Cultivating Diversity: Field Scattering as Agricultural Risk Management in Cuyo Cuyo, Department of Puno, Peru

By Carol Goland, 1993.

Chapter 7 - Inputs to Agriculture: Fertilizers

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make a difference: if the field is located in Paqhchani or Aripo and the crop is papa panq'o the field is likely to receive significantly less N, P, and K than other potato fields.

Table 7.10 presents results of the analysis of variance for NPKtot in potato fields. There is significantly greater NPKtot input in Puna Ayllu than in Ura Ayllu (Table 7.10a). Within Puna Ayllu, the contrast between the Awi Awi fields and the estancia fields is not significant (Table 7.10b). Within Ura Ayllu, for all potato fields, the only significant contrast is between the estancia fields and both the fields of Paqhchani and Aripo. The estancia fields are the most heavily fertilized of all Ura Ayllu potato fields. In Table 7.10c I also have compared NPK totals for the production zones of Ura Ayllu excluding fields cropped in papa panq'o. When calculated this way, the only significant pairwise comparison is between the estancia and the Aripo fields, the least heavily fertilized of all the zones.

FERTILIZATION IN SUBSEQUENT YEARS OF THE ESTANCIA ROTATION

Analyses of the fertilization in subsequent years of the estancia rotation is complicated by the fact that several crops are involved. Principle among them are oca and habas, common lesser crops include isaño and illaco. Oats (avena) and barley (cebada) are planted in small quantities during the fourth year of the rotation. Table 7.11 a and b shows the frequency of fertilization of crops grown in each of the three rotation years.

To streamline the analysis, I concentrate on three broad categories of fields: Tuber fields include monocropped oca fields and mixed tuber fields. Habas fields include those monocropped in habas and habas intercropped with tubers. Illaco fields consist only of those fields monocropped with this cultivar. The few fields cropped in avena and/or cebada, and those "others" which do not fall into any of these categories, have been excluded from the analysis (nine fields in total, leaving 159 fields from Ura Ayllu and 126 from Puna Ayllu).

Inter- and Intra-Community Differences in Fertilizer Types and Quantities

In contrast to the ubiquitous fertilization of the potato fields, only about half of the fields in subsequent years of the estancia rotation are fertilized (Table 7.11a). Of the total 126 Puna Ayllu estancia fields in these rotation years, 71 (56%) went without fertilizer inputs. Seventy-five out of 159 (47%) of the Ura Ayllu estancia fields in the second, third, and fourth year of the rotation were not fertilized. When fields during these years were fertilized they were less likely to receive multiple types of fertilizers. In short, fertilization of the non-first year estancia fields is considerably less complex.

It is important to determine whether it is rotation year or crop which affects these decisions. For the second and fourth year of the rotation, it is difficult to separate the two variables, since crop choice is fairly uniform. In Ura Ayllu 95% of second year fields are tuber fields and 91% of fourth year fields are habas fields. In Puna Ayllu, all of the second year fields are tuber fields and 98% of the fourth year fields are devoted to habas. Only in the third year of the rotation is there diversity with respect to the crop grown. In Ura Ayllu, 52% of these fields were planted in oca alone or oca intercropped with isaño and/or illaco, 32% were planted with habas or habas mixed with tubers, and 14% were monocropped with illaco. The proportion of crops in the third year of Puna Ayllu is quite different: only 2% of fields were planted in either oca alone or oca with the minor tubers, 73% were planted in habas or habas intercropped with tubers and 22% were monocropped illaco.

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In Ura Ayllu's estancia manda, the proportion of fields in each year of the rotation which received fertilizer inputs was Year 2: 37%, Year 3: 56.4%, and Year 4: 66%. These differences are significant (Chi-square p=0.010) (Table 7.11b). In Puna Ayllu, the trend is the same but the values are not statistically significant (Chi-square p=0.525). In the second year of the rotation 38.1% of fields were fertilized, in the third year, 40.9% were, and the in the fourth year of the rotation, 50% of fields were fertilized.

Comparing the treatment of the same crop in different years of the rotation can help to disentangle the two variables. No significant difference was found in the proportion of second and third year tuber fields fertilized. For the estancia as a whole, 36.2% of tuber fields in the second year of the rotation, and 43.3% of fields in the third year of the rotation were fertilized (Chi-square p=0.481). For Ura Ayllu only, 34.6% of second year fields, and 44.8% of third year fields were fertilized. (Chi-square p=0.365.) The same comparison can be made for habas fields. In the estancia as a whole, 45.1% of third year, and 59% of fourth year habas fields were fertilized (Chi-square p=0.123). For Ura Ayllu alone, the proportions were 72.2% of third year, and 66.0% of fourth year fields (Chi-square p=0.629). Finally, in Puna Ayllu, 30.3% of third year habas fields and 50% of fourth year habas fields were fertilized (Chi-square p=0.089). It appears that there is no significant difference in the proportion of fields of a given crop that are fertilized in different years of the rotation cycle.

Another way to approach this question is the see whether different crops grown in the same rotation year are treated differently. The third year of the rotation is key. I distinguish between tuber fields, habas fields, and monocropped illaco fields (as defined above). For both estancia mandas combined, although not statistically significant (Chi-square p=0.102), the trend is for the highest proportion of fertilization in the illaco fields (72.2%), followed by a sharp decline for habas (45.1%) and tuber fields (43.3%). In Ura Ayllu, the trend is different (again, not statistically significant, Chi-square p=0.171). The highest proportion of fertilization in the third year is associated with the habas fields (72.2%), followed by the illaco fields (62.5%), and then the tuber fields (44.8%). In Puna Ayllu, a much higher proportion of the illaco fields are fertilized (80%) relative to the habas fields (30.3%).

Thus, the results are by no means clear. There seems to be a trend toward greater frequency of fertilization from the second to the fourth year of the rotation cycle. It parallels the greater frequency of fertilization of habas compared to tubers, with the exception of monocropped illaco. If we examine the same crop planted in different years of the cycle or different crops within the same year of the cycle no clear-cut pattern emerges.

It is easy to identify intervening factors which might affect these decisions: initial level of fertilization of the field when it was taken out of fallow; availability of fertilizers, which could be influenced by any number of factors, including the amount of potato land planted by a family (potatoes presumably would have priority for fertilizers); the distance to a field (in several cases reported by informants as prohibitive for transport of fertilizers); or scheduling, since a field weeded twice as opposed to once might have been more likely to receive fertilizer.

The important issue is to determine how to analyze the data on fertilizer use: by crop or by rotation year. In order to facilitate comparison with other studies of Andean agriculture, the data are presented by crop. I will note where pertinent any cases in which year of the rotation seems to be an important factor.

Table 7.12 shows the proportions of fields in each of the two communities which were fertilized with each fertilizer source. The data are analyzed only for those (tuber, habas, and

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illaco) fields which received any fertilization, i.e., only 139 of the original 285 fields.³ Camelid dung is common in Puna Ayllu and absent in Ura Ayllu, although it is used in only 9.1% of Puna Ayllu fields which were fertilized (Table 7.12a). Sheep dung never appears in Puna Ayllu fields but is used in 18.7% of the Ura Ayllu fields fertilized. There is significantly greater use of synthetic fertilizers in Ura Ayllu than in Puna Ayllu fields though again the proportion is not great (16.5% versus 1.8%). Guano de isla was used in 20.9% of the fertilized fields in Ura Ayllu and in only 1.8% of Puna Ayllu fields; this difference is also significant. Ashes are applied in a high proportion of fields in both communities and significantly more often in Puna Ayllu (92.7% of fields) than in Ura Ayllu (74.7%).

Tables 7.12b and c present data for each community individually. In Puna Ayllu (7.12b), where only camelid dung, ash, synthetic fertilizers, and guano de isla were used, no clear pattern of differences between years emerges. In Ura Ayllu (Table 7.12c) the proportion of fields receiving applications of sheep dung, synthetic fertilizers, guano de isla, and guinea pig dung decreased with subsequent years of the rotation. In contrast, the use of ashes increased steadily from the second to fourth year of the rotation.

Ash is the most common source of fertilizer in each community. As a proportion of all fields (including those that were not fertilized), nearly identical proportions were used in Puna Ayllu (39.8%) and Ura Ayllu (41%). As a percentage of only those fields that were fertilized, the 92.7% of Puna Ayllu fields is significantly greater than the 74.7% in Ura Ayllu (p=0.007). The use of ash in these rotation years is, indeed, the predominant form of fertilization in both communities by frequency. Although there is some use of other fertilizers, and differences between the communities with respect to these, their use is relatively infrequent.

Table 7.13 presents the average N, P, and K (on a per hectare basis) for those estancia fields which were fertilized and for which the data are complete. The estancia fields in Ura Ayllu receive significantly greater quantities of nitrogen. The differences between the two communities in phosphorus and potassium (both greater in Puna Ayllu) are not significant. Within each of the communities, when rotation year is considered, the only significant contrast is for nitrogen between each of the rotation years in Ura Ayllu.

For the fields in years two through four of the estancia rotation, the NPKtot index variable is based only on those fields which did receive fertilizers. Analyses comparing the value of NPKtot across the two communities, for various crops within the estancia as a whole, and for the estancia of each community alone identified no significant differences (Table 7.14). No significant differences were found when NPKtot was examined between rotation years: for the two communities combined, within the estancia as a whole, or within either community individually. Differences between crops are compared in the following sections.

FERTILIZATION OF THE TUBERS

Nutrient Requirements

In contrast to potatoes and maize, little work has been done on nutrient requirements of the minor Andean tubers. Cortés (1977) experimented with varying inputs of N, P, and K on

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oca and found that yields did respond to applications of these macronutrients. In experimental studies in Cuzco, oca was found to respond to moderate levels of nitrogen and strongly to large inputs of phosphorus and potassium. This study suggested that the best mix of these nutrients for the oca crop was 60-120-120 (N-P-K) (Tapia 1982). Less is known for isaño and illaco (National Research Council 1989). King (1988, citing Cortés 1984) reports that illaco has been found to respond to inputs of NPK. In Ayacucho, Escobar and Ibañez (1986) found that the highest yields of illaco were obtained with NPK applications of 144-144-96 kg/ha. Padrón's (1982) work with illaco in Ecuador suggests that highest yields are obtained with larger inputs of P, relative to N and K.

Source of Fertilizers - Community Differences

When we examine the difference between the two communities with respect to the fertilizers used for the minor tuber fields, most of the generalized pattern noted above holds true (Table 7.15a). Puna Aylleños do fertilize a small proportion of these fields with camelid dung (12.5% of fields), while it is completely absent in Ura Ayllu. Sheep dung is absent in Puna Ayllu, but utilized in Ura Ayllu (16.1% of fields). Likewise, synthetic fertilizers and guinea pig dung appear in fairly large proportions of Ura Ayllu's minor tuber fields (35.5% and 9.7%, respectively), but not at all in Puna Ayllu. Guano de isla appears in a significantly (p=0.018) higher proportion of Ura Ayllu's fields (38.7%) than it does in Puna Ayllu (6.3%). The predominant fertilizer used is ash. Puna Aylleños fertilize with ash in a significantly (p=0.001) higher proportion of minor tuber fields than do Ura Aylleños (93.8% vs. 45.2%). The higher frequency of ash application in Puna Ayllu remains significant even when these fields are separated into monocropped oca fields and oca intercropped with other tubers.

Analysis of Macronutrients in Tuber Field Fertilizers

The average value of nitrogen received by Ura Ayllu tuber fields that are fertilized is 197 kg/ha while the average value in Puna Ayllu is sharply lower, 10 kg/ha (Table 7.16a). Fields of both communities receive virtually identical quantities of phosphorus and potassium. For phosphorus, the values are 99 kg/ha (Ura Ayllu) and 93 kg/ha (Puna Ayllu); for potassium the quantities are 137 kg/ha in Ura Ayllu and 139 kg/ha in Puna Ayllu.

When comparisons are made between monocropped oca fields and fields planted in oca and other tubers, no significant differences are found. Nor are there any significant differences between tuber fields of the second and third years of the rotation.

Differences in NPKtot in minor tuber fields were examined between the two communities (Table 7.14c) and shown not to be significant. Comparisons of monocropped oca fields and mixed tuber fields, and between fields in the second versus third year of the rotation, also indicated that differences were not significant.

FERTILIZATION OF HABAS

Nutrient Requirements

Little work has been done on the agronomy of Vicia faba or other introduced legumes in the Andean region. For other food legumes worldwide, there is general agreement that yield responds to increased phosphorus. The effect of nitrogen is debated, although for broad beans there is good evidence of response to nitrogen (Sinha 1971).

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Sources of Fertilizer - Community Comparisons

Puna Aylleños used only camelid dung and ashes in fertilizing their habas fields (Table 7.15b). In contrast, Ura Aylleños used ashes along with sheep dung (20.8% of fields), synthetic fertilizers (8.3%), and guano de isla (12.5%). Ash fertilizer in Puna Ayllu was applied to 96.7% of the habas fields which received any fertilizer; in Ura Ayllu to 91.7%. This slight difference is not statistically significant (p=0.380). The same is true of monocropped habas fields. With respect to habas intercropped with tubers, none of the Puna Ayllu fields received fertilizer (out of n=3).

Analysis of Macronutrients in Habas Field Fertilizers

Community differences in application of macronutrients to habas are even less than those for tuber fields (Table 7.16b). The average Ura Ayllu habas field received 33 kg/ha of N, 82 kg/ha of P, and 109 kg/ha of K. In Puna Ayllu the mean values are 35 kg/ha for N, 106 kg/ha for P, and 146 kg/ha for K. None of these differences between the two communities are significant.

When monocropped habas fields are compared to habas intercropped with tubers, one significant difference for N, P, and K arises. In Ura Ayllu, polycropped fields receive significantly more N than monocropped fields (24 vs 66 kg/ha, p=0.032). Other than this, there are no significant differences in the quantity of N, P, and K applied to these fields in different years of the rotation: not within the estancia as a whole, nor within the estancia of the individual communities.

NPKtot was compared between the two communities (Table 7.14c). Differences in the NPK index were examined for habas fields in different rotation years, and between fields of monocropped habas and habas intercropped with tubers. No significant differences were found.

FERTILIZATION OF ILLACO FIELDS

Nutrient Requirements

As noted above, little is known about the nutrient requirements of the minor Andean tubers, including illaco, although illaco does respond to inputs of N, P, and K.

Sources of Fertilizer - Community Comparisons

I focus on the monocropped illaco fields because they seem to be fertilized in a manner distinct from either the other tuber fields or the habas fields. Eight of the ten (80%) Puna Ayllu illaco fields were fertilized, as were five of the eight (62.5%) Ura Ayllu fields. Of the fertilized fields, those in Puna Ayllu received camelid dung and synthetic fertilizer (one field each), and ash (seven of the fields, or 87.5%) (Table 7.15c). In Ura Ayllu one field included sheep dung and guano de isla with the fertilizers, while four fields (80%) were fertilized with ash.

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Analysis of Macronutrients in Illaco Field Fertilizers

The average illaco field in Ura Ayllu received 104 kg of N per hectare, 132 kg/ha of P, and 212 kg/ha of K (Table 7.16c). Fields in Puna Ayllu received considerably less of each macronutrient, with 14 kg/ha of N, 81 kg/ha of P, and 103 kg/ha of K. None of these differences are significant. The difference in NPKtot between the two communities was not significant (Table 7.14c).

FERTILIZATION OF MAIZE FIELDS

There are 66 maize fields documented in this study. All belong to families in Ura Ayllu and are located in either the transitional zone (n=7) or the maizal zone (n=59). The sample includes both monocropped maize (n=32), and maize intercropped with other cultivars (n=34), including various combinations of habas, yacon, common beans, and occasionally, illaco. Table 7.17a summarizes this information. The majority of these fields (85%) were fertilized (Table 7.17b). Only 10 of the 66 had no fertilizer inputs.

Sources of Fertilizers - Comparisons between Croppings and Location

Table 7.18 shows the use of various fertilizers for those fields which were fertilized, dividing the sample according to location (transitional vs. maizal) and crop mix (monocropped vs. polycropped). For all fields, the single most frequently occurring fertilizer is guano de isla (Table 7.18a), present in almost 59% of cases (50% when unfertilized fields are included). Next in importance are cow dung (28.6% of fields), synthetic fertilizers (26.8%), and sheep dung and ash (each 21.4% of fields). When fields located in the transitional zone are compared to those in the maizales, the only large differences appear to be the higher frequency of cow dung in transitional fields (Table 7.18b). With respect to monocropped versus polycropped fields, the only significant difference is more frequent application of synthetic fertilizer in the polycropped maize fields (Table 7.18c).

Analysis of Macronutrients in Maize Field Fertilizers

For the sample of all maize fields which were fertilized, the mean quantity of macronutrients were: 110.44 kg/ha of N, 61.14 kg/ha of P, and 53.49 kg/ha of K. Table 7.19 a and b presents this information for (a) fields in the transitional zone versus maizales zone and (b) monocropped versus polycropped fields, respectively. In neither of these comparisons were significant differences found in the quantities of N, P, and K. Table 7.19c presents the contrasts between the monocropped and polycropped fields in the maizales zone. Although the polycropped fields of the maizales received greater inputs of N, P, and K than did the monocropped fields, none of the differences were significant. It was impossible to create an NPKtot index for the maize fields, because of low correlations between the three individual components.

THE FERTILIZATION OF THE SECOND YEAR OF THE AWI AWI ROTATION

A total of 33 fields in the second year of crop rotation in the Awi Awi manda were documented in this study. Of these, the majority are oca fields (n=29), while three were

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planted in mixed tubers (n=3) and one was planted in monocropped illaco. Neither the mixed tuber fields nor the single illaco fields were fertilized. Of the 29 oca fields, only three (10.3%) were fertilized. All three included camelid dung, one in addition to sheep dung, and one in addition to guano de isla. The typical field in the second year of the Awi Awi rotation receives no additional fertilizer inputs.

SUMMARY AND CONCLUSIONS

This chapter has demonstrated several contrasts in fertilizer use in Cuyo Cuyo. The data help build the definition of production zones. In the preceding chapter it was shown that labor tasks and intensities help to define production zones and cropping cycles. Fertilizer use further distinguishes these differences. Cropping cycles are also fertilization cycles (Mayer 1979).

In the potato fields fertilization is ubiquitous, intense, and complex. Most fields receive fertilization from multiple sources, with significant differences between the two communities. A high proportion of potato fields in Puna Ayllu are fertilized with camelid dung; Ura Ayllu relies heavily on sheep dung. The use of the wanuna in the Ura Ayllu estancia distinguishes it both from Puna Ayllu and from all other zones of potato production used by Ura Aylleños. In both communities, the potato fields of the estancia are fertilized more heavily than fields in other production zones (or other crops). In Ura Ayllu, distant fields are fertilized less heavily than those in the estancia, but there does not seem to be a straightforward, constant relation between distance and fertilizers. There is one exception: greater reliance on synthetic fertilizers in the more distant fields. Ura Aylleños appear to choose fertilizers which, kilo-for-kilo, pack greater nutrient value.

Non-potato crops in the estancia manda are fertilized less frequently, less heavily, and with fewer fertilizer types. The difference in the balance of camelid dung and sheep dung in the two communities persists, but overall in these fields their application is infrequent. For fields which are fertilized, ash is the predominant source in both Puna Ayllu and Ura Ayllu.

Ura Ayllu's maize fields appear more like the potato fields in their high frequency of fertilization (85% of fields). But the most frequently used fertilizer (guano de isla) distinguishes them from both potato and other tuber fields. Cow dung, which appears infrequently in the other sets of fields, is second in importance. Animal dungs occur in the highest frequencies in those fields nearest their grazing areas. Guano de isla, like synthetic fertilizers, is used in the more distant potato fields of Ura Ayllu. At the distances involved--frequently a two hour walk or more--the use of nutrient-dense guano de isla makes good sense.

Cuyo Cuyo soils are generally adequate for agricultural purposes, presumably as a result of careful management. This is the case because agriculture in Cuyo Cuyo includes heavy fertilizer inputs. Agriculture is sustained by these critical inputs, since most of the crops grown in this area (with the exception of nitrogen-fixing habas) deplete soils rapidly of nutrients. In the next chapter I describe the variability of yields and relations between fertilization and agricultural output.