more uniform income distribution as the livestock and crop activities separately concentrate income generation. The higher generation of direct or indirect tributes as well as reduced urban migration also need to be considered. The cost of the creation of a new job in rural areas is much less than in urban.
New benefits inherent to the crop-livestock integration are constantly being seen by researchers and farmers and some of these are covered in more detail in this chapter.
Soil improvements, Productivity and Production System Economics
The complex of the advantages of the crop-livestock integration are still not totally qualified nor even quantified. However, present knowledge indicates that this practice will surely be the basis of the sustainability of crop and livestock production in the Cerrados. Most of the tropical forages are known for their adaptation and tolerance/resistance to biotic factors that affect annual crops. In respect to soil treatment maintenance of forage crops is the minimum possible. On the other hand, in the most varied annual crop production systems in the Cerrados biome, the application of soil correction and mineral fertilizer in balanced quantities has been necessary to achieve good harvests. In time, the continual use of these inputs improve/correct the soil chemical fertility. However, the intensively mechanized production of annual crops can result in the physical soil degradation, such as compaction and de-structuring as well as reduction of organic matter, even when using the traditional rotations. Also, a significant increase in the number of biotic crop pest species can occur, with a consequential reduction in productivity and increased costs of pesticide use.
The pastures, on the other hand, exhaust the residual crop nutrients but can recycle nutrients from deeper soil layers thanks to their abundance and depth of the roots’ exploration. Concomitantly, pastures are optimal accumulators of biomass both in and above the soil, practically during the whole period of non-climatic restrictions and for this reason enrich the soil with organic matter. Beyond this, the main tropical forages, particularly the grasses, have not suffered from many pest and disease attacks that are common in cultivated crops and thus break their cycle. Thus, one can say, that in the integration of these activities there exists a natural exchange of benefits in the sense of recuperating lands degraded by monocropping.
Chemical, Physical and Biological Soil Benefits
The soil organic material (SOM) is often considered as “the soil’s font of life” as it furnishes energy and nutrients for soil organisms, which, in turn, stimulate important activities in the natural and agricultural ecosystems such as carbon (C) and nutrient recycling. In the face of the limited use of soil correctives and fertilizers in the Cerrados region, it is easy to perceive the great importance of the nutritional function of the SOM in these ecosystems.
In addition, the SOM executes other functions vital to the life cycle, such as, for example: a positive action on the activity of soil flora and fauna that help in soil aggregation - favouring a better water infiltration into the soil profile and reduced erosion and run off; the tying up of toxic types of aluminium and manganese through labile (volatile) C composites; increase in the capacity of effective soil cationic exchange (CCE), especially in soils with a pH greater than 5,5 that determines the better storage and retention of nutrients; better soil water storage capacity; positive action on the stability of soil aggregates, porosity and density; and contribution to decreased soil compaction. (Silva and Resck, 1997; Stevenson and Cole, 1999; Macedo, 2000; Craswell and Lefroy, 2001; Martius et al., 2001 and Palm et al., 2001).
However, over years of crop cultivation, the loss of SOM is constant and consequently there is a compromise of the physical, chemical and biological quality of the soil. (Vilela et al., 1999 and Martius et al., 2001). In the contrary, the pastures, especially when well managed, have the capacity to maintain or even improve the level of soil organic matter as opposed to annual crops.
Figure 1 shows that soybean monoculture over 13 years in a very clay red-yellow latosol in Cerrado vegetation reduced the initial level of SOM of 3,6% by 24,4%. On the other hand, soil covered with Brachiaria humidicola, managed and cut over 9 years, gave a continual increase in the SOM level that started to decrease when the system returned to annual crops (soybean-maize rotation). However, one can see that, up to the last year, the soil covered with pasture maintained a difference of 30% in relation to the annual crop rotation system (Sousa et al., 1997). Under pastoral conditions with good management, the SOM increase through the same pasture can even be higher as understood by the overview presented by Corsi et al. (2001).
The positive soil chemical and physical effects of the pasture/crop rotation were evident from the work of Greenland (1971) and White et al. (1978). In an overview on soil use systems with pastures and crops these authors discussed the need to increase the use and efficiency of these systems for a better water and N use. Similarly, the work of Díaz Rosello (1992) showed a reduction of 2% in relation to C/N in a continuous crop sequence area, this was due to the reduction of total N, mainly when legumes were not rotated. This supports the idea that pastures are more efficient nutrient recyclers than crops (Greenland, 1971; White et al., 1978 and Vilela et al., 2002).
In fact, Greenland (1971) in a study on crop/pasture rotation, showed that the N stored over the years by the inclusion of grass pastures had a direct and positive effect on wheat production when sown in succession.
Results favouring the P balance in areas of crop-pasture integration when compared to continuous agricultural systems using fertilizer have also been observed (Moron and Kiehl, 1992). Souza et al. (1997) showed that the first soybean crop productivity after nine years of pasture (rotation system pasture/crops), was superior to the annual crop system (13th soybean crop) for the same level of soil P (Figure 2), showing the greater use efficiency of this nutrient. As an example one sees that 6 mg dm-3 of soil P (Mehlich 1) were needed in order to produce 3t/ha of soybean in the annual crop system while in the pasture/annual crop system the need was only 3 mg dm-3.
The lower critical level of P in the pasture-soybean rotation could be a consequence of recycled P from SOM mineralization accumulated during the pasture period and/or blockage of the P adsorption sites by greater SOM accumulation, thus reducing P fixation (Fox and Searle, 1978). These results show the better use efficiency of P by plants in an annual crop-pasture rotation than in an annual mono-cropping system.
It has also been seen that the pastures are more efficient in the use of soil P than the annual crops. Goedert et al. (1986) showed that Bracharia humidicola was more efficient than soybean in the uptake of residual phosphorous (Figure 3). These authors observed that, in seven years of cultivation, soybean extracted 12 kg/ha of P2O5, while that two years of soybean followed by five years of pasture extracted about 50 kg/ha of P2O5 from the system.
According to Sousa et al. (1977), another way to evaluate P use efficiency is the soybean yield per unit of residual soil P. Table 1 shows that this yield, in the annual crop-pasture system, was on average double that of the continuous annual crop system. The results obtained by Sousa et al. (1997) show furthermore that, generally, the annual crop-pasture system recuperated more P than the annual. On overage the annual crop-pasture system recuperated 61% of applied P and the annual system 37%.
Table 1. Soybean production in the 13th year in response to residual P from single super-phosphate applications in the systems annual crop-pasture and annual in a clay-texture red-yellow latosol.
Table 2. Total amount of P exported from some treatments of P top-dressed in the first year of 17 years of cropping in areas with the systems annual crop-pasture and annual in a clay-texture red-yellow latosol.
Ayarza et al. (1993) showed positive results in the improvement of soil physical properties, such as the stability of aggregates, in the system crop and livestock at the Santa Terezinha farm in Uberlandia, Minas Gerais. Pastures seeded in sequence to crops rapidly increased aggregates’ stability, even superseding the natural vegetation, and proving the important contribution of the extensive and deep root system of the grasses in the aggregation of soil particles. The level of soil organic matter also evolved in the rotation, passing from 0,84-0,94% in the mono-cropped areas to 1,23% in the crop/pasture sequence.
The integrated use of crop and pasture has also stimulated the interest of farmers seeking to diversify their production systems and to overcome the problems arising from successive annual crops such insect pests, weeds and diseases. It is known, for example, that the forage grasses are highly resistant to the majority of pests and diseases and thus can break the cycle of damaging biotic agents, resulting in less use of pesticides (Kluthcouski et al., 2000 and Oliveira et al., 2001).
In fact, Kluthcouski et al. (2000) indicated that the brachiaria straw has contributed immensely to the reduction in the intensity of attack of some soil-borne diseases (white mould and root rots caused by Rhizoctonia solani and Fusarium solani f. sp. phaseoli) in the black bean crop compared to straw residues of rice and particularly of soybean and maize. Cobucci et al. (2001) further indicated that the crop-pasture was effective in reducing weed emergence in black beans in the winter (Figure 4). According to the authors the break in the weed cycle lessened the incidence.
Another positive biological effect coming from the crop-pasture integration was observed by Vilela et al. (1999). They suggested that the interruption of the annual crop cycle by the introduction of the consortium of Andropogon gayanus/Stylosanthes guianensis cv ‘Minerão’ reduced the soil nematode population (Table 3).
Table 3. The effect of cultivation systems on nematode populations in a clay-texture red-yellow latosol.
Apart from the beneficial effects of crop-pasture integration on pest and disease incidence, positive effects on root association with arbuscular mycorrhizal (AM) fungi have been observed. These increase the plant’s capacity to absorb soil nutrients, particularly P, improving the response to various fertilizers and correctives, thus benefiting production (Miranda et al., 2001). In Table 4 it can be seen that the forages were more efficient in the quantitative population increase of native AMs than soybeans at the time of establishment (first cultivation in 1992) of these crops. However, from the second planting on, the perennial forages became less dependant on AMs and the AM sporulation and root colonization was less and similar to that of the crops. Also, these attributes generally increased with time in the annual crops.
A non-adequate crop sequence could result in a selective accumulation of AMs in the soil, which may be inefficient for future plantings. Rotations with different crops would be needed to alter the qualitative composition of the AMs with a view to re-establishing a new equilibrium between the fungal species that would be efficient for a greater number of plant species.
Table 4. Population density of native arbuscular mycorrhizal fungi in the soil, sampled at different times, in function of the soil-use systems: NC = native Cerrados; Ag = Andropogon gayanus; Ag+leg = A. gayanus/Stylosanthes guianensis cv ‘Minerão’; Crops - S= soybean and M = Maize. (Averages of two replicates).
In this manner, the quantitative alteration observed in Cerrados soil cultivated with forages and annuals (Table 4) was accompanied by an alteration in the number of species when crop rotation was realized (Table 5). This rotation occurred in the rainy season of 1995/1996 and when the areas with intercropped pasture were cultivated with maize and, in the areas with annual crop, intercropped pastures were established (A. gayanus/S. guianensis cv ‘Minerão’). The introduction of annual crops in the area previously occupied by forages re-established the number of native AM species, this was also found in the area cultivated with annual crops.
Table 5. Effect of cropping systems on the dynamics of species of arbuscular mycorrhizal fungi present in a dark red Cerrado latosol. Ag + legumes = Andropogon gayanus intercropped with a legume cocktail (Calopogonium mucunoides, Stylothanthes guianensis cv ‘Minerão’, centrosema and perennial soybean); Crop = 1994/95 - maize; 1995/96 - soybean.
Benefits in the Productivity of Grain Crops and Forages
Ayarza et al. (1993) found that the yield of grains was positively correlated with the age of the pasture that preceded the annual crops in rotation and that an increase of 127 kg of grain occurred for each year of pasture. However, in some cases, the rotation with pastures did not show evident effects on maize and soybean grain yields (Figure 5). In other cases the soybean yield was even reduced by 11 to 27% in relation to mono-cropping, meanwhile the maize and sorghum grain yields did not suffer significant decreases in areas intercropped with crop and pasture (Table 6). Faced with these results, the need to minimize the competition of the forage with the annual crop became evident, either by means of under-application of herbicide levels or by sowing the forage in post emergence, in the sense of guaranteeing satisfactory grain yields (Cobucci et al., 2001).
Table 6. Yields of maize, sorghum and soybean grains and maize and sorghum forage in function of the presence or not of intercropped crop and pasture.
Contrarily, the responses in forage production are generally positive in the integration crop-pasture, because the pastures respond promptly to the greater nutrient supply, which stays in the soil as a result of the area being used for crops (Figure 6). As a result, the support capacity of the pasture and the system’s productivity are substantially elevated in relation to the results seen in degraded pastures (Table 7).
Table 7. The support capacity and development of cattle reared (from 9 to 24 months old) in pastures renewed with different strategies and submitted to a pasture pressure (PP) of 7% in a sandy soil in the municipality of Brasilândia, Minas Gerais.
Similar results to those shown in Table 7 have been observed in an experiment started in 1993/1994 at the Embrapa Beef Cattle Station in Campo Grande.
The project was installed in an area of degraded Brachiaria decumbens pasture, which was recovered or recuperated through different treatments: fertilizing, liming and mechanical means; renovation with a change of species - Brachiaria brizantha and Panicum maximum, with sowing of soybean or maize etc. according to the various treatments. An area of natural vegetation and one of degraded pasture were maintained as controls for comparison.
The main treatments constituted five production systems: S1 = continual pasture; S2 = continual cropping; S3 = pasture for four years - crops for 4 years; S4 = crops for four years - pastures for 4 years; S5 = crop for one year - pasture for three years (established in the second year with or without a maize crop). These systems were subdivided into subsystems composed of soil preparation methods and cultivation methods: conventional and direct drilling, summer crop and summer + winter crops; forage maintenance fertilizing and crops intercropped or not with forage legumes in a total of 12 treatments (for more information see Macedo, 2001), details are as follows:
System 1 = continual pasture;
System 2 = continual cropping (CC);
System 3 = pasture for four years - crops for four years;
System 4 = crops for four years - pastures for 4 years;
System 5 = crop for one year - pasture for three years;
The animal production results (Table 8) show that pastures of Brachiaria decumbens recuperated in 1993/94 (S1) could produce about four to five times more than degraded pastures (DP). The residual fertilizer effect (1993/94) was sufficient in order not to differentiate between the treatments with and without maintenance fertilization through three animal cycles as well as the animal production. However, from the fourth cycle (1997/98) the production of pastures with maintenance fertilization and with maintenance fertilization and legumes, PCCA and PCAL respectively, became superior with significant differences over the pasture without maintenance fertilization (PCSA). It is emphasized that the treatment with legumes (stylothanthes and calopogonium) gave a production systematically superior in the order of 15 kg of meat/ha/year. The animal production in pastures in the crop/pasture systems S4 and S5 gave productions in the order of 689 to 789 and 591 to 842 kg live weight/ha respectively. With the exception of S4 where pastures of Panicum maximum cv ‘Tanzânia’ received maintenance fertilizer of N (50 kg/ha/year), the B. brizantha pastures (S5) did not receive any maintenance and were managed only with the residual soybean fertilizer in the first year. In both systems a decrease is already seen in the animal stocking rate as a result of decreased soil fertility, principally phosphorous (Macedo, 2001).
Table 8. Animal production (carcas equivalent kg/ha) in continuous pasture systems and in integrated systems of crop and livestock in a dark red clay latosol. Campo Grande, Mato Grosso do Sul.
However, greater weight gains will be associated with adequate pasture management (i.e. availability of forage) and with attention to sanitary aspects and animal reproduction. Obviously, the genetic potential for animal weight gain is important to assure more satisfactory results (Magnobosco et al., 2001). Furthermore, it is important to bear in mind that a greater forage production allows higher stocking rates, as much in the dry as in the wet season (Magnobosco et al., 2001), however the seasonality in forage production is not significantly altered whatever the forage species in question (Figure 6).
Benefits for the Production System Economy
Various studies on crop-pasture integration have produced interesting economic results (Yokoyama et al., 1999; Cezar et al., 2000 and Macedo, 2001). In the study which was being done through the Embrapa Beef Cattle Station for example, the preliminary economic analysis of the results of six years of soybean production, two of maize and of five livestock cycles showed that the crop-livestock integration could be a viable option to minimize agricultural business risks (Costa and Macedo, 2001). The comparisons were carried out by taking into consideration animal production in degraded pasture as the control. There were also simulated comparisons with prices of soybean, maize, cattle weight and fertilizer, varying 20% above or below historic prices. The results are shown in Table 9.
Table 9. Net present value (NPV) of the additional cash flow per hectare for various combinations between prices of cattle, soybean, maize and fertilizer, for continuous pasture and integrated crop-pasture systems when compared to a degraded pasture. Values expressed in Reais (R$); numbers in brackets represent the decreasing order of advantage between the different systems as regards the NPV.
The S5 system, subsystem L1P3Mi; characterized by one year of soybean/millet and 3 years of Brachiaria brizantha cv ‘Marandu’, installed simultaneously with maize, was in first place in various simulations as regards the NPV. This treatment offers a cash flow with the incoming from sales of soybean, millet and meat and appears to be very attractive as the preliminary economic evaluation shows (Table 9). It is worth highlighting that, with the increase in price of fertilizers, its application in pastures with maintenance fertilizer (PCCA and PCAL) makes its position unfavourable as compared with the crop-livestock integration systems.
As for the S4 system, with four years of soybean cropping and subsequent implantation of Panicum maximum cv ‘Tanzânia’, one notes a significant increase in animal production in the first and second husbandry cycles, with a fall in the third (results not presented). Seeing that only nitrogen maintenance fertilizing (50 kg N/ha/year) was used without P and K, and with the hypothesis of the use of residual soybean fertilizer, the resulting productivity favoured its position in the comparative scores.
It is important to note that the annual soybean fertilizing considerably increased the levels of available soil P. However, pasture cultivated without maintenance fertilizer for four years after the soybean cycle accentuated the decline of soil P levels, an essential production nutrient (Macedo, 2001). Perhaps S4 would not be a favourable strategy, as the return to the four-year cycle soybean crop would involve more costly soil corrections for the farmer.
A conclusive analysis of the performance of the different systems will only be possible at the very end of the crop and livestock cycles, after eight years. However, various hypotheses are being verified, at least partially: the improvement of soil fertility by the crops, of the soil physical properties by the pastures and the favourable cash flow of the integrated crop-pasture systems.
Even though the crop-livestock integration could be an extremely important alternative from the point of view of sustainable animal production; farmers who already practice it having a considerable advantage of the others, it demands various prerequisites in order to be used. Given the limits of infrastructure, financial resources, technical knowledge, personal capacities and social barriers to its adoption it is probable that this system would be implemented by a smaller proportion of farmers in relation to its potential area of use (Macedo, 2001 and Vilela et al., 2002). Yokoyama et al. (1998) effectively highlighted that the greatest obstacles to the adoption of this technology are the absence of appropriate on-farm machinery and its respective adoption costs.
To conclude, it is important to remember that, as well as the benefits mentioned in this work, the integration of crops and pastures brings social benefits due to the direct and indirect creation of employment and also favours reduction of migration to urban areas (Kluthcouski et al., 2000).
Spain et al. (1996), Broch et al. (1997) and Cardoso (2000) summarized and enumerated the many advantages of the crop-livestock integration with much authority as presented in the following.
Benefits of Cropping for Livestock Production
Experience has shown that the perennial forages, principally the brachiaras, are more productive in the first year following establishment; also staying green during the main part of the dry season. As an example of this Broch et al. (1997) obtained meat yields of 375, 225 and 135 kg/ha/year in the first, second and third respectively of pasture after the soybean crop.
Other advantages of agriculture for crop husbandry speak of the faster return on capital investment, pasture recuperation, economy perennial pasture establishment and the ease of changing forage species.
Benefits of Livestock Production for Cropping
A study conducted by Aidar et al. (2000) showed that the intercropping of brachiaria with maize and maize alone produced greater biomass quantities, reaching 17 t/ha of dry material. Three months after desiccation there were still about nine tons of residues. In this same study the authors verified that there were higher yields of irrigated black beans when grown over Brachiaria ruziziensis straw, followed by residues of rice, of Brachiaria brizantha, and of soybean and maize. They also observed the total absence of white mould (Sclerotinia sclerotiorum) in the black beans cultivated on brachiaria straw, while there were severe attacks of this fungus disease when cultivated in the straw of soybean, maize and rice.
Broch et al. (1977) also verified better soybean yields when cultivated over residues of B. brizantha. From the first to the third year of successive soybean cultivation in previous bracharia areas the yield decreased from 3 500 to 3 100 kg/ha.
Advantages of Crop and Livestock Integration
Some additional advantages offered by the brachiarias are reported by Cardoso (2000):
Cardoso (2000) concluded that these observations left little doubt that the brachiaria’s root system promotes the improvement of the soil physical properties, making it friable, loose and soft in benefit of subsequent crops, perhaps through the complimentary beneficial effect of associated fungi. One supposes that brachiaria could favour atmospheric nitrogen-fixing organisms independently of symbiosis. Thus, as soil conditioners and nitrogen fixers, the brachiarias benefit 50 million hectares which they cover in Brazil.
The integration of the grain and livestock production systems constitutes a new paradigm for agriculture and animal husbandry in the Cerrados region. These systems have the potential to increase grain, meat and milk productivity and to reduce the risks of natural resources degradation. The results obtained with crop-livestock integration in the Cerrados show the benefits of this system in agriculture and livestock production and in the improvement of the physical, chemical and biological soil properties. However, the adoption of this practice by the farmers is still very small. This is due, in part, to the greater complexity of the crop-pasture rotation and the need for high investment in the acquisition of machinery and implements.
An association of grain and livestock producers would be one of the alternatives to incentivate the crop-livestock system. Such an association could contribute to increase the cultivated grain area and animal production without the need to open up new Cerrado areas.
The coexistence of well-structured systems of grain and livestock production in the Brazilian Cerrados will be one of the factors, which will contribute, in a determinate manner, to the adoption of the crop-livestock rotation to increase the pasture livestock productivity. In this way the harmonious and sustainable marriage of the livestock and agricultural activities in this region can be foreseen.